24bpp + palette

[wsu-cb]

CPlayBoardView::OnEditBoardToFile() has a declaration
CDib dib(bmap, GetAppPalette(), uint16_t(24));
in it. What does it mean for a 24bpp bitmap (or DIB) to also have a palette?

[DLLarson]

That code is for exporting a bitmap of the board. It's using the usual 8 bit per channel format for a total of 24 bits per pixel.

When a palette based bitmap is exported to 24bpp the conversion should just look up each pixel in the palette bitmap in the palette and export that value for that pixel. The output file should NOT contain a palette as it wouldn't make sense. I have heard of (back in the old days) of supporting larger (64k palette tables) but I don't think they went anywhere.

The whole reason CB even supported pixels is that when it was first created 24 bit graphics were not common at all. Hardware that provided expanded color support used 8 bit pixels with palette look up. Palettes can be a total PITA when mapping colors and matching colors so I jumped at the chance when 16bbp support became common.

Plus getting decent bitmap images from scans required that dithering techniques be used. 16 bits per pixel (in 565 format) gave decent results while not totally growing the size of bitmaps stored in the gameboxes plus the palette isn't used. Basically it just doubled their raw size.

-Dale