cm: higher-quality tonemapping

Author: njdom24

src/protocols/types/ColorManagement.hpp

@@ -6,8 +6,10 @@
 
 #define SDR_MIN_LUMINANCE 0.2
 #define SDR_MAX_LUMINANCE 80.0
+#define SDR_REF_LUMINANCE 80.0
 #define HDR_MIN_LUMINANCE 0.005
 #define HDR_MAX_LUMINANCE 10000.0
+#define HDR_REF_LUMINANCE 203.0
 #define HLG_MAX_LUMINANCE 1000.0
 
 namespace NColorManagement {
@@ -228,6 +230,25 @@ namespace NColorManagement {
             }
         };
 
+        float getTFRefLuminance(int sdrRefLuminance = -1) const {
+            switch (transferFunction) {
+                case CM_TRANSFER_FUNCTION_EXT_LINEAR:
+                case CM_TRANSFER_FUNCTION_ST2084_PQ:
+                case CM_TRANSFER_FUNCTION_HLG: return HDR_REF_LUMINANCE;
+                case CM_TRANSFER_FUNCTION_GAMMA22:
+                case CM_TRANSFER_FUNCTION_GAMMA28:
+                case CM_TRANSFER_FUNCTION_BT1886:
+                case CM_TRANSFER_FUNCTION_ST240:
+                case CM_TRANSFER_FUNCTION_LOG_100:
+                case CM_TRANSFER_FUNCTION_LOG_316:
+                case CM_TRANSFER_FUNCTION_XVYCC:
+                case CM_TRANSFER_FUNCTION_EXT_SRGB:
+                case CM_TRANSFER_FUNCTION_ST428:
+                case CM_TRANSFER_FUNCTION_SRGB:
+                default: return sdrRefLuminance >= 0 ? sdrRefLuminance : SDR_REF_LUMINANCE;
+            }
+        };
+
         uint32_t findId() const;
         uint32_t getId() const;
         uint32_t updateId();

src/render/OpenGL.cpp

@@ -969,6 +969,7 @@ static void getCMShaderUniforms(SShader& shader) {
     shader.uniformLocations[SHADER_DST_TF_RANGE]      = glGetUniformLocation(shader.program, "dstTFRange");
     shader.uniformLocations[SHADER_TARGET_PRIMARIES]  = glGetUniformLocation(shader.program, "targetPrimaries");
     shader.uniformLocations[SHADER_MAX_LUMINANCE]     = glGetUniformLocation(shader.program, "maxLuminance");
+    shader.uniformLocations[SHADER_SRC_REF_LUMINANCE] = glGetUniformLocation(shader.program, "srcRefLuminance");
     shader.uniformLocations[SHADER_DST_MAX_LUMINANCE] = glGetUniformLocation(shader.program, "dstMaxLuminance");
     shader.uniformLocations[SHADER_DST_REF_LUMINANCE] = glGetUniformLocation(shader.program, "dstRefLuminance");
     shader.uniformLocations[SHADER_SDR_SATURATION]    = glGetUniformLocation(shader.program, "sdrSaturation");
@@ -1589,10 +1590,12 @@ void CHyprOpenGLImpl::passCMUniforms(SShader& shader, const NColorManagement::SI
     shader.setUniformFloat2(SHADER_DST_TF_RANGE, targetImageDescription.getTFMinLuminance(needsSDRmod ? sdrMinLuminance : -1),
                             targetImageDescription.getTFMaxLuminance(needsSDRmod ? sdrMaxLuminance : -1));
 
+    shader.setUniformFloat(SHADER_SRC_REF_LUMINANCE, imageDescription.getTFRefLuminance(-1));
+    shader.setUniformFloat(SHADER_DST_REF_LUMINANCE, targetImageDescription.getTFRefLuminance(-1));
+
     const float maxLuminance = imageDescription.luminances.max > 0 ? imageDescription.luminances.max : imageDescription.luminances.reference;
     shader.setUniformFloat(SHADER_MAX_LUMINANCE, maxLuminance * targetImageDescription.luminances.reference / imageDescription.luminances.reference);
     shader.setUniformFloat(SHADER_DST_MAX_LUMINANCE, targetImageDescription.luminances.max > 0 ? targetImageDescription.luminances.max : 10000);
-    shader.setUniformFloat(SHADER_DST_REF_LUMINANCE, targetImageDescription.luminances.reference);
     shader.setUniformFloat(SHADER_SDR_SATURATION, needsSDRmod && m_renderData.pMonitor->m_sdrSaturation > 0 ? m_renderData.pMonitor->m_sdrSaturation : 1.0f);
     shader.setUniformFloat(SHADER_SDR_BRIGHTNESS, needsSDRmod && m_renderData.pMonitor->m_sdrBrightness > 0 ? m_renderData.pMonitor->m_sdrBrightness : 1.0f);
     const auto cacheKey = std::make_pair(imageDescription.getId(), targetImageDescription.getId());
@@ -1709,9 +1712,11 @@ void CHyprOpenGLImpl::renderTextureInternal(SP<CTexture> tex, const CBox& box, c
         shader->setUniformInt(SHADER_TEX_TYPE, texType);
         if (data.cmBackToSRGB) {
             // revert luma changes to avoid black screenshots.
-            // this will likely not be 1:1, and might cause screenshots to be too bright, but it's better than pitch black.
-            imageDescription.luminances = {};
-            passCMUniforms(*shader, imageDescription, NColorManagement::SImageDescription{}, true, -1, -1);
+            imageDescription.luminances = {
+                .min = imageDescription.getTFMinLuminance(-1), .max = imageDescription.getTFMaxLuminance(-1), .reference = imageDescription.getTFRefLuminance(-1)};
+            static auto PSDREOTF      = CConfigValue<Hyprlang::INT>("render:cm_sdr_eotf");
+            auto        chosenSdrEotf = *PSDREOTF > 0 ? NColorManagement::CM_TRANSFER_FUNCTION_GAMMA22 : NColorManagement::CM_TRANSFER_FUNCTION_SRGB;
+            passCMUniforms(*shader, imageDescription, NColorManagement::SImageDescription{.transferFunction = chosenSdrEotf}, true, -1, -1);
         } else
             passCMUniforms(*shader, imageDescription);
     }

src/render/Shader.hpp

@@ -16,6 +16,7 @@ enum eShaderUniform : uint8_t {
     SHADER_DST_TF_RANGE,
     SHADER_TARGET_PRIMARIES,
     SHADER_MAX_LUMINANCE,
+    SHADER_SRC_REF_LUMINANCE,
     SHADER_DST_MAX_LUMINANCE,
     SHADER_DST_REF_LUMINANCE,
     SHADER_SDR_SATURATION,

src/render/shaders/glsl/CM.glsl

@@ -2,6 +2,7 @@ uniform vec2 srcTFRange;
 uniform vec2 dstTFRange;
 
 uniform float maxLuminance;
+uniform float srcRefLuminance;
 uniform float dstMaxLuminance;
 uniform float dstRefLuminance;
 uniform float sdrSaturation;
@@ -387,24 +388,20 @@ vec4 tonemap(vec4 color, mat3 dstXYZ) {
         PQ_INV_M1
     ) * HDR_MAX_LUMINANCE;
 
-    float srcScale = maxLuminance / dstRefLuminance;
-    float dstScale = dstMaxLuminance / dstRefLuminance;
+    float linearPart = min(luminance, dstRefLuminance);
+    float luminanceAboveRef = max(luminance - dstRefLuminance, 0.0);
+    float maxExcessLuminance = max(maxLuminance - dstRefLuminance, 1.0);
+    float shoulder = log((luminanceAboveRef / maxExcessLuminance + 1.0) * (M_E - 1.0));
+    float mappedHigh = shoulder * (dstMaxLuminance - dstRefLuminance);
+    float newLum = clamp(linearPart + mappedHigh, 0.0, dstMaxLuminance);
 
-    float minScale = min(srcScale, 1.5);
-    float dimming = 1.0 / clamp(minScale / dstScale, 1.0, minScale);
-    float refLuminance = dstRefLuminance * dimming;
+    float newIpq = tfPQ(vec3(newLum / HDR_MAX_LUMINANCE)).r;
+    ICtCp[0] = clamp(newIpq, 0.0, 1.0);
 
-    float low = min(luminance * dimming, refLuminance);
-    float highlight = clamp((luminance / dstRefLuminance - 1.0) / (srcScale - 1.0), 0.0, 1.0);
-    float high = log(highlight * (M_E - 1.0) + 1.0) * (dstMaxLuminance - refLuminance);
-    luminance = low + high;
+    // scale src to dst reference
+    float refScale = dstRefLuminance / srcRefLuminance;
 
-    E = pow(clamp(ICtCp[0], 0.0, 1.0), PQ_M1);
-    ICtCp[0] = pow(
-        (PQ_C1 + PQ_C2 * E) / (1.0 + PQ_C3 * E),
-        PQ_M2
-    ) / HDR_MAX_LUMINANCE;
-    return vec4(fromLMS * toLinear(vec4(ICtCpPQInv * ICtCp, 1.0), CM_TRANSFER_FUNCTION_ST2084_PQ).rgb * HDR_MAX_LUMINANCE, color[3]);
+    return vec4(fromLMS * toLinear(vec4(ICtCpPQInv * ICtCp, 1.0), CM_TRANSFER_FUNCTION_ST2084_PQ).rgb * HDR_MAX_LUMINANCE * refScale, color[3]); 
 }
 
 vec4 doColorManagement(vec4 pixColor, int srcTF, int dstTF, mat4x2 dstPrimaries) {