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8b17e2ef62
Before this commit loadPNG() could return any surface format and the caller was responsible for converting it to the desired format. However, in practice all callers want a surface with an alpha channel and SDL only supports that with 32bpp surfaces, so RGBA or a permutation thereof. So I changed the contract for loadPNG() so it is required to return an RGBA surface, and removed the conversion code in the callers. The next step is to replace IMG_Load() by a function that calls libpng directly and loads a fixed 32bpp pixel format. That way, we can drop the SDL_image dependency and avoid unnecessary pixel format conversions.
37 lines
1.0 KiB
C++
37 lines
1.0 KiB
C++
#include "imageio.h"
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#include <SDL_image.h>
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SDL_Surface *loadPNG(const std::string &path) {
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// Load PNG file into an SDL surface.
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SDL_Surface *surface = IMG_Load(path.c_str());
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if (!surface) {
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return NULL;
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}
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// Make sure we have a surface that can be blitted using alpha blending.
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if (surface->format->BytesPerPixel == 4) {
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SDL_SetAlpha(surface, SDL_SRCALPHA, 255);
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return surface;
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} else {
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SDL_PixelFormat format32;
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memset(&format32, 0, sizeof(format32));
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format32.BitsPerPixel = 32;
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format32.BytesPerPixel = 4;
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format32.Rmask =
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SDL_BYTEORDER == SDL_BIG_ENDIAN ? 0x00FF0000 : 0x000000FF;
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format32.Gmask = 0x0000FF00;
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format32.Bmask =
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SDL_BYTEORDER == SDL_BIG_ENDIAN ? 0x000000FF : 0x00FF0000;
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format32.Amask = 0xFF000000;
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format32.Rshift = SDL_BYTEORDER == SDL_BIG_ENDIAN ? 16 : 0;
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format32.Gshift = 8;
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format32.Bshift = SDL_BYTEORDER == SDL_BIG_ENDIAN ? 0 : 16;
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format32.Ashift = 24;
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SDL_Surface *surface32 =
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SDL_ConvertSurface(surface, &format32, SDL_SRCALPHA);
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SDL_FreeSurface(surface);
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return surface32;
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}
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}
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