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view docs/man3/SDL_FillRect.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_FillRect" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" .SH "NAME" SDL_FillRect\- This function performs a fast fill of the given rectangle with some color .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" .sp \fBint \fBSDL_FillRect\fP\fR(\fBSDL_Surface *dst, SDL_Rect *dstrect, Uint32 color\fR); .SH "DESCRIPTION" .PP This function performs a fast fill of the given rectangle with \fBcolor\fR\&. If \fBdstrect\fR is \fBNULL\fP, the whole surface will be filled with \fBcolor\fR\&. .PP The color should be a pixel of the format used by the surface, and can be generated by the \fISDL_MapRGB\fR or \fISDL_MapRGBA\fR functions\&. If the color value contains an alpha value then the destination is simply "filled" with that alpha information, no blending takes place\&. .PP If there is a clip rectangle set on the destination (set via \fISDL_SetClipRect\fR) then this function will clip based on the intersection of the clip rectangle and the \fBdstrect\fR rectangle and the dstrect rectangle will be modified to represent the area actually filled\&. .SH "RETURN VALUE" .PP This function returns \fB0\fR on success, or \fB-1\fR on error\&. .SH "SEE ALSO" .PP \fI\fBSDL_MapRGB\fP\fR, \fI\fBSDL_MapRGBA\fP\fR, \fI\fBSDL_BlitSurface\fP\fR, \fI\fBSDL_Rect\fR\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01