Mercurial > sdl-ios-xcode
comparison src/video/SDL_video.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 | f085091f74cd |
children | 64a60c5d502e |
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3332:da1cb54d74ef | 3333:b334b4f7dfa0 |
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2461 } | 2461 } |
2462 /* Clip srcrect by the same amount as dstrect was clipped */ | 2462 /* Clip srcrect by the same amount as dstrect was clipped */ |
2463 if (dstrect->w != real_dstrect.w) { | 2463 if (dstrect->w != real_dstrect.w) { |
2464 int deltax = (real_dstrect.x - dstrect->x); | 2464 int deltax = (real_dstrect.x - dstrect->x); |
2465 int deltaw = (real_dstrect.w - dstrect->w); | 2465 int deltaw = (real_dstrect.w - dstrect->w); |
2466 real_srcrect.x += (deltax * dstrect->w) / real_srcrect.w; | 2466 real_srcrect.x += (deltax * real_srcrect.w) / dstrect->w; |
2467 real_srcrect.w += (deltaw * dstrect->w) / real_srcrect.w; | 2467 real_srcrect.w += (deltaw * real_srcrect.w) / dstrect->w; |
2468 } | 2468 } |
2469 if (dstrect->h != real_dstrect.h) { | 2469 if (dstrect->h != real_dstrect.h) { |
2470 int deltay = (real_dstrect.y - dstrect->y); | 2470 int deltay = (real_dstrect.y - dstrect->y); |
2471 int deltah = (real_dstrect.h - dstrect->h); | 2471 int deltah = (real_dstrect.h - dstrect->h); |
2472 real_srcrect.y += (deltay * dstrect->h) / real_srcrect.h; | 2472 real_srcrect.y += (deltay * real_srcrect.h) / dstrect->h; |
2473 real_srcrect.h += (deltah * dstrect->h) / real_srcrect.h; | 2473 real_srcrect.h += (deltah * real_srcrect.h) / dstrect->h; |
2474 } | 2474 } |
2475 } | 2475 } |
2476 | 2476 |
2477 return renderer->RenderCopy(renderer, texture, &real_srcrect, | 2477 return renderer->RenderCopy(renderer, texture, &real_srcrect, |
2478 &real_dstrect); | 2478 &real_dstrect); |