Apply slanted profile to contrast values

averne · Nov 5, 2024 · 3149127 · 3149127
1 parent 03d4c3b
commit 3149127
Show file tree

Hide file tree

Showing 5 changed files with 11 additions and 4 deletions.
diff --git a/application/src/gfx.cpp b/application/src/gfx.cpp
@@ -349,7 +349,7 @@ void render_preview(FizeauSettings &settings, Component components, Component fi
     coeffs = dot(coeffs, m);
 
     // Apply contrast multiplier
-    m[0] = m[4] = m[8] = settings.contrast;
+    m[0] = m[4] = m[8] = contrast_slant(settings.contrast);
     coeffs = dot(coeffs, m);
 
     // Apply saturation

diff --git a/application/src/gui.cpp b/application/src/gui.cpp
@@ -480,7 +480,7 @@ void draw_graph_window(Config &ctx) {
     std::array<std::uint16_t, 256> lut1;
     std::array<std::uint16_t, 960> lut2;
 
-    float off = (1.0f - set.contrast) / 2.0f;
+    float off = (1.0f - contrast_slant(set.contrast)) / 2.0f;
     degamma_ramp(lut1.data(), lut1.size(), DEFAULT_GAMMA, 8);
     regamma_ramp(lut2.data(), lut2.size(), set.gamma, 8, 0.0f, 1.0f, off);
 

diff --git a/common/include/color.hpp b/common/include/color.hpp
@@ -40,6 +40,7 @@ std::tuple<float, float, float> whitepoint(Temperature temperature);
 ColorMatrix hue_matrix(Hue hue);
 ColorMatrix saturation_matrix(Saturation sat);
 
+Contrast contrast_slant(Contrast c);
 float degamma(float x, Gamma gamma);
 float regamma(float x, Gamma gamma);
 

diff --git a/common/src/color.cpp b/common/src/color.cpp
@@ -107,6 +107,11 @@ ColorMatrix saturation_matrix(Saturation sat) {
     };
 }
 
+Contrast contrast_slant(Contrast c) {
+    c -= 1.0f;
+    return c * c * c + 1.0f;
+}
+
 float degamma(float x, Gamma gamma) {
     if (x <= 0.040045f) // x * pow((0.040045 + 0.055) / (1.0 + 0.055), gamma) / 0.040045;
         return x * 24.972f * std::pow(0.090f, gamma);

diff --git a/sysmodule/src/nvdisp.cpp b/sysmodule/src/nvdisp.cpp
@@ -40,7 +40,8 @@ Cmu calculate_cmu(FizeauSettings &settings, Component components, Component filt
     coeffs = dot(coeffs, m);
 
     // Apply contrast multiplier
-    m[0] = m[4] = m[8] = settings.contrast;
+    auto c = contrast_slant(settings.contrast);
+    m[0] = m[4] = m[8] = c;
     coeffs = dot(coeffs, m);
 
     // Apply saturation
@@ -58,7 +59,7 @@ Cmu calculate_cmu(FizeauSettings &settings, Component components, Component filt
         std::copy_n(coeffs.begin() + 6, 3, &cmu.krb);
 
     // Calculate gamma ramps, with contrast offset
-    float off = (1.0f - settings.contrast) / 2.0f;
+    float off = (1.0f - c) / 2.0f;
     degamma_ramp(cmu.lut_1.data(), cmu.lut_1.size(), DEFAULT_GAMMA, 12);                                // Set the LUT1 with a fixed gamma corresponding to the incoming data
     regamma_ramp(cmu.lut_2.data(), 512, settings.gamma, 8, 0.0f, 0.125f, off);                          // Set the first part of LUT2 (more precision in darker components)
     regamma_ramp(cmu.lut_2.data() + 512, cmu.lut_2.size() - 512, settings.gamma, 8, 0.125f, 1.0f, off); // Set the second part of LUT2 (less precision in brighter components)