From 9a93e7341faf7b3d1973482d1d90d29fd0d7f050 Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@pobox.com>
Date: Sun, 19 Mar 2023 16:56:18 -0700
Subject: [PATCH] wip almost

---
 dither-image.js | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/dither-image.js b/dither-image.js
index 0157f2b..3b0aec4 100644
--- a/dither-image.js
+++ b/dither-image.js
@@ -110,6 +110,10 @@ class RGB {
         );
     }
 
+    magnitude() {
+        return Math.sqrt(this.magnitude2());
+    }
+
     magnitude2() {
         return this.r * this.r +
             this.g * this.g +
@@ -117,6 +121,8 @@ class RGB {
     }
 }
 
+const maxDist = (new RGB(255, 255, 255)).magnitude();
+
 // snarfed from https://lospec.com/palette-list/atari-8-bit-family-gtia
 // which was calculated with Retrospecs App's Atari 800 emulator
 let atariRGB = [
@@ -420,7 +426,7 @@ function decimate(input, palette, n, inputError, y) {
 
     // Apply dithering with given palette and collect color usage stats
     let dither = (palette) => {
-        let fitness = new Float64Array(width);
+        let fitness = new Float64Array(palette.length);
         let error = {
             cur: [],
             next: [],
@@ -431,7 +437,7 @@ function decimate(input, palette, n, inputError, y) {
         }
 
         let output = new Uint8Array(width);
-        let popularity = new Int32Array(width);
+        let popularity = new Int32Array(palette.length);
         let distance2 = 0;
 
         let nextError = new RGB(0, 0, 0);
@@ -468,9 +474,12 @@ function decimate(input, palette, n, inputError, y) {
             error.next[x]?.inc(double);
             error.next[x + 1]?.inc(double);
 
+            let mag = nextError.magnitude();
+            fitness[x] = maxDist / mag;
+
             // just store the distance2
             let mag2 = nextError.magnitude2();
-            fitness[x] = mag2;
+            //fitness[x] = mag2;
             distance2 += mag2;
         }
         return {
@@ -521,6 +530,9 @@ function decimate(input, palette, n, inputError, y) {
         return arr;
     };
 
+    // this takes the top hues, and uses the brightest of each hue
+    // needs tuning
+    /*
     // first, dither to the total atari palette
     while (decimated.length > n) {
         let {popularity} = dither(decimated);
@@ -548,7 +560,24 @@ function decimate(input, palette, n, inputError, y) {
         decimated = reserved.concat(a);
     }
     console.log('end', decimated);
+    */
 
+    // popularity? not really working right
+    // first, dither to the total atari palette
+    while (decimated.length > n) {
+        let {popularity, fitness} = dither(decimated);
+        // temporarily strip the reserved items
+        //console.log(y);
+        let a = decimated;
+        a = a.filter((color) => !keepers[color]);
+        a = a.sort((a, b) => popularity[b] - popularity[a]);
+        //a = a.slice(0, n - reserved.length);
+        a = reserved.concat(a);
+        decimated = a.slice(0, decimated.length - 1);
+        //console.log(decimated);
+    }
+    //console.log('end', decimated);
+    
     // Palette fits
     return dither(decimated);
 }