Factor out the RGB conversion code into a header file.

diff --git a/flow.cpp b/flow.cpp
index 8e823e71f8dc0575debf134a6bb086c13221af3b..47cebba7918c84471583629367192795b7aff19b 100644 (file)
--- a/flow.cpp
+++ b/flow.cpp
@@ -16,6 +16,8 @@
 #include <assert.h>
 #include <stdio.h>
 
+#include "flow2rgb.h"
+
 #include <algorithm>
 #include <memory>
 
@@ -520,40 +522,14 @@ int main(void)
                        float dv = dense_flow[(yy * level_width + x) * 3 + 1];
                        float w = dense_flow[(yy * level_width + x) * 3 + 2];
 
-                       du /= w;
-                       dv /= w;
-
-                       float angle = atan2(dv * level_width, du * level_height);
-                       float magnitude = min(hypot(du * level_width, dv * level_height) / 20.0, 1.0);
-                       
-                       // HSV to RGB (from Wikipedia). Saturation is 1.
-                       float c = magnitude;
-                       float h = (angle + M_PI) * 6.0 / (2.0 * M_PI);
-                       float X = c * (1.0 - fabs(fmod(h, 2.0) - 1.0));
-                       float r = 0.0f, g = 0.0f, b = 0.0f;
-                       if (h < 1.0f) {
-                               r = c; g = X;
-                       } else if (h < 2.0f) {
-                               r = X; g = c;
-                       } else if (h < 3.0f) {
-                               g = c; b = X;
-                       } else if (h < 4.0f) {
-                               g = X; b = c;
-                       } else if (h < 5.0f) {
-                               r = X; b = c;
-                       } else if (h < 6.0f) {
-                               r = c; b = X;
-                       } else {
-                               // h is NaN, so black is fine.
-                       }
-                       float m = magnitude - c;
-                       r += m; g += m; b += m;
-                       r = max(min(r, 1.0f), 0.0f);
-                       g = max(min(g, 1.0f), 0.0f);
-                       b = max(min(b, 1.0f), 0.0f);
-                       putc(lrintf(r * 255.0f), fp);
-                       putc(lrintf(g * 255.0f), fp);
-                       putc(lrintf(b * 255.0f), fp);
+                       du = (du / w) * level_width;
+                       dv = (dv / w) * level_height;
+
+                       uint8_t r, g, b;
+                       flow2rgb(du, dv, &r, &g, &b);
+                       putc(r, fp);
+                       putc(g, fp);
+                       putc(b, fp);
                }
        }
        fclose(fp);

diff --git a/flow2rgb.h b/flow2rgb.h
new file mode 100644 (file)
index 0000000..ca17530
--- /dev/null
+++ b/flow2rgb.h
@@ -0,0 +1,45 @@
+#ifndef _FLOW2RGB_H
+#define _FLOW2RGB_H 1
+
+#include <math.h>
+#include <stdint.h>
+
+#include <algorithm>
+
+// du and dv are in pixels.
+inline void flow2rgb(float du, float dv, uint8_t *rr, uint8_t *gg, uint8_t *bb)
+{
+       float angle = atan2(dv, du);
+       float magnitude = std::min(hypot(du, dv) / 20.0, 1.0);
+       
+       // HSV to RGB (from Wikipedia). Saturation is 1.
+       float c = magnitude;
+       float h = (angle + M_PI) * 6.0 / (2.0 * M_PI);
+       float X = c * (1.0 - fabs(fmod(h, 2.0) - 1.0));
+       float r = 0.0f, g = 0.0f, b = 0.0f;
+       if (h < 1.0f) {
+               r = c; g = X;
+       } else if (h < 2.0f) {
+               r = X; g = c;
+       } else if (h < 3.0f) {
+               g = c; b = X;
+       } else if (h < 4.0f) {
+               g = X; b = c;
+       } else if (h < 5.0f) {
+               r = X; b = c;
+       } else if (h < 6.0f) {
+               r = c; b = X;
+       } else {
+               // h is NaN, so black is fine.
+       }
+       float m = magnitude - c;
+       r += m; g += m; b += m;
+       r = std::max(std::min(r, 1.0f), 0.0f);
+       g = std::max(std::min(g, 1.0f), 0.0f);
+       b = std::max(std::min(b, 1.0f), 0.0f);
+       *rr = lrintf(r * 255.0f);
+       *gg = lrintf(g * 255.0f);
+       *bb = lrintf(b * 255.0f);
+}
+
+#endif  // !defined(_FLOW2RGB_H)