1 /*
2  * Copyright (C) 2014 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License
15  */
16 
17 package com.android.internal.util;
18 
19 import android.graphics.Bitmap;
20 import android.graphics.Bitmap.Config;
21 import android.graphics.Canvas;
22 import android.graphics.Matrix;
23 import android.graphics.Paint;
24 import android.graphics.PorterDuff;
25 import android.graphics.drawable.BitmapDrawable;
26 import android.graphics.drawable.Drawable;
27 
28 /**
29  * Utility class for image analysis and processing.
30  *
31  * @hide
32  */
33 public class ImageUtils {
34 
35     // Amount (max is 255) that two channels can differ before the color is no longer "gray".
36     private static final int TOLERANCE = 20;
37 
38     // Alpha amount for which values below are considered transparent.
39     private static final int ALPHA_TOLERANCE = 50;
40 
41     // Size of the smaller bitmap we're actually going to scan.
42     private static final int COMPACT_BITMAP_SIZE = 64; // pixels
43 
44     private int[] mTempBuffer;
45     private Bitmap mTempCompactBitmap;
46     private Canvas mTempCompactBitmapCanvas;
47     private Paint mTempCompactBitmapPaint;
48     private final Matrix mTempMatrix = new Matrix();
49 
50     /**
51      * Checks whether a bitmap is grayscale. Grayscale here means "very close to a perfect
52      * gray".
53      *
54      * Instead of scanning every pixel in the bitmap, we first resize the bitmap to no more than
55      * COMPACT_BITMAP_SIZE^2 pixels using filtering. The hope is that any non-gray color elements
56      * will survive the squeezing process, contaminating the result with color.
57      */
isGrayscale(Bitmap bitmap)58     public boolean isGrayscale(Bitmap bitmap) {
59         int height = bitmap.getHeight();
60         int width = bitmap.getWidth();
61 
62         // shrink to a more manageable (yet hopefully no more or less colorful) size
63         if (height > COMPACT_BITMAP_SIZE || width > COMPACT_BITMAP_SIZE) {
64             if (mTempCompactBitmap == null) {
65                 mTempCompactBitmap = Bitmap.createBitmap(
66                         COMPACT_BITMAP_SIZE, COMPACT_BITMAP_SIZE, Bitmap.Config.ARGB_8888
67                 );
68                 mTempCompactBitmapCanvas = new Canvas(mTempCompactBitmap);
69                 mTempCompactBitmapPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
70                 mTempCompactBitmapPaint.setFilterBitmap(true);
71             }
72             mTempMatrix.reset();
73             mTempMatrix.setScale(
74                     (float) COMPACT_BITMAP_SIZE / width,
75                     (float) COMPACT_BITMAP_SIZE / height,
76                     0, 0);
77             mTempCompactBitmapCanvas.drawColor(0, PorterDuff.Mode.SRC); // select all, erase
78             mTempCompactBitmapCanvas.drawBitmap(bitmap, mTempMatrix, mTempCompactBitmapPaint);
79             bitmap = mTempCompactBitmap;
80             width = height = COMPACT_BITMAP_SIZE;
81         }
82 
83         final int size = height*width;
84         ensureBufferSize(size);
85         bitmap.getPixels(mTempBuffer, 0, width, 0, 0, width, height);
86         for (int i = 0; i < size; i++) {
87             if (!isGrayscale(mTempBuffer[i])) {
88                 return false;
89             }
90         }
91         return true;
92     }
93 
94     /**
95      * Makes sure that {@code mTempBuffer} has at least length {@code size}.
96      */
ensureBufferSize(int size)97     private void ensureBufferSize(int size) {
98         if (mTempBuffer == null || mTempBuffer.length < size) {
99             mTempBuffer = new int[size];
100         }
101     }
102 
103     /**
104      * Classifies a color as grayscale or not. Grayscale here means "very close to a perfect
105      * gray"; if all three channels are approximately equal, this will return true.
106      *
107      * Note that really transparent colors are always grayscale.
108      */
isGrayscale(int color)109     public static boolean isGrayscale(int color) {
110         int alpha = 0xFF & (color >> 24);
111         if (alpha < ALPHA_TOLERANCE) {
112             return true;
113         }
114 
115         int r = 0xFF & (color >> 16);
116         int g = 0xFF & (color >> 8);
117         int b = 0xFF & color;
118 
119         return Math.abs(r - g) < TOLERANCE
120                 && Math.abs(r - b) < TOLERANCE
121                 && Math.abs(g - b) < TOLERANCE;
122     }
123 
124     /**
125      * Convert a drawable to a bitmap, scaled to fit within maxWidth and maxHeight.
126      */
buildScaledBitmap(Drawable drawable, int maxWidth, int maxHeight)127     public static Bitmap buildScaledBitmap(Drawable drawable, int maxWidth,
128             int maxHeight) {
129         if (drawable == null) {
130             return null;
131         }
132         int originalWidth = drawable.getIntrinsicWidth();
133         int originalHeight = drawable.getIntrinsicHeight();
134 
135         if ((originalWidth <= maxWidth) && (originalHeight <= maxHeight) &&
136                 (drawable instanceof BitmapDrawable)) {
137             return ((BitmapDrawable) drawable).getBitmap();
138         }
139         if (originalHeight <= 0 || originalWidth <= 0) {
140             return null;
141         }
142 
143         // create a new bitmap, scaling down to fit the max dimensions of
144         // a large notification icon if necessary
145         float ratio = Math.min((float) maxWidth / (float) originalWidth,
146                 (float) maxHeight / (float) originalHeight);
147         ratio = Math.min(1.0f, ratio);
148         int scaledWidth = (int) (ratio * originalWidth);
149         int scaledHeight = (int) (ratio * originalHeight);
150         Bitmap result = Bitmap.createBitmap(scaledWidth, scaledHeight, Config.ARGB_8888);
151 
152         // and paint our app bitmap on it
153         Canvas canvas = new Canvas(result);
154         drawable.setBounds(0, 0, scaledWidth, scaledHeight);
155         drawable.draw(canvas);
156 
157         return result;
158     }
159 }
160