A tool to convert colored images into grayscale called "colorfilter", based on OpenCV

scripts/colorfilter/.gitignore

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+build
+*.jpg
+*.png

scripts/colorfilter/CMakeLists.txt

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+cmake_minimum_required (VERSION 3.8)
+
+project ("OI WIKI Color Filter")
+
+find_package(OpenCV REQUIRED)
+# opencv include path: /opt/opencv
+
+include_directories(${OpenCV_INCLUDE_DIRS})
+link_libraries(${OpenCV_LIBS})
+
+add_executable (colorfilter "main.cpp")

scripts/colorfilter/main.cpp

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+#include "opencv2/opencv.hpp"
+
+using namespace std;
+using namespace cv;
+
+int main(int argc, char *argv[]) {
+    int nx, ny;
+    Mat channels[3];
+
+    Mat img = imread(argv[1]);
+
+    Mat cell_small = imread("masksmall.bmp");
+    Mat cell_mid = imread("maskmid.bmp");
+    Mat cell_big = imread("maskbig.bmp");
+
+    Mat mask_small;
+    nx = img.size().width / cell_small.size().width + 1;
+    ny = img.size().height / cell_small.size().height + 1;
+    repeat(cell_small, ny, nx, mask_small);
+    mask_small = mask_small(Range(0, img.size().height), Range(0, img.size().width));
+
+
+    Mat mask_mid;
+    nx = img.size().width / cell_mid.size().width + 1;
+    ny = img.size().height / cell_mid.size().height + 1;
+    repeat(cell_mid, ny, nx, mask_mid);
+    mask_mid = mask_mid(Range(0, img.size().height), Range(0, img.size().width));
+
+    Mat mask_big;
+    nx = img.size().width / cell_big.size().width + 1;
+    ny = img.size().height / cell_big.size().height + 1;
+    repeat(cell_big, ny, nx, mask_big);
+    mask_big = mask_big(Range(0, img.size().height), Range(0, img.size().width));
+
+    Mat img_small = mask_small & img;
+    split(img_small, channels);
+    img_small = channels[0] + channels[1] + channels[2];
+
+    Mat img_mid = mask_mid & img;
+    split(img_mid, channels);
+    img_mid = channels[0] + channels[1] + channels[2];
+
+    Mat img_big = mask_big & img;
+    split(img_big, channels);
+    img_big = channels[0] + channels[1] + channels[2];
+
+    imwrite(string(argv[1]) + ".small.jpg", img_small);
+    imwrite(string(argv[1]) + ".mid.jpg", img_mid);
+    imwrite(string(argv[1]) + ".big.jpg", img_big);
+    return 0;
+}