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#4 2007-09-15 20:01:35
- kevin_karplus
- Scratcher
- Registered: 2007-04-27
- Posts: 1000+
Re: color change block
I think that the color effect just changes the hue and not the saturation or intensity, which means that there is no way to get a true negative.
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#5 2007-09-16 13:17:44
Re: color change block
A bit more information on color options. Scratch seems to use an indexed color pallet and, since it exports to .gif format, that means there will be a maximum of 256 colors. The color pallet used internally to the program does not have a code for either a black or a white - black must be obtained by setting brightness to -128 and white by setting transparency to 100% over a white background. A fairly good grey scale can be obtained by setting brightness to -128 and varying transparency, again over a white background. (Black, white and greys can, of course, also be set when drawing a sprite.) A color step of around 32 will give you a pretty good change in color, although that is only approximate - there don't seem to be true complements.
I've uploaded a short "Colors of GIF" program (http://scratch.mit.edu/projects/DrJim/36944) that I developed to assist in choosing colors in Scratch. For further general information on indexed color pallets, with specific application to .gif, see http://www.scantips.com/palettes.html .
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