Add a color curve post-processor

diff --git a/source/colorcurve.cpp b/source/colorcurve.cpp
new file mode 100644 (file)
index 0000000..95c8249
--- /dev/null
+++ b/source/colorcurve.cpp
@@ -0,0 +1,77 @@
+#include "colorcurve.h"
+#include "mesh.h"
+#include "shader.h"
+#include "texture2d.h"
+
+using namespace std;
+
+namespace {
+
+static const char fragment_src[] =
+       "uniform sampler2D texture;\n"
+       "uniform float peak;\n"
+       "uniform float brightness;\n"
+       "varying vec2 texcoord;\n"
+       "void main()\n"
+       "{\n"
+       "       vec4 sample = texture2D(texture, texcoord);\n"
+       "       float maxc = max(sample.r, max(sample.g, sample.b));\n"
+       "       if(maxc>1.0-peak)\n"
+       "       {\n"
+       "               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-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-x*x)*peak);\n"
+       "               }\n"
+       "               gl_FragColor.a = sample.a;\n"
+       "       }\n"
+       "       else\n"
+       "               gl_FragColor = sample;\n"
+       "}";
+
+}
+
+namespace Msp {
+namespace GL {
+
+ColorCurve::ColorCurve():
+       quad(get_fullscreen_quad())
+{
+       shprog.attach_shader(get_fullscreen_vertex_shader());
+       Shader *fs = new Shader(FRAGMENT_SHADER, fragment_src);
+       shprog.attach_shader_owned(fs);
+       shprog.link();
+
+       set_peak(0.2);
+       set_brightness(1.5);
+}
+
+void ColorCurve::set_peak(float p)
+{
+       if(p<0 || p>1)
+               throw invalid_argument("ColorCurve::set_peak");
+       shdata.uniform("peak", p);
+}
+
+void ColorCurve::set_brightness(float b)
+{
+       if(b<1)
+               throw invalid_argument("ColorCurve::set_brightness");
+       shdata.uniform("brightness", b);
+}
+
+void ColorCurve::render(const Texture2D &color_buf, const Texture2D &)
+{
+       Bind _bind_shader(shprog);
+       shdata.apply();
+       Bind _bind_tex(color_buf);
+       quad.draw();
+}
+
+} // namespace GL
+} // namespace Msp

diff --git a/source/colorcurve.h b/source/colorcurve.h
new file mode 100644 (file)
index 0000000..82a8526
--- /dev/null
+++ b/source/colorcurve.h
@@ -0,0 +1,42 @@
+#ifndef COLORCURVE_H_
+#define COLORCURVE_H_
+
+#include "postprocessor.h"
+#include "program.h"
+#include "programdata.h"
+
+namespace Msp {
+namespace GL {
+
+/**
+Processes oversaturated colors to preserve hues.  When one color component 
+exceeds 1.0, the others are scaled towards white.  A transition curve is also
+applied near 1.0 to prevent the abrupt change in the gradient.
+
+Only makes sense when used in an HDR framebuffer.
+*/
+class ColorCurve: public PostProcessor
+{
+private:
+       Program shprog;
+       ProgramData shdata;
+       const Mesh &quad;
+
+public:
+       ColorCurve();
+
+       /// Sets the size of the peak zone.  Must be between 0 and 1, inclusive.
+       void set_peak(float);
+
+       /** Sets brightness for oversaturated colors.  Must be >= 1.  Suggested
+       values are between 1.5 and 2.0; a value of 1.0 will clamp colors to the
+       saturated value. */
+       void set_brightness(float);
+
+       virtual void render(const Texture2D &, const Texture2D &);
+};
+
+} // namespace GL
+} // namespace Msp
+
+#endif