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view Xcode/TemplatesForXcodeTiger/SDL Application/main.c @ 3333:b334b4f7dfa0
[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 | 232e5e00e398 |
children |
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/* Simple program: Create a blank window, wait for keypress, quit. Please see the SDL documentation for details on using the SDL API: /Developer/Documentation/SDL/docs.html */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <math.h> #include "SDL.h" int main(int argc, char *argv[]) { Uint32 initflags = SDL_INIT_VIDEO; /* See documentation for details */ SDL_Surface *screen; Uint8 video_bpp = 0; Uint32 videoflags = SDL_SWSURFACE; int done; SDL_Event event; /* Initialize the SDL library */ if ( SDL_Init(initflags) < 0 ) { fprintf(stderr, "Couldn't initialize SDL: %s\n", SDL_GetError()); exit(1); } /* Set 640x480 video mode */ screen=SDL_SetVideoMode(640,480, video_bpp, videoflags); if (screen == NULL) { fprintf(stderr, "Couldn't set 640x480x%d video mode: %s\n", video_bpp, SDL_GetError()); SDL_Quit(); exit(2); } done = 0; while ( !done ) { /* Check for events */ while ( SDL_PollEvent(&event) ) { switch (event.type) { case SDL_MOUSEMOTION: break; case SDL_MOUSEBUTTONDOWN: break; case SDL_KEYDOWN: /* Any keypress quits the app... */ case SDL_QUIT: done = 1; break; default: break; } } } /* Clean up the SDL library */ SDL_Quit(); return(0); }