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Flips a surface in SDL
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SDL_Surface* flip_vertical(SDL_Surface* sfc) { | |
SDL_Surface* result = SDL_CreateRGBSurface(sfc->flags, sfc->w, sfc->h, | |
sfc->format->BytesPerPixel * 8, sfc->format->Rmask, sfc->format->Gmask, | |
sfc->format->Bmask, sfc->format->Amask); | |
const auto pitch = sfc->pitch; | |
const auto pxlength = pitch*(sfc->h - 1); | |
auto pixels = static_cast<unsigned char*>(sfc->pixels) + pxlength; | |
auto rpixels = static_cast<unsigned char*>(result->pixels) ; | |
for(auto line = 0; line < sfc->h; ++line) { | |
memcpy(rpixels,pixels,pitch); | |
pixels -= pitch; | |
rpixels += pitch; | |
} | |
return result; | |
} |
Thanks - I updated line 6
:-)
How would I approach doing this operation but for horizontal flipping
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Almost perfect.
pixels needs to change to start at the begining of the last line of pixels, not one line beyond the last pixel.
changing line 6 to:
const auto pxlength = pitch*(sfc->h - 1);
works for me