640 Corel PaintShop Pro X7 User Guide
• Error Diffusion — replaces the original color of a pixel with the
most similar color in the palette, but spreads the discrepancy
between the original and new colors to the surrounding pixels. As
it replaces a color (working from the top left to the bottom right
of the image), it adds the “error,” or discrepancy, to the next pixel,
before selecting the most similar color. This method produces a
natural-looking image and often works well for photos or complex
graphics. With the Error Diffusion method, you select the Floyd-
Steinberg, Burkes, or Stucki algorithm for the dithering pattern.
• Ordered Dither — adjusts adjacent pixels so that two colors give
the illusion of a third color and intermingles pixels to produce
patterns based on a known palette. You can use this method to
give the image the appearance of containing more colors than it
actually does. Images may appear to be composed of cross-
hatches and dots and may have distinct light and dark areas.
When you decrease an image’s color depth, don’t be intimidated by
the mathematical algorithms that make up the color reduction
methods and the palette options. It’s recommended that you start
with the default settings. If you like the result, try out several other
combinations of settings. It take can take some experimentation to
find the right options.
Understanding palette options
When you decrease the color depth of an image, you must select a
palette option. Depending on the color depth you select, two or three
of these methods are available:
Optimized Median Cut — measures and ranks each color by how
frequently it occurs in the image, then uses the most frequently
occurring colors to determine the new palette. Even if your image
contains fewer colors than the palette that is generated, this method
may not represent each color exactly. The method, therefore, is not as
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