Convert sRGB to linear in movit.white_balance filter.

Patch by Steinar Gunderson.

diff --git a/src/modules/opengl/filter_white_balance.cpp b/src/modules/opengl/filter_white_balance.cpp
index 1b458e7dab6ef12b6d04aba3093decd43166308b..5080bcf473b6c0ee13031f797bf4b1384167a090 100644 (file)
--- a/src/modules/opengl/filter_white_balance.cpp
+++ b/src/modules/opengl/filter_white_balance.cpp
@@ -19,11 +19,22 @@
 
 #include <framework/mlt.h>
 #include <string.h>
+#include <math.h>
 #include <assert.h>
 
 #include "glsl_manager.h"
 #include <movit/white_balance_effect.h>
 
+static double srgb8_to_linear(int c)
+{
+       double x = c / 255.0f;
+       if (x < 0.04045f) {
+               return (1.0/12.92f) * x;
+       } else {
+               return pow((x + 0.055) * (1.0/1.055f), 2.4);
+       }
+}
+
 static int get_image( mlt_frame frame, uint8_t **image, mlt_image_format *format, int *width, int *height, int writable )
 {
        mlt_filter filter = (mlt_filter) mlt_frame_pop_service( frame );
@@ -35,9 +46,9 @@ static int get_image( mlt_frame frame, uint8_t **image, mlt_image_format *format
                mlt_position length = mlt_filter_get_length2( filter, frame );
                int color_int = mlt_properties_anim_get_int( properties, "neutral_color", position, length );
                RGBTriplet color(
-                       float((color_int >> 24) & 0xff) / 255.0f,
-                       float((color_int >> 16) & 0xff) / 255.0f,
-                       float((color_int >> 8) & 0xff) / 255.0f
+                       srgb8_to_linear((color_int >> 24) & 0xff),
+                       srgb8_to_linear((color_int >> 16) & 0xff),
+                       srgb8_to_linear((color_int >> 8) & 0xff)
                );
                bool ok = effect->set_vec3( "neutral_color", (float*) &color );
                ok |= effect->set_float( "output_color_temperature",