&chalk; comes with a number of filters. These can be used to enhance or otherwise modify the image, either in whole or in part. Some filters are applied directly, others are customizable, meaning that you are presented with a dialog in which you can tune the result to your liking before the filter is applied. If a selection is active, a filter is applied on the selected part of the image. If no selection is active, the entire image is modified. This chapter describes the available filters in detail. To make comparing the filters easier, each filter has been applied to the same image and each description contains a comparison image, showing the result of applying the filter described. The original image (with thanks to the photographer, Christian Peper) is shown below at half the original size. The sample images demonstrating the results of applying the filters, with the original image at the left and the modified image at the right, are shown at 25% of the original size. Some filters yield reasonable results for most images. For other filters though, quite some tweaking needs to be done before the desired outcome is achieved. If a filter does not do what you want, it might need more or less customising. The examples in this chapter are exaggerated to give a good impression of the filters. You will usually want to have more gentle modifications. Tip: If you want to apply a filter to everything except a certain part of your image (for example, you want to desaturate your image except for the centre), select the part you do not want to apply the filter to, use the SelectInvert menu option, and then apply the filter. See the Dialogs for working with filters section for descriptions of the settings available for the customizable filters. The original image The original image The original image The Auto Contrast filter changes the contrast of your image to what should be the best settings. Usually this works out fine, but in some cases (for example photos taken under unusual lighting circumstances), the filter will not yield satisfying results. You can find the Auto Contrast filter in the Filter Adjust menu. This filter is not customizable. The image with the Auto Contrast filter applied to it The image with the Auto Contrast filter applied to it The image with the Auto Contrast filter applied to it You can use the Blur filter to blur your image (give it a fuzzy look). You can find the filter in the Filter Blur menu. See the section on the Blur dialog for more information on its settings. The image with the Blur filter applied to it The image with the Blur filter applied to it The image with the Blur filter applied to it With this filter, you can adjust the brightness and contrast of your image. You can find the filter in the Filter Adjust menu. See the section on the Brightness / Contrast dialog for more information on its settings. The image with the Brightness / Contrast filter applied to it The image with the Brightness / Contrast filter applied to it The image with the Brightness / Contrast filter applied to it The Bumpmap filter takes two layers and uses one of these to convert the other one so that it will give an illusion of depth. The object layer (the layer to be transformed) is the actual layer that should receive the three-dimensional looks. The bumpmap layer is a grayscale layer, which is read and used to determine the height for each point of the object layer. Alternatively, the same layer can be used as both object layer and bumpmap layer. You can find the filter in the Filter Map menu. See the section on the Bumpmap dialog for more information on its settings. The image with the Bumpmap filter applied to it The image with the Bumpmap filter applied to it The image with the Bumpmap filter applied to it With this filter, you can perform minor enhancements to your image, for example removing small scratches or adding a slight blur. The difference between our sample original image and the result of applying this filter with standard settings is virtually none. You can find the filter in the Filter Enhance menu. See the section on the Image Restoration dialog for more information on its settings. This filter allows you to change the looks of your image by increasing or decreasing the abundance of certain colors. You can find the filter in the Filter Adjust menu. See the section on the Color Adjustment dialog for more information on its settings. The image with the Color Adjustment filter applied to it The image with the Color Adjustment filter applied to it The image with the Color Adjustment filter applied to it This filter changes a color or color range in your image to become transparent, effectively clearing regions with those colors. You can find the filter in the Filter Colors menu. See the section on the Color to Alpha dialog for more information on its settings. The image with the Color to Alpha filter applied to it The image with the Color to Alpha filter applied to it The image with the Color to Alpha filter applied to it With this filter, you can re-color an image using the colors from another image. Each color in your current image will be replaced by the most alike color used in the other image. You can find the filter in the Filter Colors menu. See the section on the Color Transfer dialog for more information on its settings. The image with the Color Transfer filter applied to it The image with the Color Transfer filter applied to it The image with the Color Transfer filter applied to it This filter allows you to distort your image by setting a number of parameters. You can find the filter in the Filter Enhance menu. See the section on the Custom Convolution dialog for more information on its settings. The image with the Custom Convolution filter applied to it The image with the Custom Convolution filter applied to it The image with the Custom Convolution filter applied to it This filter converts your image to grayscale by setting the saturation of each pixel's color to zero. You can find the filter in the Filter Adjust menu. This filter is not customizable. The image with the Desaturate filter applied to it The image with the Desaturate filter applied to it The image with the Desaturate filter applied to it These filters try to detect edges (boundaries) in the picture and modify the image such that only these edges retain their respective colors, while the rest of the image is turned gray. Through the use of lighting the image will then get a three-dimensional look. There are four edge detection filters available. Each of these detects edges from a different side (possibly considering other parts of the image as being edges) and will therefore obtain a different resulting image. You can find the filters in the Filter Edge Detection menu. These filters are not customizable. The image with the Bottom Edge Detection filter applied to it The image with the Bottom Edge Detection filter applied to it The image with the Bottom Edge Detection filter applied to it Emboss filters work somewhat like edge detection filters, with the difference that embossed images are entirely gray. Areas in the picture are detected and are given a certain height level, which is made visible by using grayscale borders, making the image look like it is three-dimensional. You can find the filters in the Filter Emboss menu. Except for the Emboss with Variable Depth filter, these filters are not customizable. See the section on the Emboss dialog for more information on the settings of the Emboss with Variable Depth filter. The image with the Emboss in All Directions filter applied to it The image with the Emboss in All Directions filter applied to it The image with the Emboss in All Directions filter applied to it The image with the Emboss with Variable depth filter applied to it The image with the Emboss with Variable depth filter applied to it The image with the Emboss with Variable depth filter applied to it This filter makes the image a little fuzzy by blurring it in a pseudo-random way. A gaussian algorithm is used for finding the extent to which each part of the image should be blurred. You can find the filter in the Filter Blur menu. This filter is not customizable. The image with the Gaussian Blur filter applied to it The image with the Gaussian Blur filter applied to it The image with the Gaussian Blur filter applied to it With this filter, you can remove noise from your image. You can find the filter in the Filter Enhance menu. See the section on the Gaussian Noise Reduction dialog for more information on its settings. The image with the Gaussian Noise Reduction filter applied to it The image with the Gaussian Noise Reduction filter applied to it The image with the Gaussian Noise Reduction filter applied to it This filter inverts all colors. The Red, Green and Blue component of each pixel are taken and subtracted from 255. This means that red becomes cyan, green becomes purple, and blue becomes yellow. The resulting values form the new pixel color. You can find the filter in the Filter Adjust menu. This filter is not customizable. The image with the Invert filter applied to it The image with the Invert filter applied to it The image with the Invert filter applied to it This filter can fix distortions in your image resulting from for example pincushion lens effects, and modify some lighting. You can find the filter in the Filter Other menu. See the section on the Lens Correction dialog for more information on its settings. The image with the Lens Correction filter applied to it The image with the Lens Correction filter applied to it The image with the Lens Correction filter applied to it This filter gives each pixel in your image a new color: only the color channel that contributes the most to the color of a pixel is retained (except for gray pixels, which are kept gray). You can find the filter in the Filter Colors menu. This filter is not customizable. The image with the Maximize Channel filter applied to it The image with the Maximize Channel filter applied to it The image with the Maximize Channel filter applied to it This filter sharpens the image by changing the colors of neighboring pixels with approximately the same color, so that small differences are evened out. You can find the filter in the Filter Enhance menu. This filter is not customizable. The image with the Mean Removal filter applied to it The image with the Mean Removal filter applied to it The image with the Mean Removal filter applied to it This filter gives each pixel in your image a new color: the color channel that contributes the most to the color of a pixel is removed (except for gray pixels, which are kept gray). You can find the filter in the Filter Colors menu. This filter is not customizable. The image with the Minimize Channel filter applied to it The image with the Minimize Channel filter applied to it The image with the Minimize Channel filter applied to it An oilpaint effect is given to the image by creating patch-shaped areas in which the most important color is applied to the entire area. You can find the filter in the Filter Artistic menu. See the section on the Oilpaint dialog for more information on its settings. The image with the Oilpaint filter applied to it The image with the Oilpaint filter applied to it The image with the Oilpaint filter applied to it The image is pixelated by taking a square area and giving it the mean color value of the pixels it contains. You can find the filter in the Filter Artistic menu. See the section on the Pixelize dialog for more information on its settings. The image with the Pixelize filter applied to it The image with the Pixelize filter applied to it The image with the Pixelize filter applied to it This filter makes it look like raindrops have fallen on the image by distorting drop-shaped areas with a lens-like effect as one would see when looking at the image through a real raindrop. Some raindrops will have a fish-eye lens effect. You can find the filter in the Filter Artistic menu. See the section on the Raindrops dialog for more information on its settings. The image with the Raindrops filter applied to it The image with the Raindrops filter applied to it The image with the Raindrops filter applied to it With this filter, random noise can be added to your image. You can find the filter in the Filter Other menu. See the section on the Random Noise dialog for more information on its settings. The image with the Random Noise filter applied to it The image with the Random Noise filter applied to it The image with the Random Noise filter applied to it This filter distorts the image by interchanging pixels. You can find the filter in the Filter Other menu. See the section on the Random Pick dialog for more information on its settings. The image with the Random Pick filter applied to it The image with the Random Pick filter applied to it The image with the Random Pick filter applied to it This filter just rounds off the corners of the image. This is done by making the outside of the rounded corner transparent. You can find the filter in the Filter Map menu. See the section on the Round Corners dialog for more information on its settings. The image with the Round Corners filter applied to it The image with the Round Corners filter applied to it The image with the Round Corners filter applied to it This filter sharpens the image. You can find the filter in the Filter Enhance menu. This filter is not customizable. The image with the Sharpen filter applied to it The image with the Sharpen filter applied to it The image with the Sharpen filter applied to it The picture is reduced in size and repeated multiple times. You can find the filter in the Filter Map menu. See the section on the Small Tiles dialog for more information on its settings. The image with the Small Tiles filter applied to it The image with the Small Tiles filter applied to it The image with the Small Tiles filter applied to it This is a more enhanced edge detection filter. You can find the filter in the Filter Edge Detection menu. See the section on the Sobel dialog for more information on its settings. The image with the Sobel filter applied to it The image with the Sobel filter applied to it The image with the Sobel filter applied to it This filter sharpens part of your image. (The name unsharp is historical: parts would be masked off while the rest would be made less sharp.) You can find the filter in the Filter Enhance menu. See the section on the Unsharp Mask dialog for more information on its settings. The image with the Unsharp Mask filter applied to it The image with the Unsharp Mask filter applied to it The image with the Unsharp Mask filter applied to it This filter transforms your image into a wave shape. You can find the filter in the Filter Other menu. See the section on the Wave dialog for more information on its settings. The image with the Wave filter applied to it The image with the Wave filter applied to it The image with the Wave filter applied to it This filter reduces noise in the image by giving loose pixels a color close to the surrounding area. This causes small details to be lost, but can enhance the general view of the image when this is hampered by too many unnecessary details. You can find the filter in the Filter Enhance menu. See the section on the Wavelet Noise Reduction dialog for more information on its settings. The image with the Wavelet Noise Reduction filter applied to it The image with the Wavelet Noise Reduction filter applied to it The image with the Wavelet Noise Reduction filter applied to it