From 7867184985e7471b2bcf500196021730a0916d2e Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@pobox.com>
Date: Sat, 5 Nov 2022 19:22:59 -0700
Subject: [PATCH] tweaks

---
 dither4.js | 65 ++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 21 deletions(-)

diff --git a/dither4.js b/dither4.js
index 9d40627..00978fd 100644
--- a/dither4.js
+++ b/dither4.js
@@ -12,6 +12,27 @@ class RGB {
         return new RGB(r,g,b);
     }
 
+    cap() {
+        if (this.r < 0) {
+            this.r = 0;
+        }
+        if (this.g < 0) {
+            this.g = 0;
+        }
+        if (this.b < 0) {
+            this.b = 0;
+        }
+        if (this.r > 255) {
+            this.r = 255;
+        }
+        if (this.g > 255) {
+            this.g = 255;
+        }
+        if (this.b > 255) {
+            this.b = 255;
+        }
+    }
+
     add(other) {
         return new RGB(
             this.r + other.r,
@@ -335,14 +356,15 @@ function decimate(input, palette, n) {
         // Try dithering with this palette.
         for (let x = 0; x < line.length; x++) {
             let rgb = line[x];
-            rgb = rgb.difference(error.right);
+            rgb = rgb.add(error.right);
+            rgb.cap();
 
             // find the closest possible color
             let shortest = Infinity;
             let pick = -1;
 
             for (let i = 0; i < palette.length; i++) {
-                let diff = palette[i].difference(rgb);
+                let diff = rgb.difference(palette[i]);
                 let dist = diff.magnitude();
                 if (dist < shortest) {
                     nextError = diff;
@@ -361,19 +383,23 @@ function decimate(input, palette, n) {
             error.right.b = nextError.b;
             */
 
+            /*
             error.right.r = nextError.r / 2;
             error.right.g = nextError.g / 2;
             error.right.b = nextError.b / 2;
 
-            if (x == 0) {
-                error.red[x - 1] += nextError.r / 8;
-                error.green[x - 1] += nextError.g / 8;
-                error.blue[x - 1] += nextError.b / 8;
-            } else {
-                error.red[x] += nextError.r / 8;
-                error.green[x] += nextError.g / 8;
-                error.blue[x] += nextError.b / 8;
-            }
+            error.red[x + 1] += nextError.r / 2;
+            error.green[x + 1] += nextError.g / 2;
+            error.blue[x + 1] += nextError.b / 2;
+            */
+
+            error.right.r = nextError.r / 2;
+            error.right.g = nextError.g / 2;
+            error.right.b = nextError.b / 2;
+
+            error.red[x - 1] += nextError.r / 8;
+            error.green[x - 1] += nextError.g / 8;
+            error.blue[x - 1] += nextError.b / 8;
 
             error.red[x] += nextError.r / 4;
             error.green[x] += nextError.g / 4;
@@ -383,7 +409,7 @@ function decimate(input, palette, n) {
             error.green[x + 1] += nextError.g / 8;
             error.blue[x + 1] += nextError.b / 8;
 
-            fitness[x] = 1 / nextError.magnitude();
+            fitness[x] = 1 - (nextError.magnitude() / 442);
         }
         return {
             output,
@@ -407,13 +433,13 @@ function decimate(input, palette, n) {
                 continue; // keep black always
             }
             if (decimated[i].r == 255 && decimated[i].g == 255 && decimated[i].b == 255) {
-                //continue; // keep white always
+                continue; // keep white always
             }
             let coolFactor = popularity[i];
             /*
             for (let x = 0; x < line.length; x++) {
                 if (output[x] == i) {
-                    coolFactor *= fitness[i];
+                    coolFactor *= fitness[x];
                 }
             }
             */
@@ -475,13 +501,10 @@ function convert(source, sink) {
                 (line[x * 4 + 2] + line[x * 4 + 6]) / 2
             );
             if (nextError) {
-                rgb.r -= nextError.red[i];
-                rgb.g -= nextError.green[i];
-                rgb.b -= nextError.blue[i];
-            } else {
-                if (y > 0) {
-                    debugger;
-                }
+                rgb.r += nextError.red[i];
+                rgb.g += nextError.green[i];
+                rgb.b += nextError.blue[i];
+                rgb.cap();
             }
             input.push(rgb);
         }