nanogui: GrArea
Subject:
Re: GrArea
From:
Morten Rolland ####@####.####
Date:
1 Dec 2000 13:50:32 -0000
Message-Id: <3A27ADB5.CDB000B5@screenmedia.no>
####@####.#### wrote:
>
> what is the meaning of the variable psd->ncolors ?
>
Number of colors. It would be 16, 256, 65536 and huge for 4,8,16 and 24
bits respectively IIRC.
If you have an 8-bit display, and send color values larger than 255, then
the assert fails. I guess this is what goes wrong in your case.
> I read the source code the definition of MWPF_PIXELVAL is
> #define MWPF_RGB 0 /* pseudo, convert from packed 32 bit RGB*/
> #define MWPF_PIXELVAL 1 /* pseudo, no convert from packed PIXELVAL*/
> #define MWPF_PALETTE 2 /* pixel is packed 8 bits 1, 4 or 8 pal index*/
> #define MWPF_TRUECOLOR0888 3 /* pixel is packed 32 bits 8/8/8 truecolor*/
> #define MWPF_TRUECOLOR888 4 /* pixel is packed 24 bits 8/8/8 truecolor*/
> #define MWPF_TRUECOLOR565 5 /* pixel is packed 16 bits 5/6/5 truecolor*/
> #define MWPF_TRUECOLOR332 6 /* pixel is packed 8 bits 3/3/2 truecolor*/.
Notice that the packing that you use for the GrArea call should match
the number of bits per pixel of the display, unless MWPF_RGB is used.
In this case, I believe you can rely on a translation (possibly slow).
We (screen media) uses MWPF_TRUECOLOR565 to avoid translations, and send
only as much image bits as needed (16 bit color display).
I don't have any experience with GrReadArea.
Regards,
Morten Rolland
