Add gamma correction and sRGB conversion support to ColorCurve

diff --git a/source/colorcurve.cpp b/source/colorcurve.cpp
index ae09b7e62a9b93da283a3918727e32c2cd9642d2..6351ea20bb252c7402bf129e3115dcb6c7f24e5e 100644 (file)
--- a/source/colorcurve.cpp
+++ b/source/colorcurve.cpp
@@ -1,3 +1,4 @@
+#include <cmath>
 #include "colorcurve.h"
 #include "mesh.h"
 #include "shader.h"
@@ -9,6 +10,7 @@ namespace {
 
 static const char fragment_src[] =
        "uniform sampler2D texture;\n"
+       "uniform sampler1D curve;\n"
        "uniform float peak;\n"
        "uniform float brightness;\n"
        "varying vec2 texcoord;\n"
@@ -21,17 +23,15 @@ static const char fragment_src[] =
        "               vec3 saturated = sample.rgb/maxc;\n"
        "               if(maxc>1.0+peak)\n"
        "               {\n"
-       "                       gl_FragColor.rgb = mix(vec3(1.0), saturated, 1.0/pow(brightness, maxc-1.0-peak));\n"
+       "                       sample.rgb = mix(vec3(1.0), saturated, 1.0/pow(brightness, maxc-1.0-peak));\n"
        "               }\n"
        "               else\n"
        "               {\n"
        "                       float x = (1.0+peak-maxc)/(2.0*peak);\n"
-       "                       gl_FragColor.rgb = saturated.rgb*(1.0-peak+(1.0-x*x)*peak);\n"
+       "                       sample.rgb = saturated.rgb*(1.0-peak+(1.0-x*x)*peak);\n"
        "               }\n"
-       "               gl_FragColor.a = sample.a;\n"
        "       }\n"
-       "       else\n"
-       "               gl_FragColor = sample;\n"
+       "       gl_FragColor = vec4(texture1D(curve, sample.r).r, texture1D(curve, sample.g).r, texture1D(curve, sample.b).r, sample.a);\n"
        "}";
 
 }
@@ -46,8 +46,16 @@ ColorCurve::ColorCurve():
        shprog.attach_shader_owned(new FragmentShader(fragment_src));
        shprog.link();
 
+       shdata.uniform("texture", 0);
+       shdata.uniform("curve", 1);
+
+       curve.storage(LUMINANCE, 256);
+       curve.set_min_filter(LINEAR);
+       curve.set_wrap(CLAMP_TO_EDGE);
+
        set_peak(0.2);
        set_brightness(1.5);
+       set_linear();
 }
 
 void ColorCurve::set_peak(float p)
@@ -64,11 +72,40 @@ void ColorCurve::set_brightness(float b)
        shdata.uniform("brightness", b);
 }
 
+void ColorCurve::set_gamma(float g)
+{
+       if(g<0.1 || g>10)
+               throw invalid_argument("ColorCurve::set_gamma");
+
+       unsigned char curve_data[256];
+       for(unsigned i=0; i<256; ++i)
+               curve_data[i] = pow(i/255.0f, 1/g)*255+0.5f;
+       curve.image(0, LUMINANCE, UNSIGNED_BYTE, curve_data);
+}
+
+void ColorCurve::set_srgb()
+{
+       unsigned char curve_data[256];
+       curve_data[0] = 0;
+       for(unsigned i=1; i<256; ++i)
+               curve_data[i] = (1.055*pow(i/255.0f, 1/2.4f)-0.055)*255+0.5;
+       curve.image(0, LUMINANCE, UNSIGNED_BYTE, curve_data);
+}
+
+void ColorCurve::set_linear()
+{
+       unsigned char curve_data[256];
+       for(unsigned i=0; i<256; ++i)
+               curve_data[i] = i;
+       curve.image(0, LUMINANCE, UNSIGNED_BYTE, curve_data);
+}
+
 void ColorCurve::render(const Texture2D &color_buf, const Texture2D &)
 {
        Bind _bind_shader(shprog);
        shdata.apply();
        Bind _bind_tex(color_buf);
+       Bind _bind_curve(curve, 1);
        quad.draw();
 }
 

diff --git a/source/colorcurve.h b/source/colorcurve.h
index 74a19d04bc916878635d23dcaf24708be6989d36..75e7fd302a76a2bea330162942c7c881379dd2c5 100644 (file)
--- a/source/colorcurve.h
+++ b/source/colorcurve.h
@@ -4,6 +4,7 @@
 #include "postprocessor.h"
 #include "program.h"
 #include "programdata.h"
+#include "texture1d.h"
 
 namespace Msp {
 namespace GL {
@@ -20,6 +21,7 @@ class ColorCurve: public PostProcessor
 private:
        Program shprog;
        ProgramData shdata;
+       Texture1D curve;
        const Mesh &quad;
 
 public:
@@ -33,6 +35,10 @@ public:
        saturated value. */
        void set_brightness(float);
 
+       void set_gamma(float);
+       void set_srgb();
+       void set_linear();
+
        virtual void render(const Texture2D &, const Texture2D &);
 };