Force Photoshop to include pure black at the beginning of the palette.
Editor: The Algorithm used by Photoshop 5.0.x to determine the best set of colors when converting a document to Indexed Color mode using the Adaptive palette has changed to allow for a more representative sampling of colors. One side-effect of this improvement is that Photoshop no longer guarantees that the generated palette will contain a pure white color and a pure black color. Images with palettes that do not contain pure white and pure black may not work properly in some applications.

When installed in Photoshops Plug-ins folder, the Force Black and White Extension Plug-in Forces Photoshop 5.0.x to include a pure black entry (0, 0, 0) at the beginning of the palette and a pure white (255, 255, 255) color at the end of the palette, whenever a document is converted into the Indexed Color mode using the Adaptive palette. Images converted in this fashion will work in the applications that require pure white and pure black palette entries, but the colors chosen will be slightly less optimal for the image since there are two less of them available.

To ensure this plug-in works, you must always select Best Color Matching (instead of FASTER) in the Index Color dialog Box when doing your Indexed Color mode conversion. Otherwise, the converted image may not use the newly added pure black and pure white palette entries. you can free download Force Black and White Extension Plug-in Force Black and Whit now.