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[SDL] Bad math in SDL_RenderCopy Mason Wheeler to sdl When I tried to render an image using something other than NULL for srcrect, it got horribly distorted. I traced it down to the fact that the math in the rectangle adjustments performed just before the call to renderer->RenderCopy is written inside out. It should look like this: if (dstrect->w != real_dstrect.w) { int deltax = (dstrect->x - real_dstrect.x); int deltaw = (dstrect->w - real_dstrect.w); real_srcrect.x += (deltax * real_srcrect.w) / dstrect->w; real_srcrect.w += (deltaw * real_srcrect.w) / dstrect->w; } if (dstrect->h != real_dstrect.h) { int deltay = (dstrect->y - real_dstrect.y); int deltah = (dstrect->h - real_dstrect.h); real_srcrect.y += (deltay * real_srcrect.h) / dstrect->h; real_srcrect.h += (deltah * real_srcrect.h) / dstrect->h;
author Sam Lantinga <slouken@libsdl.org>
date Sat, 03 Oct 2009 16:23:16 +0000
parents c6a447c98584
children
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<!DOCTYPE HTML PUBLIC "-//Norman Walsh//DTD DocBook HTML 1.0//EN">
<HTML>
<HEAD><TITLE>Simple DirectMedia Layer Introduction</TITLE></HEAD>
<BODY BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000">
<DIV CLASS="NAVHEADER">
<HR ALIGN="LEFT" WIDTH="100%">
</DIV>
<DIV CLASS="PREFACE">
<H2><A NAME="AEN8">Simple DirectMedia Layer Introduction</A></H2>
<P>
This library is designed to make it easy to write games that run on many
different platforms using the various native high-performance media interfaces,
(for video, audio, etc) and presenting a single source-code level API to
your application.  This is a fairly low level API, but using this, completely
portable applications can be written with a great deal of flexibility.
</P><P>
An introduction to SDL can be found online at:
<A HREF="http://www.libsdl.org/intro.php" TARGET="_top">
         http://www.libsdl.org/intro.php</A>
</P><P>
Tutorials on a variety of topics can be found online at:
<A HREF="http://www.libsdl.org/tutorials.php" TARGET="_top">
         http://www.libsdl.org/tutorials.php</A>
</P><P>
Documentation in Wiki form can be found online at:
<A HREF="http://www.libsdl.org/cgi/docwiki.cgi/" TARGET="_top">
         http://www.libsdl.org/cgi/docwiki.cgi/</A>
</P><P>
Enjoy!
</P><P>
&nbsp;&nbsp;&nbsp; Sam Lantinga
<TT CLASS="EMAIL">&#60;<A HREF="mailto:slouken@libsdl.org"><A HREF="mailto:slouken@libsdl.org" TARGET="_top" >slouken@libsdl.org</A></A>&#62;</TT>
</P> <P>
<br><br><HR>
<H1>Table of Contents</H1>
<UL>
<LI><A HREF="html/index.html">Full Table of Contents</A></LI>
<LI><A HREF="html/guide.html">The SDL Guide</A></LI>
<LI><A HREF="html/reference.html">The SDL Reference</A></LI>
<UL>
<LI><A HREF="html/general.html">Initialization</A></LI>
<LI><A HREF="html/video.html">Video</A></LI>
<LI><A HREF="html/wm.html">Window Manager</A></LI>
<LI><A HREF="html/event.html">Event Handling</A></LI>
<LI><A HREF="html/joystick.html">Joystick</A></LI>
<LI><A HREF="html/audio.html">Audio</A></LI>
<LI><A HREF="html/cdrom.html">CDROM</A></LI>
<LI><A HREF="html/thread.html">Threads</A></LI>
<LI><A HREF="html/time.html">Timers</A></LI>
</UL>
</UL>
</DIV
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