bugfix to preserve negative color components. rename threshold rgb to cmy. default shadow rolloff to 0.0.

Author: Jed Smith

GamutCompress.blink

@@ -197,9 +197,19 @@ kernel GamutCompression : public ImageComputationKernel<ePixelWise> {
     // achromatic axis 
     float ach = max(rgb.x, max(rgb.y, rgb.z));
 
-    // achromatic with shadow rolloff below shd_rolloff threshold
-    float ach_shd = 1.0f-( (1.0f-ach)<(1.0f-shd_rolloff)?(1.0f-ach):(1.0f-shd_rolloff)+shd_rolloff*tanh((((1.0f-ach)-(1.0f-shd_rolloff))/shd_rolloff)));
-
+    // achromatic shadow rolloff
+    float ach_shd;
+    if (shd_rolloff < 0.004f) {
+      // disable shadow rolloff functionality. 
+      // values below 0.004 cause strange behavior, actually increasing distance in some cases.
+      // if ach < 0.0 and shd_rolloff is disabled, take absolute value. This preserves negative components after compression.
+      ach_shd = fabs(ach);
+    } else {
+      // lift ach below threshold using a tanh compression function. 
+      // this reduces large distance values in shadow grain, which can cause differences when inverting.
+      ach_shd = 1.0f-((1.0f-ach)<(1.0f-shd_rolloff)?(1.0f-ach):(1.0f-shd_rolloff)+shd_rolloff*tanh((((1.0f-ach)-(1.0f-shd_rolloff))/shd_rolloff)));
+    } 
+    
     // distance from the achromatic axis for each color component aka inverse rgb ratios
     // distance is normalized by achromatic, so that 1.0f is at gamut boundary, avoid 0 div
     float3 dist = ach_shd == 0 ? float3(0.0f, 0.0f, 0.0f) : (ach-rgb)/ach_shd;

GamutCompress.dctl

@@ -1,8 +1,8 @@
-DEFINE_UI_PARAMS(threshold_r, threshold r, DCTLUI_SLIDER_FLOAT, 0.2f, 0.0f, 0.6f, 0.0f);
-DEFINE_UI_PARAMS(threshold_g, threshold g, DCTLUI_SLIDER_FLOAT, 0.2f, 0.0f, 0.6f, 0.0f);
-DEFINE_UI_PARAMS(threshold_b, threshold b, DCTLUI_SLIDER_FLOAT, 0.2f, 0.0f, 0.6f, 0.0f);
+DEFINE_UI_PARAMS(threshold_c, threshold c, DCTLUI_SLIDER_FLOAT, 0.2f, 0.0f, 0.6f, 0.0f);
+DEFINE_UI_PARAMS(threshold_m, threshold m, DCTLUI_SLIDER_FLOAT, 0.2f, 0.0f, 0.6f, 0.0f);
+DEFINE_UI_PARAMS(threshold_y, threshold y, DCTLUI_SLIDER_FLOAT, 0.2f, 0.0f, 0.6f, 0.0f);
 DEFINE_UI_PARAMS(power, power, DCTLUI_SLIDER_FLOAT, 1.2f, 1.0f, 3.0f, 1.0f);
-DEFINE_UI_PARAMS(shd_rolloff, shd rolloff, DCTLUI_SLIDER_FLOAT, 0.03f, 0.0f, 0.1f, 0.0f);
+DEFINE_UI_PARAMS(shd_rolloff, shd rolloff, DCTLUI_SLIDER_FLOAT, 0.0f, 0.0f, 0.03f, 0.0f);
 DEFINE_UI_PARAMS(cyan, cyan, DCTLUI_SLIDER_FLOAT, 0.09f, 0.0f, 1.0f, 0.0f);
 DEFINE_UI_PARAMS(magenta, magenta, DCTLUI_SLIDER_FLOAT, 0.24f, 0.0f, 1.0f, 0.0f);
 DEFINE_UI_PARAMS(yellow, yellow, DCTLUI_SLIDER_FLOAT, 0.12f, 0.0f, 1.0f, 0.0f);
@@ -224,9 +224,9 @@ __DEVICE__ float3 transform(int p_Width, int p_Height, int p_X, int p_Y, float p
 
   // thr is the percentage of the core gamut to protect: the complement of threshold.
   float3 thr = make_float3(
-    1.0f-_fmaxf(0.00001, threshold_r),
-    1.0f-_fmaxf(0.00001, threshold_g),
-    1.0f-_fmaxf(0.00001, threshold_b));
+    1.0f-_fmaxf(0.00001, threshold_c),
+    1.0f-_fmaxf(0.00001, threshold_m),
+    1.0f-_fmaxf(0.00001, threshold_y));
 
   // lim is the max distance from the gamut boundary that will be compressed
   // 0 is a no-op, 1 will compress colors from a distance of 2.0 from achromatic to the gamut boundary
@@ -249,9 +249,19 @@ __DEVICE__ float3 transform(int p_Width, int p_Height, int p_X, int p_Y, float p
   // achromatic axis 
   float ach = _fmaxf(rgb.x, _fmaxf(rgb.y, rgb.z));
 
-  // achromatic with shadow rolloff below shd_rolloff threshold
-  float ach_shd = 1.0f-( (1.0f-ach)<(1.0f-shd_rolloff)?(1.0f-ach):(1.0f-shd_rolloff)+shd_rolloff*_tanhf((((1.0f-ach)-(1.0f-shd_rolloff))/shd_rolloff)));
-
+  // achromatic shadow rolloff
+  float ach_shd;
+  if (shd_rolloff < 0.004f) {
+    // disable shadow rolloff functionality. 
+    // values below 0.004 cause strange behavior, actually increasing distance in some cases.
+    // if ach < 0.0 and shd_rolloff is disabled, take absolute value. This preserves negative components after compression.
+    ach_shd = _fabs(ach);
+  } else {
+    // lift ach below threshold using a tanh compression function. 
+    // this reduces large distance values in shadow grain, which can cause differences when inverting.
+    ach_shd = 1.0f-((1.0f-ach)<(1.0f-shd_rolloff)?(1.0f-ach):(1.0f-shd_rolloff)+shd_rolloff*_tanhf((((1.0f-ach)-(1.0f-shd_rolloff))/shd_rolloff)));
+  } 
+  
   // distance from the achromatic axis for each color component aka inverse rgb ratios
   float3 dist;
   dist.x = ach_shd == 0.0f ? 0.0f : (ach-rgb.x)/ach_shd;

GamutCompress.fuse

@@ -106,23 +106,23 @@ function Create()
     INP_Default = 0.0,
   })
 
-  InThresholdR = self:AddInput("threshold_r", "threshold_r", {
+  InThresholdR = self:AddInput("threshold_c", "threshold_c", {
     LINKID_DataType = "Number",
     INPID_InputControl = "SliderControl",
     INP_Default = 0.2,
     INP_MinAllowed = 0.0001,
     INP_MaxScale = 0.6,
   })
 
-  InThresholdG = self:AddInput("threshold_g", "threshold_g", {
+  InThresholdG = self:AddInput("threshold_m", "threshold_m", {
     LINKID_DataType = "Number",
     INPID_InputControl = "SliderControl",
     INP_Default = 0.2,
     INP_MinAllowed = 0.0001,
     INP_MaxScale = 0.6,
   })
 
-  InThresholdB = self:AddInput("threshold_b", "threshold_b", {
+  InThresholdB = self:AddInput("threshold_y", "threshold_y", {
     LINKID_DataType = "Number",
     INPID_InputControl = "SliderControl",
     INP_Default = 0.2,
@@ -141,9 +141,9 @@ function Create()
   InShdRolloff = self:AddInput("shd rolloff", "shd rolloff", {
     LINKID_DataType = "Number",
     INPID_InputControl = "SliderControl",
-    INP_Default = 0.03,
+    INP_Default = 0.0,
     INP_MinAllowed = 0.0,
-    INP_MaxScale = 0.1,
+    INP_MaxScale = 0.03,
   })
 
   self:BeginControlNest("distance limits", "distance limits", true, {})
@@ -204,9 +204,9 @@ function Process(req)
 
     params.method = InMethod:GetValue(req).Value
     params.hexagonal = InHexagonal:GetValue(req).Value
-    params.threshold_r = InThresholdR:GetValue(req).Value
-    params.threshold_g = InThresholdG:GetValue(req).Value
-    params.threshold_b = InThresholdB:GetValue(req).Value
+    params.threshold_c = InThresholdR:GetValue(req).Value
+    params.threshold_m = InThresholdG:GetValue(req).Value
+    params.threshold_y = InThresholdB:GetValue(req).Value
     params.power = InPower:GetValue(req).Value
     params.shd_rolloff = InShdRolloff:GetValue(req).Value
     params.cyan = InCyan:GetValue(req).Value
@@ -235,9 +235,9 @@ end
 SolidParams = [[
   int method;
   int hexagonal;
-  float threshold_r;
-  float threshold_g;
-  float threshold_b;
+  float threshold_c;
+  float threshold_m;
+  float threshold_y;
   float power;
   float shd_rolloff;
   float cyan;
@@ -410,9 +410,9 @@ SolidKernel = [[
 
     // thr is the percentage of the core gamut to protect: the complement of threshold.
     float3 thr = make_float3(
-      1.0f-_fmaxf(0.0001f, params->threshold_r),
-      1.0f-_fmaxf(0.0001f, params->threshold_g),
-      1.0f-_fmaxf(0.0001f, params->threshold_b));
+      1.0f-_fmaxf(0.0001f, params->threshold_c),
+      1.0f-_fmaxf(0.0001f, params->threshold_m),
+      1.0f-_fmaxf(0.0001f, params->threshold_y));
 
     // lim is the max distance from the gamut boundary that will be compressed
     // 0 is a no-op, 1 will compress colors from a distance of 2.0 from achromatic to the gamut boundary
@@ -435,8 +435,18 @@ SolidKernel = [[
     // achromatic axis 
     float ach = _fmaxf(rgb.x, _fmaxf(rgb.y, rgb.z));
 
-    // achromatic with shadow rolloff below shd_rolloff threshold
-    float ach_shd = 1.0f-( (1.0f-ach)<(1.0f-params->shd_rolloff)?(1.0f-ach):(1.0f-params->shd_rolloff)+params->shd_rolloff*_tanhf((((1.0f-ach)-(1.0f-params->shd_rolloff))/params->shd_rolloff)));
+    // achromatic shadow rolloff
+    float ach_shd;
+    if (params->shd_rolloff < 0.004f) {
+      // disable shadow rolloff functionality. 
+      // values below 0.004 cause strange behavior, actually increasing distance in some cases.
+      // if ach < 0.0 and shd_rolloff is disabled, take absolute value. This preserves negative components after compression.
+      ach_shd = _fabs(ach);
+    } else {
+      // lift ach below threshold using a tanh compression function. 
+      // this reduces large distance values in shadow grain, which can cause differences when inverting.
+      ach_shd = 1.0f-((1.0f-ach)<(1.0f-params->shd_rolloff)?(1.0f-ach):(1.0f-params->shd_rolloff)+params->shd_rolloff*_tanhf((((1.0f-ach)-(1.0f-params->shd_rolloff))/params->shd_rolloff)));
+    } 
 
     // distance from the achromatic axis for each color component aka inverse rgb ratios
     float3 dist;

GamutCompress.glsl

@@ -236,8 +236,18 @@ void main() {
   // achromatic axis 
   float ach = max(rgb.x, max(rgb.y, rgb.z));
 
-  // achromatic with shadow rolloff below shd_rolloff threshold
-  float ach_shd = 1.0-((1.0-ach)<(1.0-shd_rolloff)?(1.0-ach):(1.0-shd_rolloff)+shd_rolloff*tanh((((1.0-ach)-(1.0-shd_rolloff))/shd_rolloff)));
+  // achromatic shadow rolloff
+  float ach_shd;
+  if (shd_rolloff < 0.004) {
+    // disable shadow rolloff functionality. 
+    // values below 0.004 cause strange behavior, actually increasing distance in some cases.
+    // if ach < 0.0 and shd_rolloff is disabled, take absolute value. This preserves negative components after compression.
+    ach_shd = abs(ach);
+  } else {
+    // lift ach below threshold using a tanh compression function. 
+    // this reduces large distance values in shadow grain, which can cause differences when inverting.
+    ach_shd = 1.0-((1.0-ach)<(1.0-shd_rolloff)?(1.0-ach):(1.0-shd_rolloff)+shd_rolloff*tanh((((1.0-ach)-(1.0-shd_rolloff))/shd_rolloff)));
+  }
 
   // distance from the achromatic axis for each color component aka inverse rgb ratios
   vec3 dist;