16.9. Viewing and Editing Images

Digikam comes with a comprehensive image viewing and editing suite consisting of various plug-ins. To enter Digikam's viewing and editing mode, double-click an image thumbnail. To use Digikam's plug-ins, you need to install the digikamplugins package.

Use View menu to zoom in and out of your image and to insert histograms. Using the Histogram option, you can judge the exposure of your image while viewing it.

Figure 16.5. Checking the Histogram

Checking the Histogram

Use the Image menu to edit the properties, comments and tags of your images and to apply basic effects or to insert text:

Apply Texture

Select the type of texture you want to apply to your image and determine how prominent this texture should be (Relief). Digikam applies the texture and saves the changes to the original copy of your image.

Add Border

Select the type of border. Depending on the type of border you have selected, choose one or two colors to be used for the border and set the width of the border around your image. Digikam creates the border and saves the changes to the original copy of your image.

Insert Text

Enter the text you want to superimpose on the image, choose font, font style and size. Select the text justification and decide whether the text should be rotated and to what degree. Add an optional border and semi-transparency. Digikam adds your text layer to the original image.

16.9.1. Fixing and Tweaking Your Images

Use the Fix menu to address a number of common defects related to digital imagery:

Colors

Tweaks various aspects of the image related to colors.

Blur/Sharpen

Tweaks the sharpness of your image or smoothens it.

Unsharp Mask

Enhances the sharpness of your image.

Refocus

Sharpens your image by trying to refocus it.

Red Eye Reduction

Reduces or eliminates red eyes caused by use of a flash.

Inpainting

Heals” defective areas of your image.

Hot Pixel Correction

Detects and erases defective pixels of your image caused by a defective pixels of your camera's sensor.

Restoration

Provides an all-inclusive treatment to images suffering from all sorts of digital defects such as noise and scratches.

Noise Reduction

Removes artifacts caused by dust etc. on your lens or your sensor. Compensates for pixel noise caused by high ISO settings of your digital camera and reduces noise and artifacts in low quality scans.

Lens Distortion Correction

Compensates barrel and pincushion distortion of your images caused by the use of strong wide-angle lenses or strong telephoto lenses.

Anti Vignetting

Compensates circular shades (vignettes) at the edges or in the center of your image that were caused by the use of strong wide-angle or telephoto lenses.

To illustrate the functionality of the Fix options, just have a look at the image inpainting option, for example. Assume, some dust or scratch on your lens ruined your otherwise perfect image. To remove this kind of artifact, proceed as follows:

  1. Open your image.

  2. Use the mouse cursor to select the area to which to apply the fix.

  3. Select Fix+Inpainting or press Shift-I.

  4. Determine the method to use to remove the artifact:

    • Choose one of the preset options (Remove Small Artifact, Remove Medium Artifact or Remove Large Artifact) and proceed with Step 6.

    • Set the filter parameters on your own. Proceed with Step 5.

  5. If you opted for not using any of the preset filters (in the Preset tab), open the Smoothing and Advanced Settings tabs and adjust the settings to your needs.

  6. Click OK to apply your settings and modify the image accordingly.

    [Tip]Creating and Reusing Your Own Filter Settings

    If you need to use the same set of settings more than once, e.g. if a scratch on the lense ruined an entire series of images, create your set of filter settings and save them for later use. Do so by clicking Save As and save them to a text file. For subsequent images you would just open the Image Inpainting dialog, click Load , select the text file and apply the filter settings with OK.

Figure 16.6. Using Image Inpainting to Remove Artifacts

Using Image Inpainting to Remove Artifacts

16.9.2. Applying Image Transformations

The Transform menu lets you apply a set of scaling and rotation operations to your image:

Rotate, Flip, Free Rotation

These options allow you to rotate your image to a certain degree. Rotate lets you rotate your images by multiples of 90 degrees, whereas Free Rotation lets you specify any angles you want.

Crop, Aspect Ratio Crop

These allow you to crop your image. Crop lets you do any rectangular selection on top of your image, whereas Aspect Ratio Crop allows you to crop the image following various sophisticated design principles.

Perspective Adjustment

Adjust the perspective of an image. For example, if you notice some odd angles in shots containing vertical or horizontal lines, use this tool to set them right. Grab any of the four handles to the corners of your image and move them as much as needed. Use the Crop tool to remove the resulting black edges of your image and to trim it down.

Shear

Shift one part of your image to one direction and the other to the opposite direction, either horizontally or vertically. Specify the angles for vertical and horizontal shear and use the Crop tool to trim the resulting image.

Resize, Blowup

Scale your image down or enlarge it. Resize offers a simple interface allowing you to manipulate your image size either by pixel or percentage. You may or you may not opt to keep the aspect ratio. Blowup lets you perform basically the same resizing operation on your image. In addition to a simple scaling operation you can enable filters to be applied on the scaled image to improve the quality of the resulting image. Whenever you need to print the final result, opt for Blowup instead for a simple Resize. You can save the filter settings to a text file and load and apply them to more images later on.

Assuming you have taken an image that is otherwise perfect, but you are not entirely satisfied with the composition yet or you need to crop your image in order to match a certain paper format for reproduction of this image. In this case, use Aspect Ratio Crop and proceed as follows:

  1. Open your image.

  2. Select Transform+Aspect Ratio Crop.

  3. Determine the orientation and aspect ratio to use:

    None

    Specify a free crop of the image using the X, Width, and Y, Height sliders.

    Custom

    Select a custom ration of width versus height instead of using one of the preset values.

    X:Y Ratio

    These ratios match most of the common paper sizes used to print photographs. Pick the one that suits your purpose best.

    Golden Ratio

    A ratio (1:1.618) that is traditionally used by artists and architects to create harmonious results.

    Use Max. Ratio to set the crop area to the maximum possible size the ratio you specified.

  4. After you determined the size of your crop selection, optionally apply compositional rules to it. The Composition Guide helps you to create a crop selection that results in a visually pleasing image. Dotted lines are displayed that guide you to a better composition of your image. The following options are available:

    • Rule of Thirds

    • Harmonious Triangles

    • Golden Mean

    • Golden Spiral

    • Golden Spiral Sections/Golden Rectangles

    • Golden Triangles

    • Golden Sections

    [Tip]For More Information

    For a comprehensive description of the options listed above, refer to http://docs.kde.org/development/en/extragear-graphics/digikam/using-kapp-imageeditor.html.

  5. Should the position of your crop not enforce the compositional rule you have selected, move it.

  6. Click OK to apply your crop selection and to trim your image.

Figure 16.7. Creating a Custom Crop Using Aspect Ratio Crop

Creating a Custom Crop Using Aspect Ratio Crop

16.9.3. Applying Filters and Effects

The Filters menu contains a selection of basic effects and filters which you can apply to your images to give them a more artistic or over-the-top look:

Black & White

Transform your colored image into a black and white one. Choose Neutral Black & White to get a simple grayscale image. Simulate the use of a color filter (green, orange, red and yellow) that accentuates areas of a certain color in the original image by selecting any of the Black & White with … Filter options. Simulate the tint effect of various chemicals of the dark room by selecting one of the Black & White with … Tone options.

Raindrops

Apply raindrop effects to your image. Determine the size and number of the drops and finally specify the degree of distortion caused by the drops (Fish eyes).

Infrared Film

Simulate the use of an IR filter to achieve a slightly surreal effect. The result will look strikingly different from any b/w image you know. Add additional film grain and tweak the sensibility (ISO) to achieve a more artistic feel.

Oil Paint

Simulate an oil painting. Determine the brush size and the degree of smoothing to be applied to your image.

Emboss

Pretend your image had been embossed to a sheet of paper. Choose an appropriate depth.

Solarize Image

Simulate an overexposure to sunlight.

Distortion Effects

Apply various strange distortion effects such as fish eyes to your image. Determine type, level and iteration.

Add Film Grain

Add film grain to your image to give it a rough look.

Blur Effects

Blur your image to simulate the image being out of focus or to mimic any kind of movement that was not there when you took the image.

Charcoal Drawing

Transform your image into a black and white charcoal drawing. Choose an appropriate pencil size and determine the degree of smoothing to be applied to the image.

Figure 16.8. Simulating IR Photography

Simulating IR Photography