MACROMEDIA FLASH 8-FLASH, Use Manual

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Publishing Flash documents 475
7. Select one of the following Palette Types to define the color palette for the PNG image:
Web 216 uses the standard 216-color, browser-safe palette to create the PNG image, for
good image quality and the fastest processing on the server.
Adaptive analyzes the colors in the image and creates a unique color table for the selected
PNG file. This option is best for systems showing thousands or millions of colors; it
creates the most accurate color for the image but results in a file size larger than a PNG
created with the web 216 palette.
Web Snap Adaptive is the same as the Adaptive palette option except that it converts
very similar colors to the web 216 color palette. The resulting color palette is optimized
for the image, but when possible, Flash uses colors from web 216. This produces better
colors for the image when the web 216 palette is active on a 256-color system.
To reduce the size of a PNG file with an adaptive palette, use the Max Colors option to
decrease the number of palette colors, as described in the next step.
Custom specifies a palette that you have optimized for the selected image. The custom
palette is processed at the same speed as the web 216 palette. To use this option, you
should know how to create and use custom palettes. To select a custom palette, click the
Ellipsis (...) button to the right of the Palette box at the bottom of the dialog box and
select a palette file. Flash supports palettes saved in the ACT format, exported by
Macromedia Fireworks and other leading graphics applications; for more information, see
“Importing and exporting color palettes” on page 126 .
8.
If you selected the Adaptive or Web Snap Adaptive palette in step 7, enter a value for Max
Colors to set the number of colors used in the PNG image. Selecting a smaller number of
colors can produce a smaller file but might degrade the colors in the image.
9. Select one of the following Filter options to select a line-by-line filtering method to make
the PNG file more compressible, and experiment with the different options for a particular
image:
None turns off filtering.
Sub transmits the difference between each byte and the value of the corresponding byte of
the prior pixel.
Up transmits the difference between each byte and the value of the corresponding byte of
the pixel immediately above.
Average uses the average of the two neighboring pixels (left and above) to predict the
value of a pixel.
Path
computes a simple linear function of the three neighboring pixels (left, above, upper
left), and then selects the neighboring pixel closest to the computed value as a predictor of
the color.