[Vector] Changed the gradient resolution algorithm to average out the…

… colours.
parasol-framework · Feb 2, 2025 · e6ac0d3 · e6ac0d3
1 parent 4ed5787
commit e6ac0d3
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Showing 2 changed files with 22 additions and 17 deletions.
diff --git a/src/vector/defs/gradient.cpp b/src/vector/defs/gradient.cpp
@@ -142,19 +142,10 @@ GradientColours::GradientColours(const std::array<FRGB, 256> &Map, double Resolu
 {
    resolution = Resolution;
 
-   if (resolution > 0) {  // Select every nth colour from the map.
-      auto current = agg::rgba8(Map[0]);
-      LONG in = F2T(resolution * 255.0);
-      for (LONG i = 0; i < std::ssize(Map); i++, in--) {
-         if ((!in) and (i != std::ssize(Map)-1)) { current = agg::rgba8(Map[i]); in = F2T(resolution * 255.0); }
-         table[i] = current;
-      }
-   }
-   else {
-      for (LONG i=0; i < std::ssize(Map); i++) {
-         table[i] = agg::rgba8(Map[i]);
-      }
+   for (LONG i=0; i < std::ssize(Map); i++) {
+      table[i] = agg::rgba8(Map[i]);
    }
+   if (Resolution > 0) apply_resolution(Resolution);
 }
 
 //********************************************************************************************************************

diff --git a/src/vector/vector.h b/src/vector/vector.h
@@ -534,11 +534,25 @@ class GradientColours {
 
       void apply_resolution(double Resolution) {
          resolution = Resolution;
-         auto current = table[0];
-         LONG in = F2T(resolution * 255.0);
-         for (LONG i = 0; i < 256; i++, in--) {
-            if ((!in) and (i != 255)) { current = table[i]; in = F2T(resolution * 255.0); }
-            table[i] = current;
+
+         // For a given block of colours, compute the average colour and apply it to the entire block.
+
+         LONG block_size = F2T(resolution * table.size());
+         for (LONG i = 0; i < table.size(); i += block_size) {
+
+            LONG red = 0, green = 0, blue = 0, alpha = 0, total = 0;
+            for (LONG b=i; (b < i + block_size) and (b < table.size()); b++, total++) {
+               red   += table[b].r * table[b].r;
+               green += table[b].g * table[b].g;
+               blue  += table[b].b * table[b].b;
+               alpha += table[b].a * table[b].a;
+            }
+
+            auto col = agg::rgba8{ 
+               UBYTE(sqrt(red/total)), UBYTE(sqrt(green/total)), UBYTE(sqrt(blue/total)), UBYTE(sqrt(alpha/total)) 
+            };
+
+            for (LONG b = i; (b < i + block_size) and (b < table.size()); b++) table[b] = col;
          }
       }
 };