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 dont make a selection, the entire image in edit
mode is affected. This command doesnt 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.