use pigment mode for smudge sampling

blend additive and subtractive methods
limit sampling to small percentage of pixels

Author: briend

brushmodes.c

@@ -446,42 +446,66 @@ void get_color_pixels_accumulate (uint16_t * mask,
                                   float * sum_r,
                                   float * sum_g,
                                   float * sum_b,
-                                  float * sum_a
+                                  float * sum_a,
+                                  float paint
                                   ) {
 
 
-  // The sum of a 64x64 tile fits into a 32 bit integer, but the sum
-  // of an arbitrary number of tiles may not fit. We assume that we
-  // are processing a single tile at a time, so we can use integers.
-  // But for the result we need floats.
+  // Sample the canvas as additive and subtractive
+  // According to paint parameter
+  // Average the results normally
+  // Only sample a random selection of pixels
 
-  uint32_t weight = 0;
-  uint32_t r = 0;
-  uint32_t g = 0;
-  uint32_t b = 0;
-  uint32_t a = 0;
+  float avg_spectral[10] = {0};
+  float avg_rgb[3] = {*sum_r, *sum_g, *sum_b};
+  if (paint > 0.0f) {
+    rgb_to_spectral(*sum_r, *sum_g, *sum_b, avg_spectral);
+  }
 
   while (1) {
     for (; mask[0]; mask++, rgba+=4) {
-      uint32_t opa = mask[0];
-      weight += opa;
-      r      += opa*rgba[0]/(1<<15);
-      g      += opa*rgba[1]/(1<<15);
-      b      += opa*rgba[2]/(1<<15);
-      a      += opa*rgba[3]/(1<<15);
-
+      // sample at least one pixel but then only 1%
+      if (rand() % 100 != 0 && *sum_a > 0.0) {
+        continue;
+      }
+      float a = (float)mask[0] * rgba[3] / (1<<30);
+      float alpha_sums = a + *sum_a;
+      *sum_weight += (float)mask[0] / (1<<15);
+      float fac_a, fac_b;
+      fac_a = fac_b = 1.0f;
+      if (alpha_sums > 0.0f) {
+        fac_a = a / alpha_sums;
+        fac_b = 1.0 - fac_a;
+      }
+      if (paint > 0.0f) {
+        float spectral[10] = {0};
+        if (rgba[3] > 0) {
+          rgb_to_spectral((float)rgba[0] / rgba[3], (float)rgba[1] / rgba[3], (float)rgba[2] / rgba[3], spectral);
+          for (int i=0; i<10; i++) {
+            avg_spectral[i] = fastpow(spectral[i], fac_a) * fastpow(avg_spectral[i], fac_b);
+          }
+        }
+      }
+      if (paint < 1.0f) {
+        if (rgba[3] > 0) {
+          for (int i=0; i<3; i++) {
+            avg_rgb[i] = (float)rgba[i] * fac_a / rgba[3] + (float)avg_rgb[i] * fac_b;
+          }
+        }
+      }
+      *sum_a += a;
     }
+    float spec_rgb[3] = {0};
+    spectral_to_rgb(avg_spectral, spec_rgb);
+
+    *sum_r = spec_rgb[0] * paint + (1.0 - paint) * avg_rgb[0];
+    *sum_g = spec_rgb[1] * paint + (1.0 - paint) * avg_rgb[1];
+    *sum_b = spec_rgb[2] * paint + (1.0 - paint) * avg_rgb[2];
+
     if (!mask[1]) break;
     rgba += mask[1];
     mask += 2;
   }
-
-  // convert integer to float outside the performance critical loop
-  *sum_weight += weight;
-  *sum_r += r;
-  *sum_g += g;
-  *sum_b += b;
-  *sum_a += a;
 };
 
 

brushmodes.h

@@ -63,7 +63,8 @@ void get_color_pixels_accumulate (uint16_t * mask,
                                   float * sum_r,
                                   float * sum_g,
                                   float * sum_b,
-                                  float * sum_a
+                                  float * sum_a,
+                                  float paint
                                   );
 
 

mypaint-brush.c

@@ -828,7 +828,7 @@ mypaint_brush_set_state(MyPaintBrush *self, MyPaintBrushState i, float value)
         float smudge_radius = radius * fasterexp(self->settings_value[MYPAINT_BRUSH_SETTING_SMUDGE_RADIUS_LOG]);
         smudge_radius = CLAMP(smudge_radius, ACTUAL_RADIUS_MIN, ACTUAL_RADIUS_MAX);
 
-        mypaint_surface_get_color(surface, px, py, smudge_radius, &r, &g, &b, &a);
+        mypaint_surface_get_color(surface, px, py, smudge_radius, &r, &g, &b, &a, self->settings_value[MYPAINT_BRUSH_SETTING_PAINT_MODE]);
 
 
         //don't draw unless the picked-up alpha is above a certain level

mypaint-surface.c

@@ -49,11 +49,12 @@ void
 mypaint_surface_get_color(MyPaintSurface *self,
                         float x, float y,
                         float radius,
-                        float * color_r, float * color_g, float * color_b, float * color_a
+                        float * color_r, float * color_g, float * color_b, float * color_a,
+                        float paint
                         )
 {
     assert(self->get_color);
-    self->get_color(self, x, y, radius, color_r, color_g, color_b, color_a);
+    self->get_color(self, x, y, radius, color_r, color_g, color_b, color_a, paint);
 }
 
 
@@ -98,7 +99,7 @@ mypaint_surface_unref(MyPaintSurface *self)
 float mypaint_surface_get_alpha (MyPaintSurface *self, float x, float y, float radius)
 {
     float color_r, color_g, color_b, color_a;
-    mypaint_surface_get_color (self, x, y, radius, &color_r, &color_g, &color_b, &color_a);
+    mypaint_surface_get_color (self, x, y, radius, &color_r, &color_g, &color_b, &color_a, 1.0);
     return color_a;
 }
 

mypaint-surface.h

@@ -28,7 +28,8 @@ typedef struct MyPaintSurface MyPaintSurface;
 typedef void (*MyPaintSurfaceGetColorFunction) (MyPaintSurface *self,
                                                 float x, float y,
                                                 float radius,
-                                                float * color_r, float * color_g, float * color_b, float * color_a
+                                                float * color_r, float * color_g, float * color_b, float * color_a,
+                                                float paint
                                                 );
 
 typedef int (*MyPaintSurfaceDrawDabFunction) (MyPaintSurface *self,
@@ -93,7 +94,8 @@ void
 mypaint_surface_get_color(MyPaintSurface *self,
                         float x, float y,
                         float radius,
-                        float * color_r, float * color_g, float * color_b, float * color_a
+                        float * color_r, float * color_g, float * color_b, float * color_a,
+                        float paint
                         );
 
 

mypaint-tiled-surface.c

@@ -776,7 +776,8 @@ int draw_dab (MyPaintSurface *surface, float x, float y,
 
 void get_color (MyPaintSurface *surface, float x, float y,
                   float radius,
-                  float * color_r, float * color_g, float * color_b, float * color_a
+                  float * color_r, float * color_g, float * color_b, float * color_a,
+                  float paint
                   )
 {
     MyPaintTiledSurface *self = (MyPaintTiledSurface *)surface;
@@ -839,7 +840,7 @@ void get_color (MyPaintSurface *surface, float x, float y,
         #pragma omp critical
         {
         get_color_pixels_accumulate (mask, rgba_p,
-                                     &sum_weight, &sum_r, &sum_g, &sum_b, &sum_a);
+                                     &sum_weight, &sum_r, &sum_g, &sum_b, &sum_a, paint);
         }
 
         mypaint_tiled_surface_tile_request_end(self, &request_data);
@@ -848,16 +849,12 @@ void get_color (MyPaintSurface *surface, float x, float y,
 
     assert(sum_weight > 0.0f);
     sum_a /= sum_weight;
-    sum_r /= sum_weight;
-    sum_g /= sum_weight;
-    sum_b /= sum_weight;
-
     *color_a = sum_a;
     // now un-premultiply the alpha
     if (sum_a > 0.0f) {
-      *color_r = sum_r / sum_a;
-      *color_g = sum_g / sum_a;
-      *color_b = sum_b / sum_a;
+      *color_r = sum_r;
+      *color_g = sum_g;
+      *color_b = sum_b;
     } else {
       // it is all transparent, so don't care about the colors
       // (let's make them ugly so bugs will be visible)