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| #define STB_IMAGE_IMPLEMENTATION | |
| #define STB_IMAGE_WRITE_IMPLEMENTATION | |
| #define _CRT_SECURE_NO_WARNINGS 1 | |
| #include <stb_image.h> | |
| #include <stb_image_write.h> | |
| #include <vector> | |
| #include <chrono> | |
| #include <iostream> | |
| void Rotate2701(const unsigned char* input, | |
| int width, int height, unsigned char* output) | |
| { | |
| const std::uint32_t* inputPixels = reinterpret_cast<const std::uint32_t*>(input); | |
| std::uint32_t* outputPixels = reinterpret_cast<std::uint32_t*>(output); | |
| const std::uint32_t kBlockPixelSize = 4; | |
| const std::uint32_t rowBlockCount = width / kBlockPixelSize; | |
| const std::uint32_t colBlockCount = height / kBlockPixelSize; | |
| const auto transpose = [&](int x, int y) { | |
| outputPixels[y + (width - x - 1) * height] = inputPixels[y * width + x]; | |
| }; | |
| //transpose blocks first | |
| for (int i = 0; i < height - kBlockPixelSize; i += kBlockPixelSize) | |
| { | |
| for (int j = 0; j < width - kBlockPixelSize; j += kBlockPixelSize) | |
| { | |
| for(int k = 0; k < kBlockPixelSize; ++k) | |
| { | |
| int y = i + k; | |
| for (int m = 0; m < kBlockPixelSize; ++m) | |
| { | |
| int x = j + m; | |
| transpose(x, y); | |
| } | |
| } | |
| } | |
| } | |
| //pixels left | |
| int leftXStart = static_cast<int>(rowBlockCount * kBlockPixelSize); | |
| int leftYStart = static_cast<int>(colBlockCount * kBlockPixelSize); | |
| for (int i = leftYStart; i < height; ++i) | |
| { | |
| for (int j = leftXStart; j < width; ++j) | |
| { | |
| transpose(j, i); | |
| } | |
| } | |
| } | |
| void Rotate2702(const unsigned char* input, | |
| int width, int height, unsigned char* output) | |
| { | |
| const std::uint32_t* inputPixels = reinterpret_cast<const std::uint32_t*>(input); | |
| std::uint32_t* outputPixels = reinterpret_cast<std::uint32_t*>(output); | |
| const auto transpose = [&](int x, int y) { | |
| outputPixels[y + (width - x - 1) * height] = inputPixels[y * width + x]; | |
| }; | |
| for (int i = 0; i < height; ++i) | |
| { | |
| for (int j = 0; j < width; ++j) | |
| { | |
| transpose(j, i); | |
| } | |
| } | |
| } | |
| int main() | |
| { | |
| const char* const inputPath = R"()"; | |
| const char* const destPath = R"(.\foo.png)"; | |
| int x, y, channels; | |
| unsigned char* inputPixels = stbi_load(inputPath, | |
| &x, &y, &channels, 4); | |
| std::vector<unsigned char> outputPixels(static_cast<std::size_t>(x * y * 4)); | |
| auto startTime = std::chrono::high_resolution_clock::now(); | |
| Rotate2702(inputPixels, x, y, outputPixels.data()); | |
| auto endTime = std::chrono::high_resolution_clock::now(); | |
| auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(endTime - startTime).count(); | |
| std::cout << "Time elapsed: " << duration << ".\n"; | |
| stbi_image_free(inputPixels); | |
| stbi_write_png(destPath, y, x, 4, outputPixels.data(), y * 4); | |
| } |
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