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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 | 55f1f1b3e27d |
children | 355632dca928 |
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<HTML ><HEAD ><TITLE >Examples</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.64 "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="SDL Guide" HREF="guide.html"><LINK REL="PREVIOUS" TITLE="Handling the Keyboard" HREF="guideinputkeyboard.html"><LINK REL="NEXT" TITLE="Event Examples" HREF="guideeventexamples.html"></HEAD ><BODY CLASS="CHAPTER" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >SDL Library Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="guideinputkeyboard.html" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="guideeventexamples.html" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="CHAPTER" ><H1 ><A NAME="GUIDEEXAMPLES" >Chapter 4. Examples</A ></H1 ><DIV CLASS="TOC" ><DL ><DT ><B >Table of Contents</B ></DT ><DT ><A HREF="guideexamples.html#AEN369" >Introduction</A ></DT ><DT ><A HREF="guideeventexamples.html" >Event Examples</A ></DT ><DT ><A HREF="guideaudioexamples.html" >Audio Examples</A ></DT ><DT ><A HREF="guidecdromexamples.html" >CDROM Examples</A ></DT ><DT ><A HREF="guidetimeexamples.html" >Time Examples</A ></DT ></DL ></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN369" >Introduction</A ></H1 ><P >For the moment these examples are taken directly from the old SDL documentation. By the 1.2 release these examples should hopefully deal with most common SDL programming problems.</P ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="guideinputkeyboard.html" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="guideeventexamples.html" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Handling the Keyboard</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="guide.html" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Event Examples</TD ></TR ></TABLE ></DIV ></BODY ></HTML >