Implement contrast fix

stackercpp.cpp

@@ -61,6 +61,33 @@ Stacker::add_frame(unsigned char *data, int width, int height)
 Mat
 Stacker::postprocess_mat(Mat input)
 {
+    stopwatch_start();
+    Mat blur;
+    GaussianBlur(input, blur, Size(0, 0), 1.8);
+    std::vector<cv::Mat> rgb_planes(3);
+    cv::split(blur, rgb_planes);
+    double min_r, max_r, min_g, max_g, min_b, max_b;
+    minMaxIdx(rgb_planes[0], &min_b, &max_b);
+    minMaxIdx(rgb_planes[1], &min_g, &max_g);
+    minMaxIdx(rgb_planes[2], &min_r, &max_r);
+    input = input - Scalar(min_b + 5, min_g + 5, min_r + 5);
+    double scale_r, scale_g, scale_b;
+    scale_r = 255 / (max_r - min_r + 5);
+    scale_g = (255 / (max_g - min_g + 5));
+    scale_b = 255 / (max_b - min_b + 5);
+    multiply(input, Scalar(scale_b, scale_g, scale_r), input);
+    stopwatch_mark("levels");
+
+    stopwatch_start();
+    float gamma = 1 / 0.9;
+    Mat table(1, 256, CV_8U);
+    uchar *p = table.ptr();
+    for (int i = 0; i < 256; ++i) {
+        p[i] = (uchar) (pow(i / 255.0, gamma) * 255);
+    }
+    LUT(input, table, input);
+    stopwatch_mark("gamma");
+
     stopwatch_start();
     Mat sharpened;
     GaussianBlur(input, sharpened, Size(0, 0), 1.7);
@@ -74,10 +101,11 @@ Stacker::postprocess_mat(Mat input)
     cv::split(lab, lab_planes);
     stopwatch_mark("to Lab");
 
-    /*
+    /* Disabled CLAHE local contrast, it's a bit to overpronounced and doesn't
+     * seem really necessary at this point
     stopwatch_start();
     cv::Ptr<cv::CLAHE> clahe = cv::createCLAHE();
-    clahe->setClipLimit(2);
+    clahe->setClipLimit(1);
     clahe->setTilesGridSize(Size(8, 8));
     cv::Mat dst;
     clahe->apply(lab_planes[0], dst);