Magick::Image Class
Quick Contents
#BLOBs
BLOBs
#Constructors
Constructors
#Image%20Manipulation%20Methods
Image Manipulation
Methods
#Image%20Attributes
Image Attributes
#Raw%20Image%20Pixel%20Access
Low-Level Image Pixel
Access
Image is the primary object in Magick++ and represents
a single image frame (see
ImageDesign.html
design
). The
STL.html
STL interface
must
be used to operate on
image sequences or images (e.g. of  format  GIF, TIFF, MIFF, Postscript,
& MNG) which are comprized of multiple  image  frames. Individual
frames of a multi-frame image may be requested by adding array-style
notation to the end of the file name (e.g. "animation.gif[3]" retrieves
the fourth frame of a GIF animation.  Various image manipulation
operations may be applied to the image. Attributes may be set on the
image to influence the operation of the manipulation operations. The
Pixels.html
Pixels
class provides low-level access to image
pixels. As a convenience, including
<Magick++.h>
is sufficient in  order to use the complete Magick++ API. The Magick++
API is enclosed within the
Magick
namespace so you must either
add the prefix "
Magick::
" to each class/enumeration name or add
the statement "
using namespace  Magick;
" after including the
Magick++.h
header.
The preferred way to allocate Image objects is via automatic
allocation (on the stack). There is no concern that allocating Image
objects on the   stack will excessively enlarge the stack since Magick++
allocates all large   data objects (such as the actual image data) from
the heap. Use of automatic   allocation is preferred over explicit
allocation (via
new
) since it  is much less error prone and
allows use of C++ scoping rules to avoid memory  leaks. Use of automatic
allocation allows Magick++ objects to be assigned  and copied just like
the C++ intrinsic data types (e.g. '
int
'), leading  to clear and
easy to read code. Use of automatic allocation leads to naturally
exception-safe code since if an exception is thrown, the object is
automatically deallocated once the stack unwinds past the scope of the
allocation (not the case for objects allocated via
new
).
Image is very easy to use. For example, here is a the source to a
program which reads an image, crops it, and writes it to a new file (the
exception handling is optional but strongly recommended):
#include <Magick++.h>
#include <iostream>
using namespace std;
using namespace Magick;
int main(int argc,char **argv)
{
// Construct the image object.
Seperating image construction from the
// the read operation ensures that a
failure to read the image file
// doesn't render the image object
useless.
Image image;
try {
// Read a file into
image object
image.read( "girl.gif" );
// Crop the image to
specified size
(width, height, xOffset, yOffset)
image.crop(
Geometry(100,100, 100, 100) );
// Write the image to
a file
image.write( "x.gif" );
}
catch( Exception &error_ )
{
cout
<< "Caught exception: " << error_.what() << endl;
return 1;
}
return 0;
}
The following is the source to a program which illustrates the use of
Magick++'s efficient reference-counted assignment and copy-constructor
operations which  minimize use of memory and eliminate unncessary copy
operations (allowing   Image objects to be efficiently assigned, and
copied into containers).     The program accomplishes the
following:
Read master image.
Assign master image to second image.
Zoom second image to the size 640x480.
Assign master image to a third image.
Zoom third image to the size 800x600.
Write the second image to a file.
Write the third image to a file.
#include <Magick++.h>
#include <iostream>
using namespace std;
using namespace Magick;
int main(int argc,char **argv)
{
Image
master("horse.jpg");
Image second = master;
second.zoom("640x480");
Image third = master;
third.zoom("800x600");
second.write("horse640x480.jpg");
third.write("horse800x600.jpg");
return 0;
}
During the entire operation, a maximum of three images exist in memory
and the image data is never copied.
The following is the source for another simple program which creates
a 100 by 100 pixel white image with a red pixel in the center and
writes it to a file:
#include <Magick++.h>
using namespace std;
using namespace Magick;
int main(int argc,char **argv)
{
Image image( "100x100",
"white" );
image.pixelColor( 49,
49, "red" );
image.write(
"red_pixel.png" );
return 0;
}
If you wanted to change the color image to grayscale, you could add the
lines:
image.quantizeColorSpace( GRAYColorspace );
image.quantizeColors( 256
);
image.quantize( );
or, more simply:
image.type(
GrayscaleType );
prior to writing the image.
BLOBs
While encoded images (e.g. JPEG) are most often written-to and
read-from a disk file, encoded images may also reside in memory. Encoded
images in   memory are known as BLOBs (Binary Large OBjects) and may be
represented using  the
Blob.html
Blob
class. The encoded
image may be initially placed in memory by reading it  directly from a
file, reading the image from a database, memory-mapped  from  a disk
file, or could be written to memory by Magick++. Once the encoded image
has been placed within a Blob, it may be read into a Magick++ Image via
a
#constructor_blob
constructor
or
#read
read()
. Likewise, a Magick++ image may be written to a Blob via
#write
write()
.
An example of using Image to write to a Blob follows:
#include <Magick++.h>
using namespace std;
using namespace Magick;
int main(int argc,char **argv)
{
// Read GIF file  from
disk
Image image(
"giraffe.gif" );
// Write to BLOB in
JPEG format
Blob blob;
image.magick( "JPEG" )
// Set JPEG output format
image.write( &blob );
[ Use BLOB data (in
JPEG format) here ]
return 0;
}
likewise, to read an image from a Blob, you could use one of the
following examples:
[
Entry condition for the following examples
is that
data
is pointer to encoded image data and
length
represents the size of the data
]
Blob blob( data, length );
Image image( blob );
or
Blob blob( data, length );
Image image;
image.read( blob);
some images do not contain their size or format so the size and format
must be specified in advance:
Blob blob( data, length   );
Image image;
image.size( "640x480")
image.magick( "RGBA" );
image.read( blob);
Constructors
Image may be constructed in a number of ways. It may be constructed
from a file, a URL, or an encoded image (e.g. JPEG) contained in an
in-memory
Blob.html
BLOB
. The available Image
constructors are shown in the following table:
Image Constructors
Signature
Description
const std::string &imageSpec_
Construct Image by reading from file or URL
specified by
imageSpec_
. Use array notation (e.g. filename[9])
to select a  specific scene from a multi-frame image.
const Geometry &size_, const
Color.html
Color
&color_
Construct a blank image canvas of specified
size and  color
const
Blob.html
Blob
&blob_
Construct Image by reading from
encoded image data contained in an in-memory
Blob.html
BLOB
. Depending on the constructor arguments, the Blob
#size
size
,
#depth
depth
,
#magick
magick
(format) may
also be specified. Some image formats require that size  be  specified.
The default ImageMagick uses for depth depends on the compiled-in
Quantum size (8 or 16).  If ImageMagick's Quantum size does not
match that of the image, the depth may need to be specified.
ImageMagick can usually   automatically detect the image's format.
When a format can't be automatically   detected, the format (
#magick
magick
) must be specified.
const
Blob.html
Blob
&blob_, const
Geometry.html
Geometry
&size_
const
Blob.html
Blob
&blob_, const
Geometry.html
Geometry
&size,
unsigned int depth
const
Blob.html
Blob
&blob_, const
Geometry.html
Geometry
&size,
unsigned int depth_, const string &magick_
const
Blob.html
Blob
&blob_, const
Geometry.html
Geometry
&size, const
string &magick_
const unsigned int width_,
const unsigned int height_,
std::string map_,
const
Enumerations.html#StorageType
StorageType
type_,
const void *pixels_
Construct a new Image based on an array of
image pixels.  The pixel data must be in scanline order top-to-bottom.
The data  can be character, short int, integer, float, or double. Float
and double require the pixels to be normalized [0..1]. The other types
are [0..QuantumRange].    For example, to create a 640x480 image from
unsigned red-green-blue character   data, use
Image image( 640, 480,   "RGB",
0, pixels );
The parameters are as follows:
width_
Width in pixels of the image.
height_
Height in pixels of the image.
map_
This character string can be any
combination or  order   of R = red, G = green, B = blue, A = alpha, C =
cyan, Y = yellow M = magenta,   and K = black. The ordering reflects the
order of the pixels  in the supplied   pixel array.
type_
Enumerations.html#StorageType
Pixel
storage    type
(CharPixel, ShortPixel, IntegerPixel, FloatPixel, or
DoublePixel)
pixels_
This array of values contain the pixel
components as  defined by the map_ and type_ parameters. The length of
the arrays must   equal the area specified by the width_ and height_
values and type_ parameters.
Image Manipulation Methods
Image
supports access to all the single-image (versus image-list)
manipulation operations provided by the ImageMagick library. If you
must process a multi-image file (such as an animation), the
STL.html
STL interface
, which provides a multi-image
abstraction on top of
Image
, must   be used.
Image manipulation methods are very easy to use.  For example:
Image image;
image.read("myImage.tiff");
image.addNoise(GaussianNoise);
image.write("myImage.tiff");
adds gaussian noise to the image file "myImage.tiff".
The operations supported by Image are shown in the following table:
Image Image Manipulation Methods
Method
Signature(s)
Description
adaptiveThreshold
unsigned int width,  unsigned
int height, unsigned offset = 0
Apply adaptive thresholding  to
the image. Adaptive thresholding is useful if the ideal threshold level
is not known in advance, or if the illumination gradient is not constant
across the image. Adaptive thresholding works by evaulating the mean
(average) of a pixel region (size specified by
width
and
height
)
and using the mean as the thresholding value. In order to remove
residual noise from the background, the threshold may be adjusted by
subtracting a constant
offset
(default zero) from the mean to
compute the threshold.
addNoise
Enumerations.html#NoiseType
NoiseType
noiseType_
Add noise to image with specified noise type.
affineTransform
const DrawableAffine
&affine
Transform image by
specified affine (or free transform) matrix.
annotate
const std::string &text_, const
Geometry.html
Geometry
&location_
Annotate using specified text, and placement
location
string text_, const
Geometry.html
Geometry
&boundingArea_,
Enumerations.html#GravityType
GravityType
gravity_
Annotate using specified text, bounding area,
and placement  gravity. If
boundingArea_
is invalid, then
bounding area   is entire  image.
const std::string &text_, const
Geometry.html
Geometry
&boundingArea_,
Enumerations.html#GravityType
GravityType
gravity_, double
degrees_,
Annotate with text using specified text,
bounding area,  placement gravity, and rotation. If
boundingArea_
is invalid,   then  bounding area is entire image.
const std::string &text_,
Enumerations.html#GravityType
GravityType
gravity_
Annotate with text (bounding area is entire
image) and placement gravity.
blur
const double radius_ = 1, const double sigma_
= 0.5
Blur image. The
radius_
parameter
specifies the radius of the Gaussian, in pixels, not counting the center
pixel.  The
sigma_
parameter specifies the standard
deviation of the Laplacian,    in pixels.
border
const
Geometry.html
Geometry
&geometry_ = "6x6+0+0"
Border image (add border to image).  The
color of the border is specified by the
borderColor
attribute.
channel
Enumerations.html#ChannelType
ChannelType
layer_
Extract channel from image. Use this option
to extract   a particular channel from  the image.
MatteChannel
for  example, is useful for extracting the opacity values
from an image.
charcoal
const double radius_ = 1, const double sigma_
= 0.5
Charcoal effect image (looks like charcoal
sketch). The
radius_
parameter specifies the radius of the
Gaussian, in pixels,   not counting the center pixel.  The
sigma_
parameter specifies   the standard deviation of the Laplacian, in pixels.
chop
const
Geometry.html
Geometry
&geometry_
Chop image (remove vertical or horizontal
subregion of image)
colorize
const unsigned int opacityRed_, const
unsigned int   opacityGreen_, const unsigned int opacityBlue_, const
Color &penColor_
Colorize image with pen color, using
specified percent   opacity for red, green, and blue quantums.
const unsigned int opacity_, const Color
&penColor_
Colorize image with pen color, using
specified percent   opacity.
comment
const string &comment_
Comment image (add comment string to
image).  By default, each image is commented with its file name.
Use  this     method to  assign a specific comment to the
image.  Optionally   you can include the image filename, type,
width, height, or other  image   attributes by embedding
FormatCharacters.html
special format characters.
compare
const Image &reference_
Compare current image  with
another image. Sets
#meanErrorPerPixel
meanErrorPerPixel
,
#normalizedMaxError
normalizedMaxError
, and
#normalizedMeanError
normalizedMeanError
in the current
image. False is returned if the images are identical. An  ErrorOption
exception is thrown if the reference image columns, rows, colorspace, or
matte differ from the current image.
composite
const
Image.html
Image
&compositeImage_, int xOffset_, int yOffset_,
Enumerations.html#CompositeOperator
CompositeOperator
compose_ =
InCompositeOp
Compose an image onto the current image at
offset specified  by
xOffset_
,
yOffset_
using the
composition algorithm   specified  by
compose_
.
const
Image.html
Image
&compositeImage_, const
Geometry.html
Geometry
&offset_,
Enumerations.html#CompositeOperator
CompositeOperator
compose_ =
InCompositeOp
Compose an image onto the current image at
offset specified  by
offset_
using the composition algorithm
specified by
compose_
.
const
Image.html
Image
&compositeImage_,
Enumerations.html#GravityType
GravityType
gravity_,
Enumerations.html#CompositeOperator
CompositeOperator
compose_ =
InCompositeOp
Compose an image onto the current image with
placement specified by
gravity_
using the composition algorithm
specified by
compose_
.
contrast
unsigned int sharpen_
Contrast image (enhance intensity differences
in image)
convolve
unsigned int order_, const double *kernel_
Convolve image.  Applies a user-specfied
convolution to the image. The
order_
parameter represents the
number of columns    and rows in the filter kernel, and
kernel_
is a two-dimensional array  of doubles representing the convolution
kernel to apply.
crop
const
Geometry.html
Geometry
&geometry_
Crop image (subregion of original image)
cycleColormap
int amount_
Cycle image colormap
despeckle
void
Despeckle image (reduce speckle noise)
display
void
Display image on screen.
Caution:
if
an image format is is not compatible   with the display visual (e.g.
JPEG on a colormapped display) then the original   image will be
altered. Use a copy of the original if this is a problem.
draw
const
Drawable.html
Drawable
&drawable_
Draw shape or text on image.
const std::list<
Drawable.html
Drawable
> &drawable_
Draw shapes or text on image using a set of
Drawable objects contained in an STL list. Use of this method improves
drawing performance    and allows batching draw objects together in a
list for repeated use.
edge
unsigned int radius_ = 0.0
Edge image (hilight edges in image).
The radius   is the radius of the pixel neighborhood.. Specify a radius
of zero for automatic  radius selection.
emboss
const double radius_ = 1, const double sigma_
= 0.5
Emboss image (hilight edges with 3D effect).
The
radius_
parameter specifies the radius of the Gaussian, in
pixels, not  counting the center pixel.  The
sigma_
parameter specifies the  standard deviation of the Laplacian, in pixels.
enhance
void
Enhance image (minimize noise)
equalize
void
Equalize image (histogram equalization)
erase
void
Set all image pixels to the current
background color.
flip
void
Flip image (reflect each scanline in the
vertical direction)
floodFill-
Color
unsigned int x_, unsigned int y_, const
Color.html
Color
&fillColor_
Flood-fill color across pixels
that match   the color of the target pixel and are neighbors of the
target pixel.  Uses   current fuzz setting when determining color match.
const
Geometry.html
Geometry
&point_, const
Color.html
Color
&fillColor_
unsigned int x_, unsigned int y_, const
Color.html
Color
&fillColor_, const
Color.html
Color
&borderColor_
Flood-fill color across pixels
starting at target-pixel and stopping at pixels matching specified
border color. Uses  current fuzz setting when determining color match.
const
Geometry.html
Geometry
&point_, const
Color.html
Color
&fillColor_, const
Color.html
Color
&borderColor_
floodFillOpacity
const long x_, const long y_, const unsigned
int opacity_,  const PaintMethod method_
Floodfill pixels matching color (within fuzz
factor) of target pixel(x,y) with replacement opacity value using method.
floodFill-
Texture
unsigned int x_, unsigned int y_,  const
Image &texture_
Flood-fill texture across pixels
that match  the color of the target pixel and are neighbors of the
target pixel.   Uses  current fuzz setting when determining color match.
const
Geometry.html
Geometry
&point_, const Image &texture_
unsigned int x_, unsigned int y_, const Image
&texture_, const
Color.html
Color
&borderColor_
Flood-fill texture across pixels
starting at target-pixel and stopping at pixels matching specified
border color.  Uses current fuzz setting when determining color match.
const
Geometry.html
Geometry
&point_, const Image &texture_, const
Color.html
Color
&borderColor_
flop
void
Flop image (reflect each scanline in the
horizontal direction)
frame
const
Geometry.html
Geometry
&geometry_ = "25x25+6+6"
Add decorative frame around image
unsigned int width_, unsigned int height_,
int x_,   int  y_, int innerBevel_ = 0, int outerBevel_ = 0
gamma
double gamma_
Gamma correct image (uniform red, green, and
blue correction).
double gammaRed_, double gammaGreen_, double
gammaBlue_
Gamma correct red, green, and blue channels
of image.
gaussianBlur
const double width_, const double sigma_
Gaussian blur image. The number of neighbor
pixels to be included in the convolution mask is specified by
'width_'.  For   example, a width of one gives a (standard) 3x3
convolution mask. The standard   deviation of the gaussian bell curve is
specified by 'sigma_'.
implode
const double factor_
Implode image (special effect)
label
const string &label_
Assign a label to an image. Use this option
to  assign  a  specific label to the image. Optionally
you can include    the image filename, type, width, height, or scene
number in the label by   embedding
FormatCharacters.html
special format characters.
If the first character of string is @, the
image label is read from a  file titled by the remaining characters in
the string. When converting to Postscript, use this  option to
specify a header string to print above the image.
level
const double black_point,
const double white_point, const double mid_point=1.0
Level image. Adjust the
levels of the image by scaling the colors falling between specified
white and black points to the full available quantum range. The
parameters provided represent the black, mid (gamma), and white
points.  The black point specifies the darkest color in the image.
Colors darker than the black point are set to zero. Mid point (gamma)
specifies a gamma correction to apply to the image. White point
specifies the lightest color in the image.  Colors brighter than
the white point are set to the maximum quantum value. The black and
white point have the valid range 0 to QuantumRange while mid (gamma) has a
useful range of 0 to ten.
levelChannel
const ChannelType
channel, const double black_point, const double white_point, const
double mid_point=1.0
Level image channel.
Adjust the levels of the image channel by scaling the values falling
between specified white and black points to the full available quantum
range. The parameters provided represent the black, mid (gamma), and
white points. The black point specifies the darkest color in the image.
Colors darker than the black point are set to zero. Mid point (gamma)
specifies a gamma correction to apply to the image. White point
specifies the lightest color in the image. Colors brighter than the
white point are set to the maximum quantum value. The black and white
point have the valid range 0 to QuantumRange while mid (gamma) has a useful
range of 0 to ten.
magnify
void
Magnify image by integral size
map
const Image &mapImage_ , bool dither_ =
false
Remap image colors with closest color from
reference image. Set dither_ to
true
in to apply Floyd/Steinberg
error diffusion    to the image. By default, color reduction chooses an
optimal  set     of colors that best represent the original
image. Alternatively, you can  choose  a
particular  set  of colors  from     an image file
with this option.
matteFloodfill
const
Color.html
Color
&target_, const unsigned int  opacity_, const int x_, const int
y_,
Enumerations.html#PaintMethod
PaintMethod
method_
Floodfill designated area with a replacement
opacity value.
medianFilter
const double radius_ = 0.0
Filter image by replacing each pixel
component with   the median color in a circular neighborhood
minify
void
Reduce image by integral size
modifyImage
void
Prepare to update image. Ensures that there
is only   one reference to the underlying image so that the underlying
image may be   safely modified without effecting previous generations of
the image. Copies   the underlying image to a new image if necessary.
modulate
double brightness_, double saturation_,
double hue_
Modulate percent hue, saturation, and
brightness of  an image. Modulation of saturation and brightness is as a
ratio of the current value (1.0 for no change). Modulation of hue is an
absolute rotation of -180 degrees to +180 degrees from the current
position corresponding to an argument range of 0 to 2.0 (1.0 for no
change).
negate
bool grayscale_ = false
Negate colors in image.  Replace every
pixel with  its complementary color (white becomes black, yellow becomes
blue, etc.).   Set grayscale to only negate grayscale values in
image.
normalize
void
Normalize image (increase contrast by
normalizing the  pixel values to span the full range of color values).
oilPaint
unsigned int radius_ = 3
Oilpaint image (image looks like oil painting)
opacity
unsigned int opacity_
Set or attenuate the opacity channel in the
image. If the image pixels are opaque then they are set to the specified
opacity value, otherwise they are blended with the supplied opacity
value.  The value of opacity_ ranges from 0 (completely opaque) to
QuantumRange
. The defines
OpaqueOpacity
and
TransparentOpacity
are
available to specify completely opaque or completely transparent,
respectively.
opaque
const
Color.html
Color
&opaqueColor_, const
Color.html
Color
&penColor_
Change color of pixels matching opaqueColor_
to specified   penColor_.
ping
const std::string &imageSpec_
Ping is similar to read
except only enough of the image is read to determine the image columns,
rows, and   filesize.  The
#columns
columns
,
#rows
rows
, and
#fileSize
fileSize
attributes are valid after invoking ping.  The image data is not
valid after calling ping.
const Blob &blob_
process
std::string name_,
const int argc_, char **argv_
Execute the named
process module, passing any arguments via an argument vector, with argc_
specifying the number of arguments in the vector, and argv_ passing the
address of an array of null-terminated C strings which constitute the
argument vector. An exception is thrown if the requested process module
does not exist, fails to load, or fails during execution.
quantize
bool measureError_ = false
Quantize image (reduce number of colors). Set
measureError_ to true in order to calculate error attributes.
raise
const
Geometry.html
Geometry
&geometry_ = "6x6+0+0",  bool raisedFlag_ =  false
Raise image (lighten or darken the edges of
an image   to give a 3-D raised or lowered effect)
read
const string &imageSpec_
Read image into current object
const
Geometry.html
Geometry
&size_, const std::string &imageSpec_
Read image of specified size into current
object. This  form is useful for images that do not specifiy their size
or to specify   a size hint for decoding an image. For example, when
reading a Photo CD,  JBIG, or JPEG image, a size request causes the
library to return an image  which is the next resolution greater or
equal to the specified size. This  may result in memory and time savings.
const
Blob.html
Blob
&blob_
Read encoded image of specified
size from  an in-memory
Blob.html
BLOB
into current
object. Depending on the method arguments, the Blob size,   depth, and
format may also be specified. Some image formats require that  size be
specified. The default ImageMagick uses for depth depends on its
Quantum size (8 or 16).  If ImageMagick's Quantum size does not
match that of the image, the depth may need to be specified.
ImageMagick can usually automatically detect the image's format. When
a format can't be automatically detected, the format must be specified.
const
Blob.html
Blob
&blob_, const
Geometry.html
Geometry
&size_
const
Blob.html
Blob
&blob_, const
Geometry.html
Geometry
&size_,
unsigned int depth_
const
Blob.html
Blob
&blob_, const
Geometry.html
Geometry
&size_,
unsigned short depth_, const string &magick_
const
Blob.html
Blob
&blob_, const
Geometry.html
Geometry
&size_, const
string &magick_
const unsigned int width_, const unsigned int
height_, std::string map_, const StorageType type_, const void *pixels_
Read image based on an array of image pixels.
The pixel  data must be in scanline order top-to-bottom. The data can be
character, short int, integer, float, or double. Float and double
require the pixels   to be normalized [0..1]. The other types are
[0..QuantumRange].  For example,   to create a 640x480 image from
unsigned red-green-blue character data, use
image.read( 640, 480, "RGB",   0,
pixels );
The parameters are as follows:
width_
Width in pixels of the image.
height_
Height in pixels of the image.
map_
This character string can be any
combination or  order   of R = red, G = green, B = blue, A = alpha, C =
cyan, Y = yellow M = magenta,   and K = black. The ordering reflects the
order of the pixels  in the supplied   pixel array.
type_
Pixel storage type (CharPixel,
ShortPixel, IntegerPixel,    FloatPixel, or DoublePixel)
pixels_
This array of values contain the pixel
components as  defined by the map_ and type_ parameters. The length of
the arrays must   equal the area specified by the width_ and height_
values and type_ parameters.
reduceNoise
void
Reduce noise in image using a
noise peak   elimination filter.
unsigned int order_
roll
int columns_, int rows_
Roll image (rolls image vertically and
horizontally) by specified number of columnms and rows)
rotate
double degrees_
Rotate image counter-clockwise by specified
number of degrees.
sample
const
Geometry.html
Geometry
&geometry_
Resize image by using pixel sampling algorithm
scale
const
Geometry.html
Geometry
&geometry_
Resize image by using simple ratio algorithm
segment
double clusterThreshold_ = 1.0,
double smoothingThreshold_ = 1.5
Segment (coalesce similar image components)
by analyzing   the histograms of the color components and identifying
units that are homogeneous   with the fuzzy c-means technique. Also uses
quantizeColorSpace
and
verbose
image attributes. Specify
clusterThreshold_
,
as the number  of  pixels  each cluster  must exceed
the cluster threshold to be considered valid.
SmoothingThreshold_
eliminates noise in the  second derivative of the histogram. As the
value is  increased, you can  expect  a  smoother
second derivative.  The default is 1.5.
shade
double azimuth_ = 30, double elevation_ = 30,
bool colorShading_ = false
Shade image using distant light source.
Specify
azimuth_
and
elevation_
as the
position  of   the light source. By default, the shading
results as a grayscale image.. Set c
olorShading_
to
true
to
shade the  red, green, and blue components of the image.
sharpen
const double radius_ = 1, const double sigma_
= 0.5
Sharpen pixels in image.  The
radius_
parameter specifies the radius of the Gaussian, in pixels, not counting
the center pixel.  The
sigma_
parameter specifies the
standard deviation of the Laplacian, in pixels.
shave
const Geometry &geometry_
Shave pixels from image edges.
shear
double xShearAngle_, double yShearAngle_
Shear image (create parallelogram by sliding
image by X or Y axis).  Shearing slides one edge of an image along
the X     or  Y axis,  creating  a
parallelogram.  An X direction    shear slides an edge along the X
axis, while  a  Y  direction    shear  slides
an edge along the Y axis.  The amount of the  shear is controlled
by a shear angle.  For X direction  shears,     x
degrees is measured relative to the Y axis, and similarly, for Y
direction shears  y  degrees is measured relative to the X
axis. Empty triangles left over from shearing the  image  are
filled  with  the  color  defined as
borderColor
.
solarize
double factor_ = 50.0
Solarize image (similar to effect seen when
exposing a photographic film to light during the development process)
spread
unsigned int amount_ = 3
Spread pixels randomly within image by
specified amount
stegano
const Image &watermark_
Add a digital watermark to the image (based
on second   image)
stereo
const Image &rightImage_
Create an image which appears in stereo when
viewed with red-blue glasses (Red image on left, blue on right)
swirl
double degrees_
Swirl image (image pixels are rotated by
degrees)
texture
const Image &texture_
Layer a texture on pixels matching image
background color.
threshold
double threshold_
Threshold image
transform
const
Geometry.html
Geometry
&imageGeometry_
Transform image based on image
and crop   geometries. Crop geometry is optional.
const
Geometry.html
Geometry
&imageGeometry_, const
Geometry.html
Geometry
&cropGeometry_
transparent
const
Color.html
Color
&color_
Add matte image to image, setting pixels
matching color  to transparent.
trim
void
Trim edges that are the background color from
the image.
unsharpmask
double radius_, double sigma_, double
amount_, double   threshold_
Replace image with a sharpened version of the
original image using the unsharp mask algorithm. The
radius
_
parameter specifies    the radius of the Gaussian, in pixels, not
counting the center pixel. The
sigma
_ parameter specifies the
standard deviation   of the Gaussian, in pixels. The
amount
_
parameter specifies the percentage   of the difference between the
original and the blur image that is added back into the original. The
threshold
_
parameter specifies the threshold   in pixels needed to apply the
diffence amount.
wave
double amplitude_ = 25.0, double wavelength_
= 150.0
Alter an image along a sine wave.
write
const string &imageSpec_
Write image to a file using filename i
mageSpec_
.
Caution:
if
an image format is selected which is   capable of supporting fewer
colors than the original image or quantization   has been requested, the
original image will be quantized to fewer colors.   Use a copy of the
original if this is a problem.
Blob.html
Blob
*blob_
Write image to a in-memory
Blob.html
BLOB
stored in
blob_
. The
magick
_
parameter specifies the image   format to write (defaults to
#magick
magick
). The depth_ parameter species the image
depth (defaults to
#depth
depth
).
Caution:
if
an image format is selected which is   capable of supporting fewer
colors than the original image or quantization   has been requested, the
original image will be quantized to fewer colors.   Use a copy of the
original if this is a problem.
Blob.html
Blob
*blob_,
std::string &magick_
Blob.html
Blob
*blob_,
std::string &magick_, unsigned int depth_
const int x_, const int y_, const unsigned
int columns_,    const unsigned int rows_, const std::string &map_,
const StorageType   type_, void *pixels_
Write pixel data into a buffer you supply.
The data   is saved either as char, short int, integer, float or double
format in the   order specified by the type_ parameter. For example, we
want to extract scanline 1 of a 640x480 image as character data in
red-green-blue order:
image.write(0,0,640,1,"RGB",0,pixels);
The parameters are as follows:
x_
Horizontal ordinate of left-most
coordinate of region   to extract.
y_
Vertical ordinate of top-most
coordinate of region   to extract.
columns_
Width in pixels of the region to
extract.
rows_
Height in pixels of the region to
extract.
map_
This character string can be any
combination or  order   of R = red, G = green, B = blue, A = alpha, C =
cyan, Y = yellow,  M = magenta,   and K = black. The ordering reflects
the order of the pixels  in the supplied   pixel array.
type_
Pixel storage type (CharPixel,
ShortPixel, IntegerPixel,    FloatPixel, or DoublePixel)
pixels_
This array of values contain the pixel
components as  defined by the map_ and type_ parameters. The length of
the arrays must   equal the area specified by the width_ and height_
values and type_ parameters.
zoom
const
Geometry.html
Geometry
&geometry_
Zoom image to specified size.
Image Attributes
Image attributes are set and obtained via methods in Image. Except for
methods which accept pointer arguments (e.g. c
hromaBluePrimary)
all methods return attributes by value.
Image attributes are easily used. For example, to set the resolution
of the TIFF file "file.tiff" to 150 dots-per-inch (DPI) in both the
horizontal and vertical directions, you can use the following example
code:
string filename("file.tiff");
Image image;
image.read(filename);
image.resolutionUnits(PixelsPerInchResolution);
image.density(Geometry(150,150));
// could also use image.density("150x150")
image.write(filename)
The supported image attributes and the method arguments required to
obtain them are shown in the following table:
Image Attributes
Function
Type
Get Signature
Set Signature
Description
adjoin
bool
void
bool flag_
Join images into a single multi-image file.
antiAlias
bool
void
bool flag_
Control antialiasing of rendered Postscript
and Postscript   or TrueType fonts. Enabled by default.
animation-
Delay
unsigned int (0 to 65535)
void
unsigned int delay_
Time in 1/100ths of a second (0 to 65535)
which must   expire before displaying the next image in an animated
sequence. This  option   is useful for regulating the animation of a
sequence  of GIF  images  within Netscape.
animation-
Iterations
unsigned int
void
unsigned int iterations_
Number of iterations to loop an animation
(e.g. Netscape   loop extension) for.
attribute
string
const
std::string name_
const
std::string name_, const std::string value_
An arbitrary named
image attribute. Any number of named attributes may be attached to the
image. For example, the image comment is a named image attribute with
the name "comment". EXIF tags are attached to the image as named
attributes. Use the syntax "[EXIF:<tag>]" to request an EXIF tag
similar to "[EXIF:DateTime]".
background-
Color
Color.html
Color
void
const
Color.html
Color
&color_
Image background color
background-
Texture
string
void
const string &texture_
Image file name to use as the background
texture. Does  not modify image pixels.
baseColumns
unsigned int
void
Base image width (before transformations)
baseFilename
string
void
Base image filename (before transformations)
baseRows
unsigned int
void
Base image height (before transformations)
borderColor
Color.html
Color
void
const
Color.html
Color
&color_
Image border color
boundingBox
Geometry
void
Return smallest bounding box enclosing
non-border pixels.  The current fuzz value is used when discriminating
between pixels.   This is the crop bounding box used by
crop(Geometry(0,0)).
boxColor
Color.html
Color
void
const
Color.html
Color
&boxColor_
Base color that annotation text is rendered
on.
cacheThreshold
unsigned int
const int
Pixel cache threshold in megabytes. Once this
threshold is exceeded, all subsequent pixels cache operations are
to/from disk. This    is a static method and the attribute it sets is
shared by all Image objects.
channelDepth
unsigned
int
const
ChannelType channel_
const ChannelType
channel_, const unsigned int depth_
Channel modulus depth.
The channel modulus depth represents the minimum number of bits required
to support the channel without loss. Setting the channel's modulus depth
modifies the channel (i.e. discards resolution) if the requested modulus
depth is less than the current modulus depth, otherwise the channel is
not altered. There is no attribute associated with the modulus depth so
the current modulus depth is obtained by inspecting the pixels. As a
result, the depth returned may be less than the most recently set
channel depth. Subsequent image processing may result in increasing the
channel depth.
chroma-
BluePrimary
double x & y
double *x_, double *y_
double x_, double y_
Chromaticity blue primary point (e.g. x=0.15,
y=0.06)
chroma-
GreenPrimary
double x & y
double *x_, double *y_
double x_, double y_
Chromaticity green primary point (e.g. x=0.3,
y=0.6)
chroma-
RedPrimary
double x & y
double *x_, double *y_
double x_, double y_
Chromaticity red primary point (e.g. x=0.64,
y=0.33)
chroma-
WhitePoint
double x & y
double*x_, double *y_
double x_, double y_
Chromaticity white point (e.g. x=0.3127,
y=0.329)
classType
Enumerations.html#ClassType
ClassType
void
Enumerations.html#ClassType
ClassType
class_
Image storage class.  Note that
conversion from   a DirectClass image to a PseudoClass image may result
in a loss of  color  due to the limited size of the palette (256 or
65535 colors).
clipMask
Image
void
const Image &clipMask_
Associate a clip mask image with the current
image. The clip mask image must have the same dimensions as the current
image or   an exception is thrown. Clipping occurs wherever pixels are
transparent in  the clip mask image. Clipping Pass an invalid image to
unset an existing   clip mask.
colorFuzz
double
void
double fuzz_
Colors within this distance are considered
equal. A number of algorithms search for a target  color. By
default the color   must be exact. Use this option to match colors that
are close to the target    color in RGB space.
colorMap
Color.html
Color
unsigned int index_
unsigned int index_, const
Color.html
Color
&color_
Color at colormap index.
colorMapSize
unsigned int
void
unsigned int entries_
Number of entries in the
colormap. Setting the colormap size may extend or truncate the colormap.
The maximum number of supported entries is specified by the
MaxColormapSize
constant,
and is dependent on the value of QuantumDepth when ImageMagick is
compiled. An exception is thrown if more entries are requested than may
be supported. Care should be taken when truncating the colormap to
ensure that the image colormap indexes reference valid colormap entries.
colorSpace
Enumerations.html#ColorspaceType
ColorspaceType
colorSpace_
void
Enumerations.html#ColorspaceType
ColorspaceType
colorSpace_
The colorspace (e.g. CMYK) used to represent
the image  pixel colors. Image pixels are always stored as RGB(A) except
for the case  of CMY(K).
columns
unsigned int
void
Image width
comment
string
void
Image comment
compose
Enumerations.html#CompositeOperator
CompositeOperator
void
Enumerations.html#CompositeOperator
CompositeOperator
compose_
Composition operator to be used when
composition is implicitly used (such as for image flattening).
compress-
Type
Enumerations.html#CompressionType
CompressionType
void
Enumerations.html#CompressionType
CompressionType
compressType_
Image compresion type. The default is the
compression type of the specified image file.
debug
bool
void
bool flag_
Enable printing of internal debug messages
from ImageMagick   as it executes.
defineValue
string
const std::string
&magick_, const std::string &key_
const std::string
&magick_, const std::string &key_,  const std::string
&value_
Set or obtain a
definition string to applied when encoding or decoding the specified
format. The meanings of the definitions are format specific. The format
is designated by the
magick_
argument, the format-specific key is designated by
key_
, and the associated value is
specified by
value_
. See the
defineSet() method if the key must be removed entirely.
defineSet
bool
const std::string
&magick_, const std::string &key_
const std::string
&magick_, const std::string &key_, bool flag_
Set or obtain a
definition flag to applied when encoding or decoding the specified
format.
. Similar to the defineValue() method except that
passing the
flag_
value 'true'
creates a value-less define with that format and key. Passing the
f
lag_
value 'false' removes any existing matching definition. The method
returns 'true' if a matching key exists, and 'false' if no matching key
exists.
density
Geometry.html
Geometry
(default 72x72)
void
const
Geometry.html
Geometry
&density_
Vertical and horizontal resolution in pixels
of the  image. This option specifies an image density when decoding a
Postscript or Portable Document page. Often used with
psPageSize
.
depth
unsigned int (8, 16, or 32)
void
unsigned int depth_
Image depth. Used to specify the bit depth
when reading   or writing  raw images or when the output format
supports multiple depths. Defaults to the quantum depth that
ImageMagick is compiled with.
endian
Enumerations.html#EndianType
EndianType
void
Enumerations.html#EndianType
EndianType
endian_
Specify (or obtain) endian option for formats
which support it.
directory
string
void
Tile names from within an image montage
fileName
string
void
const string &fileName_
Image file name.
fileSize
off_t
void
Number of bytes of the image on disk
fillColor
Color
void
const Color &fillColor_
Color to use when filling drawn objects
fillPattern
Image
void
const Image &fillPattern_
Pattern image to use when filling drawn
objects.
fillRule
Enumerations.html#FillRule
FillRule
void
const Magick::FillRule &fillRule_
Rule to use when filling drawn objects.
filterType
Enumerations.html#FilterTypes
FilterTypes
void
Enumerations.html#FilterTypes
FilterTypes
filterType_
Filter to use when resizing image. The
reduction filter  employed has a sigificant effect on the time required
to resize an  image and the resulting quality. The default filter is
Lanczos
which has been shown to produce high quality results when reducing most
images.
font
string
void
const string &font_
Text rendering font. If the font is a fully
qualified X server font name, the font is obtained from an X
server. To use  a TrueType font, precede the TrueType filename with an
@. Otherwise, specify     a  Postscript font name (e.g.
"helvetica").
fontPointsize
unsigned int
void
unsigned int pointSize_
Text rendering font point size
fontTypeMetrics
TypeMetric.html
TypeMetric
const std::string &text_,
TypeMetric.html
TypeMetric
*metrics
Update metrics with font type metrics using
specified
text
, and current
#font
font
and
#fontPointsize
fontPointSize
settings.
format
string
void
Long form image format description.
gamma
double (typical range 0.8 to 2.3)
void
Gamma level of the image. The same color
image displayed   on two different  workstations  may
look  different  due to differences in the display monitor.
Use gamma correction    to  adjust  for this
color  difference.
geometry
Geometry.html
Geometry
void
Preferred size of the image when encoding.
gifDispose-
Method
unsigned int
{ 0 = Disposal not specified,
1 = Do not dispose of graphic,
3 = Overwrite graphic with background   color,
4 = Overwrite graphic with previous   graphic. }
void
unsigned int disposeMethod_
GIF disposal method. This option is used to
control how successive frames are rendered (how the preceding frame is
disposed of)  when creating a GIF animation.
iccColorProfile
Blob.html
Blob
void
const
Blob.html
Blob
&colorProfile_
ICC color profile. Supplied via a
Blob.html
Blob
since Magick++/ and ImageMagick do not
currently support formating this   data structure directly.
Specifications are available from the
http://www.color.org/
International Color Consortium
for the format of ICC color profiles.
interlace-
Type
Enumerations.html#InterlaceType
InterlaceType
void
Enumerations.html#InterlaceType
InterlaceType
interlace_
The type of interlacing scheme (default
NoInterlace
). This option is used to specify the type of  interlacing
scheme  for  raw  image formats such as RGB or YUV.
NoInterlace
means do not  interlace,
LineInterlace
uses scanline
interlacing, and
PlaneInterlace
uses plane interlacing.
PartitionInterlace
is like
PlaneInterlace
except the
different planes  are saved  to individual  files (e.g.
image.R, image.G, and image.B). Use
LineInterlace
or
PlaneInterlace
to create an interlaced GIF or progressive JPEG image.
iptcProfile
Blob.html
Blob
void
const
Blob.html
Blob
&
iptcProfile_
IPTC profile. Supplied via a
Blob.html
Blob
since Magick++ and ImageMagick do not
currently  support formating   this data structure directly.
Specifications are available from the
http://www.iptc.org/
International Press Telecommunications Council
for IPTC profiles.
label
string
void
const string &label_
Image label
magick
string
void
const string &magick_
Get image format (e.g. "GIF")
matte
bool
void
bool matteFlag_
True if the image has transparency. If set
True, store  matte channel if  the image has one otherwise create
an opaque  one.
matteColor
Color.html
Color
void
const
Color.html
Color
&matteColor_
Image matte (frame) color
meanError-
PerPixel
double
void
The mean error per pixel computed when an
image is  color reduced. This parameter is only valid if verbose is set
to true  and  the image has just been quantized.
modulusDepth
unsigned
int
void
unsigned
int depth_
Image
modulus depth (minimum number of bits required to support
red/green/blue components without loss of accuracy). The pixel modulus
depth may be decreased by supplying a value which is less than the
current value, updating the pixels (reducing accuracy) to the new depth.
The pixel modulus depth can not be increased over the current value
using this method.
monochrome
bool
void
bool flag_
Transform the image to black and white
montage-
Geometry
Geometry.html
Geometry
void
Tile size and offset within an image montage.
Only valid for montage images.
normalized-
MaxError
double
void
The normalized max error per pixel computed
when an  image is color reduced. This parameter is only valid if verbose
is set  to  true and the image has just been quantized.
normalized-
MeanError
double
void
The normalized mean error per pixel computed
when an  image is color reduced. This parameter is only valid if verbose
is set   to true and the image has just been quantized.
packets
unsigned int
void
The number of runlength-encoded packets in
the image
packetSize
unsigned int
void
The number of bytes in each pixel packet
page
Geometry.html#PostscriptPageSize
Geometry
void
const
Geometry.html#PostscriptPageSize
Geometry
&pageSize_
Preferred size and location of an image
canvas.
Use this option to specify the   dimensions
and position of the Postscript page in dots per inch or a TEXT   page in
pixels. This option is typically used in concert with
#density
density
.
Page may also be used to position   a GIF
image (such as for a scene in an animation)
pixelColor
Color.html
Color
unsigned int x_, unsigned int y_
unsigned int x_, unsigned int y_, const
Color.html
Color
&color_
Get/set pixel color at location x & y.
profile
Blob.html
Blob
const std::string name_
const std::string name_,   const Blob
&colorProfile_
Get/set/remove
a named
profile
. Valid names include
"*",
"8BIM", "ICM", "IPTC", or a user/format-defined profile name.
quality
unsigned int (0 to 100)
void
unsigned int quality_
JPEG/MIFF/PNG compression level (default 75).
quantize-
Colors
unsigned int
void
unsigned int colors_
Preferred number of colors in the image. The
actual number of colors in the image may be less than your request, but
never more.   Images with less unique colors than specified with this
option will have  any duplicate or unused colors removed.
quantize-
ColorSpace
Enumerations.html#ColorspaceType
ColorspaceType
void
Enumerations.html#ColorspaceType
ColorspaceType
colorSpace_
Colorspace to quantize colors in (default
RGB). Empirical   evidence suggests that distances in color spaces such
as YUV or YIQ correspond   to perceptual color differences more closely
than do distances in RGB space.   These color spaces may give better
results when color reducing an image.
quantize-
Dither
bool
void
bool flag_
Apply Floyd/Steinberg error diffusion to the
image. The basic strategy of dithering is to  trade  intensity
resolution  for  spatial  resolution  by
averaging the intensities     of  several
neighboring  pixels. Images which  suffer     from
severe  contouring  when  reducing colors can  be
improved with this option. The quantizeColors or monochrome option must
be set for this option to take effect.
quantize-
TreeDepth
unsigned int
void
unsigned int treeDepth_
Depth of the quantization color
classification tree.   Values of 0 or 1 allow selection of the optimal
tree depth for the color  reduction algorithm. Values between 2 and 8
may be used to manually adjust  the tree depth.
rendering-
Intent
Enumerations.html#RenderingIntent
RenderingIntent
void
Enumerations.html#RenderingIntent
RenderingIntent
render_
The type of rendering intent
resolution-
Units
Enumerations.html#ResolutionType
ResolutionType
void
Enumerations.html#ResolutionType
ResolutionType
units_
Units of image resolution
rows
unsigned int
void
The number of pixel rows in the image
scene
unsigned int
void
unsigned int scene_
Image scene number
signature
string
bool force_ = false
Image MD5 signature. Set force_ to 'true' to
force re-computation of signature.
size
Geometry.html
Geometry
void
const
Geometry.html
Geometry
&geometry_
Width and height of a raw image (an image
which does   not support width and height information).  Size may
also be used to  affect the image size read from a multi-resolution
format (e.g. Photo CD,  JBIG, or JPEG.
strokeAntiAlias
bool
void
bool flag_
Enable or disable anti-aliasing when drawing
object outlines.
strokeColor
Color
void
const Color &strokeColor_
Color to use when drawing object outlines
strokeDashOffset
unsigned int
void
double strokeDashOffset_
While drawing using a dash pattern, specify
distance into the dash pattern to start the dash (default 0).
strokeDashArray
const double*
void
const double* strokeDashArray_
Specify the pattern of dashes and gaps used
to stroke   paths. The strokeDashArray represents a zero-terminated
array of numbers  that specify the lengths (in pixels) of alternating
dashes and gaps in user  units. If an odd number of values is provided,
then the list of values is  repeated to yield an even number of
values.  A typical strokeDashArray_   array might contain the
members 5 3 2 0, where the zero value indicates the  end of the pattern
array.
strokeLineCap
LineCap
void
LineCap lineCap_
Specify the shape to be used at the corners
of paths   (or other vector shapes) when they are stroked. Values of
LineJoin are UndefinedJoin,  MiterJoin, RoundJoin, and BevelJoin.
strokeLineJoin
LineJoin
void
LineJoin lineJoin_
Specify the shape to be used at the corners
of paths   (or other vector shapes) when they are stroked. Values of
LineJoin are UndefinedJoin,  MiterJoin, RoundJoin, and BevelJoin.
strokeMiterLimit
unsigned int
void
unsigned int miterLimit_
Specify miter limit. When two line segments
meet at  a sharp angle and miter joins have been specified for
'lineJoin', it is possible  for the miter to extend far beyond the
thickness of the line stroking the  path. The miterLimit' imposes a
limit on the ratio of the miter length to  the 'lineWidth'. The default
value of this parameter is 4.
strokeWidth
double
void
double strokeWidth_
Stroke width for use when drawing vector
objects (default  one)
strokePattern
Image
void
const Image &strokePattern_
Pattern image to use while drawing object
stroke (outlines).
subImage
unsigned int
void
unsigned int subImage_
Subimage of an image sequence
subRange
unsigned int
void
unsigned int subRange_
Number of images relative to the base image
textEncoding
string
void
const std::string &encoding_
Specify the code set to  use for text
annotations. The only character encoding which may be specified   at
this time is "UTF-8" for representing
http://www.unicode.org/
Unicode
as a
sequence of bytes. Specify  an  empty string to use the default ASCII
encoding. Successful text annotation   using Unicode may require fonts
designed to support Unicode.
tileName
string
void
const string &tileName_
Tile name
totalColors
unsigned long
void
Number of colors in the image
type
Enumerations.html#ImageType
ImageType
void
Enumerations.html#ImageType
ImageType
Image type.
verbose
bool
void
bool verboseFlag_
Print detailed information about the image
view
string
void
const string &view_
FlashPix viewing parameters.
x11Display
string (e.g. "hostname:0.0")
void
const string &display_
X11 display to display to, obtain fonts from,
or to  capture image from
xResolution
double
void
x resolution of the image
yResolution
double
void
y resolution of the image
Low-Level Image Pixel Access
Image pixels (of type
PixelPacket.html
PixelPacket
)
may be accessed directly via the
Image Pixel   Cache
.  The
image pixel cache is a rectangular window into the  actual image pixels
(which may be in memory, memory-mapped from a disk file,  or entirely on
disk). Two interfaces exist to access the
Image Pixel Cache.
The
interface described here (part of the
Image
class) supports only
one view at a time. See the
Pixels.html
Pixels
class for a more abstract interface which supports   simultaneous pixel
views (up to the number of rows). As an analogy, the interface described
here relates to the
Pixels.html
Pixels
class as
stdio's gets() relates to fgets(). The
Pixels.html
Pixels
class provides the more general form of the interface.
Obtain existing image pixels via
getPixels()
.   Create a new
pixel region using
setPixels().
In order to ensure that only the current generation of the image is
modified, the Image's
#modifyImage
modifyImage()
method
should be invoked to reduce the reference count on the underlying image
to one. If this is not done, then it is possible for a previous
generation of the image to be modified due to the use of reference
counting when copying or constructing an Image.
Depending on the capabilities of the operating system,   and the
relationship of the window to the image, the pixel cache may be a copy
of the pixels in the selected window, or it may be the actual image
pixels. In any case calling
syncPixels()
insures that the base
image is updated with the contents of the modified pixel cache. The
method
readPixels()
supports copying foreign pixel data formats
into the pixel cache according   to the
QuantumTypes
. The method
writePixels()
supports copying   the pixels in the cache to a foreign pixel
representation according to the  format specified by
QuantumTypes
.
The pixel region is effectively a small image in which   the pixels
may be accessed, addressed, and updated, as shown in the following
example:
Image image("cow.png");
// Ensure that there are no other references to this image.
image.modifyImage();
// Set the image type to TrueColor
DirectClass representation.
image.type(TrueColorType
);
// Request pixel region with size 60x40, and top origin at
20x30
int columns = 60;
PixelPacket *pixel_cache = image.getPixels(20,30,columns,40);
// Set pixel at column 5, and row 10 in the pixel cache to
red.
int column = 5;
int row = 10;
PixelPacket *pixel =
pixel_cache+row*columns*sizeof(PixelPacket)+column;
*pixel = Color("red");
// Save changes to underlying image
.
image.syncPixels();
// Save updated image to file.
image.write("horse.png");
The image cache supports the following methods:
Image Cache Methods
Method
Returns
Signature
Description
getConstPixels
const
PixelPacket.html
PixelPacket
*
const int x_, const int y_, const unsigned
int columns_,   const unsigned int rows_
Transfers pixels from the image to the pixel
cache as defined by the specified rectangular region.
The returned pointer remains valid until the next getPixel,
getConstPixels, or setPixels call and should never be deallocated by the
user.
getConstIndexes
const IndexPacket*
void
Returns a pointer to the Image pixel indexes
corresponding to a previous
getPixel,
getConstPixels, or setPixels call.
The
returned pointer remains valid until the next getPixel, getConstPixels,
or setPixels call and should never be deallocated by the user.
Only   valid for PseudoClass images or CMYKA images. The
pixel indexes represent   an array of type IndexPacket, with each entry
corresponding to an x,y pixel    position. For PseudoClass images, the
entry's value is the offset into the  colormap (see
#colorMap
colorMap
) for that pixel. For CMYKA images, the indexes are used to contain the
alpha channel.
getIndexes
IndexPacket*
void
Returns a pointer to the Image pixel indexes
corresponding to the pixel region requested by the last
#getConstPixels
getConstPixels
,
#getPixels
getPixels
, or
#setPixels
setPixels
call.
The
returned pointer remains valid until the next getPixel, getConstPixels,
or setPixels call and should never be deallocated by the user.
Only valid for PseudoClass images or
CMYKA images. The pixel indexes   represent an array of type
IndexPacket, with each entry corresponding to  a pixel x,y position. For
PseudoClass images, the entry's value is the offset   into the colormap
(see
#colorMap
colorMap
)  for that pixel. For CMYKA
images, the indexes are used to contain   the alpha channel.
getPixels
PixelPacket.html
PixelPacket
*
const int x_, const int y_, const unsigned
int columns_,   const unsigned int rows_
Transfers pixels from the image to the pixel
cache as defined by the specified rectangular region. Modified pixels
may be subsequently   transferred back to the image via syncPixels.
The returned pointer remains valid until the next getPixel,
getConstPixels, or setPixels call and should never be deallocated by the
user.
setPixels
PixelPacket.html
PixelPacket
*
const int x_, const int y_, const unsigned
int columns_,   const unsigned int rows_
Allocates a pixel cache region to store image
pixels as defined by the region rectangle.  This area is
subsequently transferred    from the pixel cache to the image via
syncPixels.
The returned pointer remains
valid until the next getPixel, getConstPixels, or setPixels call and
should never be deallocated by the user.
syncPixels
void
void
Transfers the image cache pixels to the image.
readPixels
void
Enumerations.html#QuantumTypes
QuantumTypes
quantum_, unsigned char *source_,
Transfers one or more pixel components from a
buffer or file into the image pixel cache of an image. ReadPixels is
typically used to support image decoders. The region transferred
corresponds to the region set by a preceding setPixels call.
writePixels
void
Enumerations.html#QuantumTypes
QuantumTypes
quantum_, unsigned char *destination_
Transfers one or more pixel components from
the image   pixel cache to a buffer or file. WritePixels is typically
used to  support   image encoders. The region transferred corresponds to
the region set by a preceding getPixels or getConstPixels call.
