Re: display_image()
- Posted by pwcroft at home.com Aug 05, 2001
- 465 views
I'm still a little lost. What is the easiest ways to use transparency? Best example? ----- Original Message ----- From: "Irv Mullins" <irvm at ellijay.com> To: "EUforum" <EUforum at topica.com> Subject: 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 > > > > >