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view docs/man3/SDL_CreateRGBSurfaceFrom.3 @ 688:c0522010bb6d
Date: Tue, 12 Aug 2003 14:26:19 +0200 (MEST)
From: "Mattias Engdeg?rd"
Subject: bug in SDL_GetRGB/GetRGBA
There's an embarrassing bug in GetRGB/GetRGBA which apparently has been there
for years. It incorrectly converts colours with < 8 bits/channel.
It came to my attention today in #sdl.
What it does now is (for each channel):
rv = (pixel & fmt->Rmask) >> fmt->Rshift;
*r = (rv << fmt->Rloss) + (rv >> (8 - fmt->Rloss));
which is wrong; the last line should be
*r = (rv << fmt->Rloss) + (rv >> (8 - (fmt->Rloss << 1)));
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Tue, 12 Aug 2003 15:17:20 +0000 |
| parents | e5bc29de3f0a |
| children | 546f7c1eb755 |
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.TH "SDL_CreateRGBSurfaceFrom" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" .SH "NAME" SDL_CreateRGBSurfaceFrom\- Create an SDL_Surface from pixel data .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" .sp \fBSDL_Surface *\fBSDL_CreateRGBSurfaceFrom\fP\fR(\fBvoid *pixels, int width, int height, int depth, int pitch, Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask\fR); .SH "DESCRIPTION" .PP Creates an SDL_Surface from the provided pixel data\&. .PP The data stored in \fBpixels\fR is assumed to be of the \fBdepth\fR specified in the parameter list\&. The pixel data is not copied into the \fBSDL_Surface\fR structure so it should not be freed until the surface has been freed with a called to \fISDL_FreeSurface\fR\&. \fBpitch\fR is the length of each scanline in bytes\&. .PP See \fI\fBSDL_CreateRGBSurface\fP\fR for a more detailed description of the other parameters\&. .SH "RETURN VALUE" .PP Returns the created surface, or \fBNULL\fR upon error\&. .SH "SEE ALSO" .PP \fI\fBSDL_CreateRGBSurface\fP\fR, \fI\fBSDL_FreeSurface\fP\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01