Re: display_image()
On Sunday 05 August 2001 05:52, pwcroft at home.com wrote:
> I'm using display_image() and I'm having the following problem. I use
> it once, to display the picture of a map, then again, to put a picture of a
> compass in the corner of the screen. But when I display the compass, the
> map vanishes, and I have a black screen, with the compass in the corner.
> Why is that? How do I fix it?
Are you trying to overlap the images? That won't work (without some extra
effort) because bitmaps don't support transparency.
If the images are NOT overlapping, you still have to arrive at a common
"palette" of colors. If you are using, for example, 256 colors, DOS keeps
an array of [0...255], and in each element of that array, stores the color
value for that color. If color[12] = 0, then color[12] would be black.
Your bitmaps have a similar array attached (the palette) which may
have some other value altogether stored in color[12]. Loading a new
bitmap can change all the colors of the bitmap which is already on display.
It's quite possible that your compass bitmap has only a few colors, with
zero stored in the rest of the color array. Therefor, most or all of the
colors in your map get changed to black when the compass is loaded.
The way to avoid this is to convert all your bitmaps to use the same,
common set of colors. Most good photo editing programs can do that,
programs like PaintShop Pro.
Regards,
Irv
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