1 /* 2 * Copyright (C) 2012 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.contacts.common.util; 18 19 import android.graphics.Bitmap; 20 import android.graphics.BitmapFactory; 21 22 /** 23 * Provides static functions to decode bitmaps at the optimal size 24 */ 25 public class BitmapUtil { BitmapUtil()26 private BitmapUtil() {} 27 28 /** 29 * Returns Width or Height of the picture, depending on which size is smaller. Doesn't actually 30 * decode the picture, so it is pretty efficient to run. 31 */ getSmallerExtentFromBytes(byte[] bytes)32 public static int getSmallerExtentFromBytes(byte[] bytes) { 33 final BitmapFactory.Options options = new BitmapFactory.Options(); 34 35 // don't actually decode the picture, just return its bounds 36 options.inJustDecodeBounds = true; 37 BitmapFactory.decodeByteArray(bytes, 0, bytes.length, options); 38 39 // test what the best sample size is 40 return Math.min(options.outWidth, options.outHeight); 41 } 42 43 /** 44 * Finds the optimal sampleSize for loading the picture 45 * @param originalSmallerExtent Width or height of the picture, whichever is smaller 46 * @param targetExtent Width or height of the target view, whichever is bigger. 47 * 48 * If either one of the parameters is 0 or smaller, no sampling is applied 49 */ findOptimalSampleSize(int originalSmallerExtent, int targetExtent)50 public static int findOptimalSampleSize(int originalSmallerExtent, int targetExtent) { 51 // If we don't know sizes, we can't do sampling. 52 if (targetExtent < 1) return 1; 53 if (originalSmallerExtent < 1) return 1; 54 55 // Test what the best sample size is. To do that, we find the sample size that gives us 56 // the best trade-off between resulting image size and memory requirement. We allow 57 // the down-sampled image to be 20% smaller than the target size. That way we can get around 58 // unfortunate cases where e.g. a 720 picture is requested for 362 and not down-sampled at 59 // all. Why 20%? Why not. Prove me wrong. 60 int extent = originalSmallerExtent; 61 int sampleSize = 1; 62 while ((extent >> 1) >= targetExtent * 0.8f) { 63 sampleSize <<= 1; 64 extent >>= 1; 65 } 66 67 return sampleSize; 68 } 69 70 /** 71 * Decodes the bitmap with the given sample size 72 */ decodeBitmapFromBytes(byte[] bytes, int sampleSize)73 public static Bitmap decodeBitmapFromBytes(byte[] bytes, int sampleSize) { 74 final BitmapFactory.Options options; 75 if (sampleSize <= 1) { 76 options = null; 77 } else { 78 options = new BitmapFactory.Options(); 79 options.inSampleSize = sampleSize; 80 } 81 return BitmapFactory.decodeByteArray(bytes, 0, bytes.length, options); 82 } 83 } 84