Using the High Pass, Maximum, and Minimum filters This section describes how you can create selections in alpha chan- nels and resize bright areas in color channels. You can isolate areas in an image using the High Pass filter and Threshold command. You can use the Maximum and Minimum filters to spread color areas you might need to trap for commercial printing. Isolating areas using the High Pass filter The High Pass filter isolates high-contrast edges in an image by removing low-contrast detail. The filter makes pixels located in low- contrast areas gray. In color images, the High Pass filter outlines high-contrast edges in color. Otherwise, it outlines these edges in dark gray. To apply the High Pass filter 1 Select one or more paint objects to adjust all the images. You can select an area in one image in edit mode to adjust the selected area only. If you don’t make a selection, the entire image in edit mode is affected. This command doesn’t work with paint objects in Black & White mode, and Indexed mode. 2 Choose Image > Filter > Other > High Pass. 3 Enter a radius from 0.1 to 250.0 pixels. To retain more of the original image surrounding high-contrast edges, enter a high num- ber. If you enter a low number, the filter makes more of the image gray.
Canvas 8 Help: Image filters and effects (14 of 20)                                                 Page #720