From f5d7d2c71af3e70ca373864010aee981d6e6a1ea Mon Sep 17 00:00:00 2001
From: Brian Popow <popow@gmx.de>
Date: Wed, 12 Aug 2020 11:21:58 +0200
Subject: [PATCH] Remove empty histograms

---
 src/ImageSharp/Formats/WebP/Lossless/HistogramEncoder.cs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/ImageSharp/Formats/WebP/Lossless/HistogramEncoder.cs b/src/ImageSharp/Formats/WebP/Lossless/HistogramEncoder.cs
index 324a2848b4..a1ca4108ab 100644
--- a/src/ImageSharp/Formats/WebP/Lossless/HistogramEncoder.cs
+++ b/src/ImageSharp/Formats/WebP/Lossless/HistogramEncoder.cs
@@ -68,9 +68,11 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossless
 
             // Cubic ramp between 1 and MaxHistoGreedy:
             int thresholdSize = (int)(1 + (x * x * x * (MaxHistoGreedy - 1)));
+            RemoveEmptyHistograms(imageHisto);
             bool doGreedy = HistogramCombineStochastic(imageHisto, thresholdSize);
             if (doGreedy)
             {
+                RemoveEmptyHistograms(imageHisto);
                 HistogramCombineGreedy(imageHisto);
             }