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Fix Upside Down Image #5

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Fix Upside Down Image #5

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1e1937c
Flip pixel data to fix shader/PNG coordinate system mismatch
acarlson99 May 28, 2025
7b22083
fix type error
acarlson99 May 28, 2025
ae78980
format
acarlson99 May 28, 2025
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12 changes: 10 additions & 2 deletions Main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,15 @@ emacs_value obGlslRun (emacs_env* env,
glReadBuffer(GL_COLOR_ATTACHMENT0);
glReadPixels(0,0,width,height,GL_RGBA,GL_UNSIGNED_BYTE,pixels.data());

auto surface = SDL_CreateRGBSurfaceFrom(pixels.data(), width, height,
// Flip the pixel data vertically
std::vector<uint8_t> flippedPixels(width * 4 * height);
for (int y = 0; y < height; ++y) {
memcpy(flippedPixels.data() + y * width * 4,
pixels.data() + (height - 1 - y) * width * 4,
width * 4);
}

auto surface = SDL_CreateRGBSurfaceFrom(flippedPixels.data(), width, height,
32/*depth*/, width * 4/*pitch*/,
0x000000ff, 0x0000ff00, 0x00ff0000, 0xff000000);
IMG_SavePNG(surface, outputPath.data());
Expand All @@ -92,7 +100,7 @@ int emacs_module_init (emacs_runtime *ert) noexcept {
emacs_env* env = ert->get_environment (ert);
try {
init();
glbinding::Binding::initialize(nullptr);
glbinding::Binding::initialize(false);
} catch (std::exception& e) {
reportError(env, e);
}
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