From 1439c86ff54664012c4a30288518671aba1d7176 Mon Sep 17 00:00:00 2001 From: Aurélien Pomini Date: Thu, 27 Apr 2023 15:12:55 +0000 Subject: Use less clusters for color extraction for small bitmaps The color extraction in WallpaperColors uses a K-Mean algorithm. Currently, it uses 128 clusters, so it generates 128 colors, and then select the most important ones. But for most widgets this method is called with highly downscaled bitmaps (as small as 20x20 px), so we're trying to k-mean 128 clusters with only a couple hundreds of datapoints, which is most likely instable. This CL changes the number of cluster to be max(5, min(nPixels / 16, 128)). Thus, image with less than 2048 px (about 45x45) will use less than 128 clusters, but always at least 5 clusters. Bug: 273505854 Bug: 268180548 Test: perfetto trace Test: manual: observe the result on widget colors Change-Id: I34c13cfca392bb64bae4e7bf0adc1933c0eeb67c --- core/java/android/app/WallpaperColors.java | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/core/java/android/app/WallpaperColors.java b/core/java/android/app/WallpaperColors.java index a34a50c4b7b0..be1d8b8ad7d3 100644 --- a/core/java/android/app/WallpaperColors.java +++ b/core/java/android/app/WallpaperColors.java @@ -213,9 +213,17 @@ public final class WallpaperColors implements Parcelable { .resizeBitmapArea(MAX_WALLPAPER_EXTRACTION_AREA) .generate(); } else { + // in any case, always use between 5 and 128 clusters + int minClusters = 5; + int maxClusters = 128; + + // if the bitmap is very small, use bitmapArea/16 clusters instead of 128 + int minPixelsPerCluster = 16; + int numberOfColors = Math.max(minClusters, + Math.min(maxClusters, bitmapArea / minPixelsPerCluster)); palette = Palette .from(bitmap, new CelebiQuantizer()) - .maximumColorCount(128) + .maximumColorCount(numberOfColors) .resizeBitmapArea(MAX_WALLPAPER_EXTRACTION_AREA) .generate(); } -- cgit v1.2.3-59-g8ed1b