1 files changed, 127 insertions, 0 deletions
diff --git a/iconloaderlib/src/com/android/launcher3/icons/ColorExtractor.java b/iconloaderlib/src/com/android/launcher3/icons/ColorExtractor.java
new file mode 100644
index 000000000..87bda825c
--- /dev/null
+++ b/iconloaderlib/src/com/android/launcher3/icons/ColorExtractor.java
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.launcher3.icons;
+
+import android.graphics.Bitmap;
+import android.graphics.Color;
+import android.util.SparseArray;
+import java.util.Arrays;
+
+/**
+ * Utility class for extracting colors from a bitmap.
+ */
+public class ColorExtractor {
+
+    private final int NUM_SAMPLES = 20;
+    private final float[] mTmpHsv = new float[3];
+    private final float[] mTmpHueScoreHistogram = new float[360];
+    private final int[] mTmpPixels = new int[NUM_SAMPLES];
+    private final SparseArray<Float> mTmpRgbScores = new SparseArray<>();
+
+    /**
+     * This picks a dominant color, looking for high-saturation, high-value, repeated hues.
+     * @param bitmap The bitmap to scan
+     */
+    public int findDominantColorByHue(Bitmap bitmap) {
+        return findDominantColorByHue(bitmap, NUM_SAMPLES);
+    }
+
+    /**
+     * This picks a dominant color, looking for high-saturation, high-value, repeated hues.
+     * @param bitmap The bitmap to scan
+     */
+    public int findDominantColorByHue(Bitmap bitmap, int samples) {
+        final int height = bitmap.getHeight();
+        final int width = bitmap.getWidth();
+        int sampleStride = (int) Math.sqrt((height * width) / samples);
+        if (sampleStride < 1) {
+            sampleStride = 1;
+        }
+
+        // This is an out-param, for getting the hsv values for an rgb
+        float[] hsv = mTmpHsv;
+        Arrays.fill(hsv, 0);
+
+        // First get the best hue, by creating a histogram over 360 hue buckets,
+        // where each pixel contributes a score weighted by saturation, value, and alpha.
+        float[] hueScoreHistogram = mTmpHueScoreHistogram;
+        Arrays.fill(hueScoreHistogram, 0);
+        float highScore = -1;
+        int bestHue = -1;
+
+        int[] pixels = mTmpPixels;
+        Arrays.fill(pixels, 0);
+        int pixelCount = 0;
+
+        for (int y = 0; y < height; y += sampleStride) {
+            for (int x = 0; x < width; x += sampleStride) {
+                int argb = bitmap.getPixel(x, y);
+                int alpha = 0xFF & (argb >> 24);
+                if (alpha < 0x80) {
+                    // Drop mostly-transparent pixels.
+                    continue;
+                }
+                // Remove the alpha channel.
+                int rgb = argb | 0xFF000000;
+                Color.colorToHSV(rgb, hsv);
+                // Bucket colors by the 360 integer hues.
+                int hue = (int) hsv[0];
+                if (hue < 0 || hue >= hueScoreHistogram.length) {
+                    // Defensively avoid array bounds violations.
+                    continue;
+                }
+                if (pixelCount < samples) {
+                    pixels[pixelCount++] = rgb;
+                }
+                float score = hsv[1] * hsv[2];
+                hueScoreHistogram[hue] += score;
+                if (hueScoreHistogram[hue] > highScore) {
+                    highScore = hueScoreHistogram[hue];
+                    bestHue = hue;
+                }
+            }
+        }
+
+        SparseArray<Float> rgbScores = mTmpRgbScores;
+        rgbScores.clear();
+        int bestColor = 0xff000000;
+        highScore = -1;
+        // Go back over the RGB colors that match the winning hue,
+        // creating a histogram of weighted s*v scores, for up to 100*100 [s,v] buckets.
+        // The highest-scoring RGB color wins.
+        for (int i = 0; i < pixelCount; i++) {
+            int rgb = pixels[i];
+            Color.colorToHSV(rgb, hsv);
+            int hue = (int) hsv[0];
+            if (hue == bestHue) {
+                float s = hsv[1];
+                float v = hsv[2];
+                int bucket = (int) (s * 100) + (int) (v * 10000);
+                // Score by cumulative saturation * value.
+                float score = s * v;
+                Float oldTotal = rgbScores.get(bucket);
+                float newTotal = oldTotal == null ? score : oldTotal + score;
+                rgbScores.put(bucket, newTotal);
+                if (newTotal > highScore) {
+                    highScore = newTotal;
+                    // All the colors in the winning bucket are very similar. Last in wins.
+                    bestColor = rgb;
+                }
+            }
+        }
+        return bestColor;
+    }
+}