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Problem Getting PICTS to Display in Correct Colors

Q: I'm having problems getting PICTs to display with the colors I want. I'm converting GIF files to PICTs by drawing the GIF into an offscreen GWorld. I'm using the Palette Manager to set up the colors, but there's no way to associate a palette with an offscreen PixMap. After I'm done drawing the GIF to a PixMap, I open the picture with the offscreen PixMap as the current port and use CopyBits to copy the PixMap onto itself, creating the picture. The problem is that if I use srcCopy, the colors are incorrect in the PICT when opened with TeachText (and other applications). But if I use ditherCopy the colors are saved correctly. I can use srcCopy if I do a CopyBits to/from a "color" window with the window's palette changed to my color palette. Is there a way to assign a palette to use for OpenPicture and still use CopyBits from an offscreen bitmap with srcCopy?

A: You can associate a palette with a GWorld, but it won't solve your problem: since a GWorld never becomes "active," the associated device's colors are never changed to match the palette. The solution is to use a custom color table with the GWorld. And you can easily use Palette Manager routines to convert your palette to a color table.

Use the Palette2CTab routine to perform the conversion. Palette2CTab takes a PaletteHandle and a CTabHandle and copies all the colors from the palette into the color table, resizing the color table as necessary. If the palette handle is nil, no change takes place.

Now you have a color table that you can associate with your GWorld. You can pass it to NewGWorld when you create your GWorld initially; the fourth parameter is a handle to a color table. You need to explicitly set the depth in this call for best results. (If you pass nil for the depth, the color table parameter will be ignored and the depth of the GWorld will be set to match the deepest device that intersects the GWorld's boundary rectangle.) The other possibility is to associate the color table with an existing GWorld using UpdateGWorld.

[Sep 15 1995]

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