Mercurial > sdl-ios-xcode
annotate docs/html/sdlsetgamma.html @ 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 | 355632dca928 |
| rev | line source |
|---|---|
| 0 | 1 <HTML |
| 2 ><HEAD | |
| 3 ><TITLE | |
| 4 >SDL_SetGamma</TITLE | |
| 5 ><META | |
| 6 NAME="GENERATOR" | |
|
55
55f1f1b3e27d
Added new docs for SDL 1.2.1
Sam Lantinga <slouken@lokigames.com>
parents:
0
diff
changeset
|
7 CONTENT="Modular DocBook HTML Stylesheet Version 1.64 |
| 0 | 8 "><LINK |
| 9 REL="HOME" | |
| 10 TITLE="SDL Library Documentation" | |
| 11 HREF="index.html"><LINK | |
| 12 REL="UP" | |
| 13 TITLE="Video" | |
| 14 HREF="video.html"><LINK | |
| 15 REL="PREVIOUS" | |
| 16 TITLE="SDL_SetPalette" | |
| 17 HREF="sdlsetpalette.html"><LINK | |
| 18 REL="NEXT" | |
| 19 TITLE="SDL_GetGammaRamp" | |
| 20 HREF="sdlgetgammaramp.html"></HEAD | |
| 21 ><BODY | |
| 22 CLASS="REFENTRY" | |
| 23 BGCOLOR="#FFF8DC" | |
| 24 TEXT="#000000" | |
| 25 LINK="#0000ee" | |
| 26 VLINK="#551a8b" | |
| 27 ALINK="#ff0000" | |
| 28 ><DIV | |
| 29 CLASS="NAVHEADER" | |
| 30 ><TABLE | |
| 31 WIDTH="100%" | |
| 32 BORDER="0" | |
| 33 CELLPADDING="0" | |
| 34 CELLSPACING="0" | |
| 35 ><TR | |
| 36 ><TH | |
| 37 COLSPAN="3" | |
| 38 ALIGN="center" | |
| 39 >SDL Library Documentation</TH | |
| 40 ></TR | |
| 41 ><TR | |
| 42 ><TD | |
| 43 WIDTH="10%" | |
| 44 ALIGN="left" | |
| 45 VALIGN="bottom" | |
| 46 ><A | |
| 47 HREF="sdlsetpalette.html" | |
| 48 >Prev</A | |
| 49 ></TD | |
| 50 ><TD | |
| 51 WIDTH="80%" | |
| 52 ALIGN="center" | |
| 53 VALIGN="bottom" | |
| 54 ></TD | |
| 55 ><TD | |
| 56 WIDTH="10%" | |
| 57 ALIGN="right" | |
| 58 VALIGN="bottom" | |
| 59 ><A | |
| 60 HREF="sdlgetgammaramp.html" | |
| 61 >Next</A | |
| 62 ></TD | |
| 63 ></TR | |
| 64 ></TABLE | |
| 65 ><HR | |
| 66 ALIGN="LEFT" | |
| 67 WIDTH="100%"></DIV | |
| 68 ><H1 | |
| 69 ><A | |
| 70 NAME="SDLSETGAMMA" | |
| 71 >SDL_SetGamma</A | |
| 72 ></H1 | |
| 73 ><DIV | |
| 74 CLASS="REFNAMEDIV" | |
| 75 ><A | |
|
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
76 NAME="AEN1185" |
| 0 | 77 ></A |
| 78 ><H2 | |
| 79 >Name</H2 | |
| 80 >SDL_SetGamma -- Sets the color gamma function for the display</DIV | |
| 81 ><DIV | |
| 82 CLASS="REFSYNOPSISDIV" | |
| 83 ><A | |
|
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
84 NAME="AEN1188" |
| 0 | 85 ></A |
| 86 ><H2 | |
| 87 >Synopsis</H2 | |
| 88 ><DIV | |
| 89 CLASS="FUNCSYNOPSIS" | |
| 90 ><A | |
|
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
91 NAME="AEN1189" |
| 0 | 92 ></A |
| 93 ><P | |
| 94 ></P | |
| 95 ><PRE | |
| 96 CLASS="FUNCSYNOPSISINFO" | |
| 97 >#include "SDL.h"</PRE | |
| 98 ><P | |
| 99 ><CODE | |
| 100 ><CODE | |
| 101 CLASS="FUNCDEF" | |
| 102 >int <B | |
| 103 CLASS="FSFUNC" | |
| 104 >SDL_SetGamma</B | |
| 105 ></CODE | |
| 106 >(float redgamma, float greengamma, float bluegamma);</CODE | |
| 107 ></P | |
| 108 ><P | |
| 109 ></P | |
| 110 ></DIV | |
| 111 ></DIV | |
| 112 ><DIV | |
| 113 CLASS="REFSECT1" | |
| 114 ><A | |
|
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
115 NAME="AEN1195" |
| 0 | 116 ></A |
| 117 ><H2 | |
| 118 >Description</H2 | |
| 119 ><P | |
| 120 >Sets the "gamma function" for the display of each color component. Gamma | |
| 121 controls the brightness/contrast of colors displayed on the screen. | |
| 122 A gamma value of <TT | |
| 123 CLASS="CONSTANT" | |
| 124 >1.0</TT | |
| 125 > is identity (i.e., no adjustment | |
| 126 is made).</P | |
| 127 ><P | |
| 128 >This function adjusts the gamma based on the "gamma function" parameter, | |
| 129 you can directly specify lookup tables for gamma adjustment with | |
| 130 <A | |
| 131 HREF="sdlsetgammaramp.html" | |
| 132 >SDL_SetGammaRamp</A | |
| 133 >.</P | |
| 134 ><P | |
| 135 >Not all display hardware is able to change gamma.</P | |
| 136 ></DIV | |
| 137 ><DIV | |
| 138 CLASS="REFSECT1" | |
| 139 ><A | |
|
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
140 NAME="AEN1202" |
| 0 | 141 ></A |
| 142 ><H2 | |
| 143 >Return Value</H2 | |
| 144 ><P | |
| 145 >Returns -1 on error (or if gamma adjustment is not supported).</P | |
| 146 ></DIV | |
| 147 ><DIV | |
| 148 CLASS="REFSECT1" | |
| 149 ><A | |
|
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
150 NAME="AEN1205" |
| 0 | 151 ></A |
| 152 ><H2 | |
| 153 >See Also</H2 | |
| 154 ><P | |
| 155 ><A | |
| 156 HREF="sdlgetgammaramp.html" | |
| 157 >SDL_GetGammaRamp</A | |
| 158 > | |
| 159 <A | |
| 160 HREF="sdlsetgammaramp.html" | |
| 161 >SDL_SetGammaRamp</A | |
| 162 ></P | |
| 163 ></DIV | |
| 164 ><DIV | |
| 165 CLASS="NAVFOOTER" | |
| 166 ><HR | |
| 167 ALIGN="LEFT" | |
| 168 WIDTH="100%"><TABLE | |
| 169 WIDTH="100%" | |
| 170 BORDER="0" | |
| 171 CELLPADDING="0" | |
| 172 CELLSPACING="0" | |
| 173 ><TR | |
| 174 ><TD | |
| 175 WIDTH="33%" | |
| 176 ALIGN="left" | |
| 177 VALIGN="top" | |
| 178 ><A | |
| 179 HREF="sdlsetpalette.html" | |
| 180 >Prev</A | |
| 181 ></TD | |
| 182 ><TD | |
| 183 WIDTH="34%" | |
| 184 ALIGN="center" | |
| 185 VALIGN="top" | |
| 186 ><A | |
| 187 HREF="index.html" | |
| 188 >Home</A | |
| 189 ></TD | |
| 190 ><TD | |
| 191 WIDTH="33%" | |
| 192 ALIGN="right" | |
| 193 VALIGN="top" | |
| 194 ><A | |
| 195 HREF="sdlgetgammaramp.html" | |
| 196 >Next</A | |
| 197 ></TD | |
| 198 ></TR | |
| 199 ><TR | |
| 200 ><TD | |
| 201 WIDTH="33%" | |
| 202 ALIGN="left" | |
| 203 VALIGN="top" | |
| 204 >SDL_SetPalette</TD | |
| 205 ><TD | |
| 206 WIDTH="34%" | |
| 207 ALIGN="center" | |
| 208 VALIGN="top" | |
| 209 ><A | |
| 210 HREF="video.html" | |
| 211 >Up</A | |
| 212 ></TD | |
| 213 ><TD | |
| 214 WIDTH="33%" | |
| 215 ALIGN="right" | |
| 216 VALIGN="top" | |
| 217 >SDL_GetGammaRamp</TD | |
| 218 ></TR | |
| 219 ></TABLE | |
| 220 ></DIV | |
| 221 ></BODY | |
| 222 ></HTML | |
| 223 > |