From b4e3394809be3a4e181d5929c2bc02430eb42bef Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@pobox.com>
Date: Tue, 21 Mar 2023 18:34:14 -0700
Subject: [PATCH] yes yes hahaha yes

---
 dither-image.js | 47 +++++++++++++++++++++++++++--------------------
 1 file changed, 27 insertions(+), 20 deletions(-)

diff --git a/dither-image.js b/dither-image.js
index a0eda76..f2f7af9 100644
--- a/dither-image.js
+++ b/dither-image.js
@@ -407,11 +407,10 @@ let atariRGB = [
  * @param {RGB[]} input source scanline data, in linear RGB
  * @param {number[]} palette - current working palette, as Atari 8-bit color values (low nybble luminance, high nybble hue)
  * @param {number} n - target color count
- * @param {RGB[]} inputError
  * @param {number} y
  * @returns {{output: number[], palette: number[], error: RGB[]}}
  */
-function decimate(input, palette, n, inputError, y) {
+function decimate(input, palette, n) {
     // to brute-force, the possible palettes are:
     // 255 * 254 * 253 = 16,386,810
     //
@@ -433,9 +432,6 @@ function decimate(input, palette, n, inputError, y) {
         if (error) {
             rgb.inc(error.cur[x]);
         }
-        if (inputError) {
-            rgb.inc(inputError[x]);
-        }
         rgb.cap();
         return rgb;
     };
@@ -540,9 +536,9 @@ function decimate(input, palette, n, inputError, y) {
 
     // Median cut!
     // https://en.wikipedia.org/wiki/Median_cut
-    //let buckets = [input.slice()];
-    let initial = dither(palette);
-    let buckets = [initial.output.map((i) => atariRGB[palette[i]])];
+    let buckets = [input.slice()];
+    //let initial = dither(palette);
+    //let buckets = [initial.output.map((i) => atariRGB[palette[i]])];
     let medianCut = (bucket, range) => {
         if (bucket.length < 2) {
             console.log(bucket);
@@ -582,19 +578,25 @@ function decimate(input, palette, n, inputError, y) {
     }
     decimated = buckets.map((bucket) => {
         // Average the RGB colors in this chunk
-        //let rgb = bucket
-        //    .reduce((acc, rgb) => acc.inc(rgb), new RGB(0, 0, 0))
-        //    .divide(bucket.length);
-        
-        // scale to the max luma
+        let rgb = bucket
+            .reduce((acc, rgb) => acc.inc(rgb), new RGB(0, 0, 0))
+            .divide(bucket.length);
+
+        let avg_luma = rgb.luma();
+        let lumas = bucket.map((rgb) => rgb.luma());
+        let brightest = Math.max(...lumas);
+        if (avg_luma > 0) {
+            rgb = rgb.multiply(brightest / avg_luma);
+        }
+
+    
+        // pick the luma-brightest color in the bucket
         // kinda nice but really aggressive with the colors
+        /*
         let lumas = bucket.map((rgb) => rgb.luma());
         let luma = Math.max(...lumas);
         let rgb = bucket[lumas.indexOf(luma)];
-        let from = rgb.luma();
-        if (from > 0) {
-            rgb = rgb.multiply(luma / rgb.luma());
-        }
+        */
 
         // Take the channel-brightest color in the bucket
         // bad
@@ -615,6 +617,7 @@ function decimate(input, palette, n, inputError, y) {
             Math.max(...bucket.map((rgb) => rgb.b))
         );
         */
+
         // combine the median of each channel
         // sux
         /*
@@ -734,9 +737,13 @@ async function convert(source) {
 
     let lines = [];
     for (let y = 0; y < height; y++) {
-        let error = lines[y - 1]?.error;
-        let inputLine = input.slice(y * width, (y + 1) * width);
-        let line = decimate(inputLine, allColors, 4, error, y);
+        let inputLine = input
+            .slice(y * width, (y + 1) * width);
+        if (y > 0) {
+            let error = lines[y - 1].error;
+            inputLine = inputLine.map((rgb, x) => RGB.add(rgb, error[x]));
+        }
+        let line = decimate(inputLine, allColors, 4, y);
         lines.push(line);
     }
     return {