From 9826a90e02ebc5e53aea00af1e91e2b91004d1f5 Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@pobox.com>
Date: Sun, 19 Mar 2023 18:22:33 -0700
Subject: [PATCH] some oldbits

---
 dither-image.js | 71 +++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 60 insertions(+), 11 deletions(-)

diff --git a/dither-image.js b/dither-image.js
index 3b0aec4..5b2756b 100644
--- a/dither-image.js
+++ b/dither-image.js
@@ -426,7 +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(palette.length);
+        let fitness = new Float64Array(width);
         let error = {
             cur: [],
             next: [],
@@ -476,10 +476,12 @@ function decimate(input, palette, n, inputError, y) {
 
             let mag = nextError.magnitude();
             fitness[x] = maxDist / mag;
+            // 442 is the 3d distance across the rgb cube
+            //fitness[x] = 442 - (nextError.magnitude());
+            //fitness[x] = 442 / (442 - nextError.magnitude());
+            fitness[x] = 255 / (256 - Math.max(0, nextError.r, nextError.g, nextError.b));
 
-            // just store the distance2
             let mag2 = nextError.magnitude2();
-            //fitness[x] = mag2;
             distance2 += mag2;
         }
         return {
@@ -509,11 +511,12 @@ function decimate(input, palette, n, inputError, y) {
     //reserved = [0, 5, 10, 15]; // grayscale
     //reserved = [0, 0x48, 0x78, 15]; // vaporwave
     //reserved = [0, 0x3c, 0x78, 15]; // red/blue/white
+
     /*
     if (( y & 1 ) === 0) {
-        reserved = [0, 0x3c, 0x1a, 15]; // red/yellow/white
+        reserved = [0, 0x3c, 0x1e, 15]; // red/yellow/white
     } else {
-        reserved = [0, 0x76, 0x9a, 15]; // blue/cyan/white
+        reserved = [0, 0x76, 0x9e, 0xb8]; // blue/cyan/green
     }
     */
 
@@ -553,7 +556,8 @@ function decimate(input, palette, n, inputError, y) {
         a = a.sort((a, b) => b.count - a.count);
         a = a.map(({hue}) => hue);
         a = a.filter((color) => !keepers[color]);
-        a = a.slice(0, n - reserved.length);
+        //a = a.slice(0, n - reserved.length);
+        a = a.slice(0, decimated.length - 1 - reserved.length);
         a = a.map((hue) => (hue << 4) | lumas[hue]);
         a = a.sort((a, b) => a - b);
 
@@ -564,20 +568,64 @@ function decimate(input, palette, n, inputError, y) {
 
     // 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 {popularity} = dither(decimated);
         let a = decimated;
+        // temporarily strip the reserved items
         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);
+        decimated = a.slice(0, n);
         //console.log(decimated);
     }
     //console.log('end', decimated);
-    
+    */
+
+    while (decimated.length > n) {
+        let {popularity, fitness, output} = dither(decimated);
+
+        // Try dropping least used color on each iteration
+        let least = Infinity;
+        let pick = -1;
+        for (let i = 1; i < decimated.length; i++) {
+
+            //let coolFactor = popularity[i];
+
+            let coolFactor = 0;
+            if (popularity[i]) {
+                for (let x = 0; x < width; x++) {
+                    if (output[x] == i) {
+                        // Scale up the scoring for close matches to prioritize
+                        // color accuracy over raw linear usage.
+                        //coolFactor += (fitness[x] ** 2);
+                        coolFactor += (fitness[x] ** 4);
+                    }
+                }
+            }
+            if (coolFactor < least) {
+                pick = i;
+                least = coolFactor;
+            }
+            decimated = decimated.filter((color, i) => {
+                if (i == 0) {
+                    return true;
+                }
+                if (i == pick) {
+                    return false;
+                }
+                // Also drop any non-black unused colors to save trouble.
+                // However -- this may change dither results.
+                // Try this with/without later.
+                if (popularity[i] == 0) {
+                    return false;
+                }
+                return true;
+            });
+        }
+    }
+                                                    
     // Palette fits
     return dither(decimated);
 }
@@ -845,6 +893,7 @@ async function saveImage(width, height, lines, dest) {
             resolve(image);
         });
     });
+    await image.resize(Math.round(width2 * 2 / 1.2), height * 2);
     await image.writeAsync(dest);
 }