From 0c8ca1380da7f81edf9c1e53f9486f5a5d4d43e8 Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@pobox.com>
Date: Fri, 24 Mar 2023 13:11:56 -0700
Subject: [PATCH] wip retooling some bits

better handling of reserved color
---
 dither-image.js | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/dither-image.js b/dither-image.js
index 422686c..618b884 100644
--- a/dither-image.js
+++ b/dither-image.js
@@ -617,8 +617,23 @@ function decimate(input, palette, n) {
             );
         });
         let topRanges = ranges.map((rgb) => Math.max(rgb.r, rgb.g, rgb.b));
-        let greatest = Math.max(...topRanges);
-        let index = topRanges.indexOf(greatest);
+        //let greatest = Math.max(...topRanges);
+        //let index = topRanges.indexOf(greatest);
+        let greatest = 0;
+        let index = -1;
+        for (let i = 0; i < topRanges.length; i++) {
+            if (topRanges[i] >= greatest) {
+                greatest = topRanges[i];
+                index = i;
+            }
+        }
+        if (index == -1) {
+            // We just ran out of colors! Pad the buckets.
+            while (buckets.length < n) {
+                buckets.push([new RGB(0, 0, 0)]);
+            }
+            break;
+        }
         let [lo, hi] = medianCut(buckets[index], ranges[index]);
         buckets.splice(index, 1, lo, hi);
     }