Squash linear gamma back into the sRGB curve at the end.

diff --git a/Makefile b/Makefile
index 728b6f013117a552e5abb4f513159d6d531585eb..4dbaf121fc930491f9b1f76641d01f541f469430 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@ CXX=g++
 CXXFLAGS=-Wall -g
 LDFLAGS=-lSDL -lSDL_image -lGL
 OBJS=main.o util.o widgets.o effect.o effect_chain.o
-OBJS += lift_gamma_gain_effect.o gamma_expansion_effect.o colorspace_conversion_effect.o
+OBJS += lift_gamma_gain_effect.o gamma_expansion_effect.o gamma_compression_effect.o colorspace_conversion_effect.o
 
 test: $(OBJS)
        $(CXX) -o test $(OBJS) $(LDFLAGS)

diff --git a/effect_chain.cpp b/effect_chain.cpp
index a8381505109affe8ade2becd09009c58b15b1233..56d470fb572e7764e0c78d02bf8d8a0e0a08f506 100644 (file)
--- a/effect_chain.cpp
+++ b/effect_chain.cpp
@@ -10,6 +10,7 @@
 #include "util.h"
 #include "effect_chain.h"
 #include "gamma_expansion_effect.h"
+#include "gamma_compression_effect.h"
 #include "lift_gamma_gain_effect.h"
 #include "colorspace_conversion_effect.h"
 #include "texture_enum.h"
@@ -42,24 +43,34 @@ Effect *instantiate_effect(EffectId effect)
        assert(false);
 }
 
+void EffectChain::normalize_to_linear_gamma()
+{
+       GammaExpansionEffect *gamma_conversion = new GammaExpansionEffect();
+       gamma_conversion->set_int("source_curve", current_gamma_curve);
+       effects.push_back(gamma_conversion);
+       current_gamma_curve = GAMMA_LINEAR;
+}
+
+void EffectChain::normalize_to_srgb()
+{
+       assert(current_gamma_curve == GAMMA_LINEAR);
+       ColorSpaceConversionEffect *colorspace_conversion = new ColorSpaceConversionEffect();
+       colorspace_conversion->set_int("source_space", current_color_space);
+       colorspace_conversion->set_int("destination_space", COLORSPACE_sRGB);
+       effects.push_back(colorspace_conversion);
+       current_color_space = COLORSPACE_sRGB;
+}
+
 Effect *EffectChain::add_effect(EffectId effect_id)
 {
        Effect *effect = instantiate_effect(effect_id);
 
        if (effect->needs_linear_light() && current_gamma_curve != GAMMA_LINEAR) {
-               GammaExpansionEffect *gamma_conversion = new GammaExpansionEffect();
-               gamma_conversion->set_int("source_curve", current_gamma_curve);
-               effects.push_back(gamma_conversion);
-               current_gamma_curve = GAMMA_LINEAR;
+               normalize_to_linear_gamma();
        }
 
        if (effect->needs_srgb_primaries() && current_color_space != COLORSPACE_sRGB) {
-               assert(current_gamma_curve == GAMMA_LINEAR);
-               ColorSpaceConversionEffect *colorspace_conversion = new ColorSpaceConversionEffect();
-               colorspace_conversion->set_int("source_space", current_color_space);
-               colorspace_conversion->set_int("destination_space", COLORSPACE_sRGB);
-               effects.push_back(colorspace_conversion);
-               current_color_space = COLORSPACE_sRGB;
+               normalize_to_srgb();
        }
 
        // not handled yet
@@ -113,6 +124,19 @@ std::string replace_prefix(const std::string &text, const std::string &prefix)
 
 void EffectChain::finalize()
 {
+       // TODO: If we want a non-sRGB output color space, convert.
+
+       if (current_gamma_curve != output_format.gamma_curve) {
+               if (current_gamma_curve != GAMMA_LINEAR) {
+                       normalize_to_linear_gamma();
+               }
+               assert(current_gamma_curve == GAMMA_LINEAR);
+               GammaCompressionEffect *gamma_conversion = new GammaCompressionEffect();
+               gamma_conversion->set_int("destination_curve", output_format.gamma_curve);
+               effects.push_back(gamma_conversion);
+               current_gamma_curve = output_format.gamma_curve;
+       }
+
        std::string frag_shader = read_file("header.glsl");
 
        for (unsigned i = 0; i < effects.size(); ++i) {

diff --git a/effect_chain.h b/effect_chain.h
index 9622abc0eef1abf824b3b83f2c9fbdd151eef104..045c9aa7832f7885570eccd69d7670ce39d92e28 100644 (file)
--- a/effect_chain.h
+++ b/effect_chain.h
@@ -46,6 +46,9 @@ public:
        void render_to_screen(unsigned char *src);
 
 private:
+       void normalize_to_linear_gamma();
+       void normalize_to_srgb();
+
        unsigned width, height;
        ImageFormat input_format, output_format;
        std::vector<Effect *> effects;

diff --git a/gamma_compression_effect.cpp b/gamma_compression_effect.cpp
new file mode 100644 (file)
index 0000000..2c88b02
--- /dev/null
+++ b/gamma_compression_effect.cpp
@@ -0,0 +1,23 @@
+#include <assert.h>
+
+#include "gamma_compression_effect.h"
+#include "util.h"
+
+GammaCompressionEffect::GammaCompressionEffect()
+       : destination_curve(GAMMA_LINEAR)
+{
+       register_int("destination_curve", (int *)&destination_curve);
+}
+
+std::string GammaCompressionEffect::output_glsl()
+{
+       switch (destination_curve) {
+       case GAMMA_sRGB:
+               return read_file("gamma_compression_effect_srgb.glsl");
+       case GAMMA_REC_709:  // and GAMMA_REC_601
+               // Not implemented yet.
+               assert(false);
+       default:
+               assert(false);
+       }
+}

diff --git a/gamma_compression_effect.h b/gamma_compression_effect.h
new file mode 100644 (file)
index 0000000..ec2a77a
--- /dev/null
+++ b/gamma_compression_effect.h
@@ -0,0 +1,16 @@
+#ifndef _GAMMA_COMPRESSION_EFFECT_H 
+#define _GAMMA_COMPRESSION_EFFECT_H 1
+
+#include "effect.h"
+#include "effect_chain.h"
+
+class GammaCompressionEffect : public Effect {
+public:
+       GammaCompressionEffect();
+       std::string output_glsl();
+
+private:
+       GammaCurve destination_curve;
+};
+
+#endif // !defined(_GAMMA_COMPRESSION_EFFECT_H)

diff --git a/gamma_compression_effect_srgb.glsl b/gamma_compression_effect_srgb.glsl
new file mode 100644 (file)
index 0000000..2d53e08
--- /dev/null
+++ b/gamma_compression_effect_srgb.glsl
@@ -0,0 +1,31 @@
+// Compress to sRGB gamma curve.
+
+#if 0
+
+// if we have the lut
+uniform sampler1D PREFIX(srgb_tex);
+
+vec4 FUNCNAME(vec2 tc) {
+       vec4 x = LAST_INPUT(tc);
+
+       x.r = texture1D(PREFIX(srgb_tex), x.r).x;
+       x.g = texture1D(PREFIX(srgb_tex), x.g).x;
+       x.b = texture1D(PREFIX(srgb_tex), x.b).x;
+
+       return x;
+}
+
+#else
+
+// use arithmetic (slow)
+vec4 FUNCNAME(vec2 tc) {
+       vec4 x = LAST_INPUT(tc);
+
+       vec3 a = vec3(12.92) * x.rgb;
+       vec3 b = vec3(1.055) * pow(x.rgb, vec3(1.0/2.4)) - vec3(0.055);
+       vec3 f = vec3(greaterThan(x.rgb, vec3(0.0031308)));
+
+       return vec4(mix(a, b, f), x.a); 
+}
+ 
+#endif