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view docs/man3/SDL_Overlay.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_Overlay" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" .SH "NAME" SDL_Overlay\- YUV video overlay .SH "STRUCTURE DEFINITION" .PP .nf \f(CWtypedef struct{ Uint32 format; int w, h; int planes; Uint16 *pitches; Uint8 **pixels; Uint32 hw_overlay:1; } SDL_Overlay;\fR .fi .PP .SH "STRUCTURE DATA" .TP 20 \fBformat\fR Overlay format (see below) .TP 20 \fBw, h\fR Width and height of overlay .TP 20 \fBplanes\fR Number of planes in the overlay\&. Usually either 1 or 3 .TP 20 \fBpitches\fR An array of pitches, one for each plane\&. Pitch is the length of a row in bytes\&. .TP 20 \fBpixels\fR An array of pointers to teh data of each plane\&. The overlay should be locked before these pointers are used\&. .TP 20 \fBhw_overlay\fR This will be set to 1 if the overlay is hardware accelerated\&. .SH "DESCRIPTION" .PP A \fBSDL_Overlay\fR is similar to a \fI\fBSDL_Surface\fR\fR except it stores a YUV overlay\&. All the fields are read only, except for \fBpixels\fR which should be \fIlocked\fR before use\&. The \fBformat\fR field stores the format of the overlay which is one of the following: .PP .nf \f(CW#define SDL_YV12_OVERLAY 0x32315659 /* Planar mode: Y + V + U */ #define SDL_IYUV_OVERLAY 0x56555949 /* Planar mode: Y + U + V */ #define SDL_YUY2_OVERLAY 0x32595559 /* Packed mode: Y0+U0+Y1+V0 */ #define SDL_UYVY_OVERLAY 0x59565955 /* Packed mode: U0+Y0+V0+Y1 */ #define SDL_YVYU_OVERLAY 0x55595659 /* Packed mode: Y0+V0+Y1+U0 */\fR .fi .PP More information on YUV formats can be found at \fIhttp://www\&.webartz\&.com/fourcc/indexyuv\&.htm (link to URL http://www.webartz.com/fourcc/indexyuv.htm) \fR\&. .SH "SEE ALSO" .PP \fI\fBSDL_CreateYUVOverlay\fP\fR, \fI\fBSDL_LockYUVOverlay\fP\fR, \fI\fBSDL_UnlockYUVOverlay\fP\fR, \fI\fBSDL_FreeYUVOverlay\fP\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01