Make clamp a static inline function.

At best, this is two instructions on x86-64, so the cost of the function
call is significant. It's a templated standard library function in
C++17, so make it match the standard interface.

Also remove atan2deg, which should also be static inline but isn't used.

About 1% speedup.

tools/ld-comb-ntsc/comb.cpp

@@ -274,8 +274,8 @@ void Comb::split2D(FrameBuffer *frameBuffer)
                 kn /= 2;
 
                 qreal p_2drange = 45 * irescale;
-                kp = clamp(1 - (kp / p_2drange), 0, 1);
-                kn = clamp(1 - (kn / p_2drange), 0, 1);
+                kp = clamp(1 - (kp / p_2drange), 0.0, 1.0);
+                kn = clamp(1 - (kn / p_2drange), 0.0, 1.0);
 
                 qreal sc = 1.0;
 
@@ -563,17 +563,3 @@ void Comb::adjustY(FrameBuffer *frameBuffer, YiqBuffer &yiqBuffer)
         }
     }
 }
-
-qreal Comb::clamp(qreal v, qreal low, qreal high)
-{
-        if (v < low) return low;
-        else if (v > high) return high;
-        else return v;
-}
-
-qreal Comb::atan2deg(qreal y, qreal x)
-{
-    qreal rv = static_cast<double>(atan2(static_cast<long double>(y), x) * (180 / M_PIl));
-    if (rv < 0) rv += 360;
-    return rv;
-}

tools/ld-comb-ntsc/comb.h

@@ -133,9 +133,6 @@ class Comb
     QByteArray yiqToRgbFrame(YiqBuffer yiqBuffer, qreal burstLevel);
     void overlayOpticalFlowMap(FrameBuffer frameBuffer, QByteArray &rgbOutputFrame);
     void adjustY(FrameBuffer *frameBuffer, YiqBuffer &yiqBuffer);
-
-    qreal clamp(qreal v, qreal low, qreal high);
-    qreal atan2deg(qreal y, qreal x);
 };
 
 #endif // COMB_H

tools/ld-comb-ntsc/opticalflow.cpp

@@ -61,7 +61,7 @@ void OpticalFlow::denseOpticalFlow(YiqBuffer yiqBuffer, QVector<qreal> &kValues)
                 // in the X direction than the y
                 qreal velocity = calculateDistance(static_cast<qreal>(flowatxy.y), static_cast<qreal>(flowatxy.x) * 2);
 
-                kValues[(910 * y) + x] = clamp(velocity, 0, 1);
+                kValues[(910 * y) + x] = clamp(velocity, 0.0, 1.0);
             }
         }
     } else kValues.fill(1);
@@ -89,14 +89,6 @@ cv::Mat OpticalFlow::convertYtoMat(YiqBuffer yiqBuffer)
     return cv::Mat(525, 910, CV_16UC1, frame);
 }
 
-// Method to clamp a value within a low and high range
-qreal OpticalFlow::clamp(qreal v, qreal low, qreal high)
-{
-        if (v < low) return low;
-        else if (v > high) return high;
-        else return v;
-}
-
 // This method calculates the distance between points where x is the difference between the x-coordinates
 // and y is the difference between the y coordinates
 qreal OpticalFlow::calculateDistance(qreal yDifference, qreal xDifference)

tools/ld-comb-ntsc/opticalflow.h

@@ -34,6 +34,7 @@
 #include <opencv2/core/core.hpp>
 #include <opencv2/video/tracking.hpp>
 
+#include "rgb.h"
 #include "yiqbuffer.h"
 
 class OpticalFlow
@@ -54,7 +55,6 @@ class OpticalFlow
     qint32 framesProcessed;
 
     cv::Mat convertYtoMat(YiqBuffer yiqBuffer);
-    qreal clamp(qreal v, qreal low, qreal high);
     qreal calculateDistance(qreal yDifference, qreal xDifference);
 };
 

tools/ld-comb-ntsc/rgb.cpp

@@ -70,20 +70,13 @@ void RGB::conv(YIQ _y, qreal colourBurstMedian)
     g = y - (0.272 * i) - (0.647 * q);
     b = y - (1.107 * i) + (1.704 * q);
 
-    r = clamp(r, 0, 65535);
-    g = clamp(g, 0, 65535);
-    b = clamp(b, 0, 65535);
+    r = clamp(r, 0.0, 65535.0);
+    g = clamp(g, 0.0, 65535.0);
+    b = clamp(b, 0.0, 65535.0);
 }
 
 // Private methods ----------------------------------------------------------------------------------------------------
 
-double RGB::clamp(double v, double low, double high)
-{
-        if (v < low) return low;
-        else if (v > high) return high;
-        else return v;
-}
-
 double RGB::scaleY(double level)
 {
     // Scale Y to according to the black to white interval

tools/ld-comb-ntsc/rgb.h

@@ -45,8 +45,17 @@ class RGB
     bool whitePoint75;
     bool blackAndWhite;
 
-    double clamp(double v, double low, double high);
     double scaleY(double level);
 };
 
+// Clamp a value to within a fixed range.
+// (Equivalent to C++17's std::clamp.)
+template <typename T>
+static inline const T& clamp(const T& v, const T& low, const T& high)
+{
+    if (v < low) return low;
+    else if (v > high) return high;
+    else return v;
+}
+
 #endif // RGB_H