CXT105@psuvm.psu.edu (Christopher Tate) (04/17/91)
I've got a bizarre little application with a bizarre little problem.
Basically what I'm doing is twiddling bits in an off-screen CGrafPort
directly and then blasting the result into a window with CopyBits. So
far, so good; the CopyBits works, etc. However, I've got a problem with
the Palette Manager.
I want to use (say) n shades of grey in my window; unfortunately, for rather
exotic reasons it is essential that these shades of grey be represented in
the offscreen CGrafPort by the pixel values 0 through n-1. I can't seem to
get the Palette Manger to do what I want it to. What I *want* is to set up
a palette with my desired colors in it, and have those colors appear when I
CopyBits the image into the window. What's happening is that I'm getting
the first n colors in the default system palette, not my greyscales.
If I use the Color Manager to SetEntries() on the first n colors, then I get
exactly what I want; unfortunately, I'm not sure how to go about saving and
restoring the original color map if I do that -- it gets *very* ugly on the
rest of the screen!
Do I have to (somehow) associate the palette I want to use with the CGrafPort
as well as with the Window? Do I have to muck about with CLUT's? How should
I go about resetting the original palette/CLUT/whatever when my application
quits? Etc....
-------
Christopher Tate |
| "An operating system, like a government,
cxt105@psuvm.psu.edu | performs no useful function by itself."
{...}!psuvax1!psuvm.bitnet!cxt105 |
cxt105@psuvm.bitnet |gerhard@cs.arizona.edu (Gerhard Mehldau) (04/17/91)
[Since this is a FAQ, I thought I'd post the solution.] > I've got a bizarre little application with a bizarre little problem. > Basically what I'm doing is twiddling bits in an off-screen CGrafPort > directly and then blasting the result into a window with CopyBits. So > far, so good; the CopyBits works, etc. However, I've got a problem with > the Palette Manager. > I want to use (say) n shades of grey in my window; unfortunately, for rather > exotic reasons it is essential that these shades of grey be represented in > the offscreen CGrafPort by the pixel values 0 through n-1. I can't seem to > get the Palette Manger to do what I want it to. What I *want* is to set up > a palette with my desired colors in it, and have those colors appear when I > CopyBits the image into the window. What's happening is that I'm getting > the first n colors in the default system palette, not my greyscales. Sounds all too familiar... What you need to do is create a 'clut' resource for your application, do CTabHandle gTable; gTable = GetCTable(kColorTable); SetPalette((WindowPtr)(-1), NewPalette((*gTable)->ctSize+1,gTable,pmTolerant+pmExplicit,0), TRUE); at the beginning of your program (before you create any windows) and then use "gTable" when you create your offscreen GWorlds -- and everything should work as you expect it. Note that instead of using the resource, you could also create the CLUT on the fly. > If I use the Color Manager to SetEntries() on the first n colors, then I get > exactly what I want; unfortunately, I'm not sure how to go about saving and > restoring the original color map if I do that -- it gets *very* ugly on the > rest of the screen! Don't do this -- you'll have to do it every time there is a context switch (i.e., when a DA is called, or when your application is put in the background), it looks _very_ bad, and it is a real hassle. > Do I have to (somehow) associate the palette I want to use with the CGrafPort > as well as with the Window? Do I have to muck about with CLUT's? How should > I go about resetting the original palette/CLUT/whatever when my application > quits? Etc.... Yes, and the easiest way to do it is to use the new GWorld calls in 32-bit QuickDraw -- all you need to do is pass in "gTable" when you create the offscreen GWorld, as in Rect rect; GWorldPtr pixmap; NewGWorld(&pixmap,gDepth,&rect,gTable,NULL,0L); This way you don't have to worry about saving/restoring CLUTs; 32-bit QuickDraw automagically takes care of it for you. Hope this helps. - Gerhard -- -> Gerhard Mehldau Dept. of Computer Science internet: gerhard@cs.arizona.edu University of Arizona uucp: {cmcl2,noao,uunet}!arizona!gerhard Tucson, AZ 85721, U.S.A. voice: +1 (602) 621-4632
CXT105@psuvm.psu.edu (Christopher Tate) (04/17/91)
The answer I got was quite useful, as far as it goes, but.... In article <2019@optima.cs.arizona.edu>, gerhard@cs.arizona.edu (Gerhard Mehldau) says: > [ ... ] the easiest way to do it is to use the new GWorld calls in 32-bit >QuickDraw -- all you need to do is pass in "gTable" when you create the >offscreen GWorld, as in > > Rect rect; > GWorldPtr pixmap; > > NewGWorld(&pixmap,gDepth,&rect,gTable,NULL,0L); > >This way you don't have to worry about saving/restoring CLUTs; 32-bit >QuickDraw >automagically takes care of it for you. Unfortunately, I can't find documentation for the 32-bit Quickdraw calls *anywhere*. Is this yet another truly useful facility which is only documented in Inside Macintosh VI? The only things I've been able to scrounge up are some not-very-useful files under /pub/dts/mac/docs or some such at apple.apple.com, and the tech note called "So many bitmaps, so little time," which doesn't tell me what I need to know. Where are the 32-bit Quickdraw calls documented, and how can I get hold of them? I'm getting pretty sick of all this "only available on the developer CD's" stuff.... ------- Christopher Tate | | "Idle lawyers tend to become politicians, cxt105@psuvm.psu.edu | so there is a certain social value {...}!psuvax1!psuvm.bitnet!cxt105 | in keeping them busy." cxt105@psuvm.bitnet |