光棱坦克OpenCV提取法

光棱坦克OpenCV提取法.cpp

// SPDX-License-Identifier: MIT

#include <algorithm>
#include <opencv2/opencv.hpp>

int main(int argc, char **argv) {
	cv::Mat img = cv::imread(argv[1]);
	cv::Mat img_out(img.rows, img.cols, img.type());

	const auto maxrow = img.rows, maxcol = img.cols;
	// Extract pixels
	for (int r = 0; r < maxrow; r++) {
		for (int c = (r % 2 ? 1 : 0); c < maxcol; c += 2) {
			const auto offset = 3 * (r * maxcol + c);
			memcpy(img_out.data + offset, img.data + offset, 3);
		}
	}
	// Median filtering
	int r_max = 0, g_max = 0, b_max = 0;
	for (int r = 0; r < maxrow; r++) {
		for (int c = (r % 2 ? 0 : 1); c < img.cols; c += 2) {
			// Pixel color getter with bound check
			auto getSafe = [&](int row, int col, int offset) {
				if (col > maxcol) {
					col = maxcol - 1;
					row--;
				} else if (col < 0) {
					col = 0;
					row++;
				}

				if (row > maxrow) {
					row = maxrow - 1;
					col--;
				} else if (row < 0) {
					row = 0;
					col++;
				}

				return img_out.data[(row * maxcol + col) * 3 + offset];
			};
			const auto offset = 3 * (r * maxcol + c);
			img_out.data[offset] = (getSafe(r, c - 1, 0) + getSafe(r, c + 1, 0) +
								    getSafe(r - 1, c, 0) + getSafe(r + 1, c, 0)) / 4;
			img_out.data[offset + 1] = (getSafe(r, c - 1, 1) + getSafe(r, c + 1, 1) +
								        getSafe(r - 1, c, 1) + getSafe(r + 1, c, 1)) / 4;
			img_out.data[offset + 2] = (getSafe(r, c - 1, 2) + getSafe(r, c + 1, 2) +
								        getSafe(r - 1, c, 2) + getSafe(r + 1, c, 2)) / 4;
			b_max = std::max(b_max, int(img_out.data[offset]));
			g_max = std::max(g_max, int(img_out.data[offset + 1]));
			r_max = std::max(r_max, int(img_out.data[offset + 2]));
		}
	}
	// Auto exposure
	float r_coeff = 255.0f / r_max, g_coeff = 255.0f / g_max, b_coeff = 255.0f / b_max;
	for (int r = 0; r < maxrow; r++) {
		for (int c = 0; c < maxcol; c++) {
			const auto offset = 3 * (r * maxcol + c);
			img_out.data[offset] *= b_coeff;
			img_out.data[offset + 1] *= g_coeff;
			img_out.data[offset + 2] *= r_coeff;
		}
	}

	cv::imwrite(cv::String(argv[1]) + "out.png", img_out);
}