1 // Copyright 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 package org.chromium.ui.gfx; 6 7 import android.content.res.Resources; 8 import android.graphics.Bitmap; 9 import android.graphics.BitmapFactory; 10 11 import org.chromium.base.CalledByNative; 12 import org.chromium.base.JNINamespace; 13 14 /** 15 * Helper class to decode and sample down bitmap resources. 16 */ 17 @JNINamespace("gfx") 18 public class BitmapHelper { 19 @CalledByNative createBitmap(int width, int height, int bitmapFormatValue)20 private static Bitmap createBitmap(int width, 21 int height, 22 int bitmapFormatValue) { 23 Bitmap.Config bitmapConfig = getBitmapConfigForFormat(bitmapFormatValue); 24 return Bitmap.createBitmap(width, height, bitmapConfig); 25 } 26 27 /** 28 * Decode and sample down a bitmap resource to the requested width and height. 29 * 30 * @param name The resource name of the bitmap to decode. 31 * @param reqWidth The requested width of the resulting bitmap. 32 * @param reqHeight The requested height of the resulting bitmap. 33 * @return A bitmap sampled down from the original with the same aspect ratio and dimensions. 34 * that are equal to or greater than the requested width and height. 35 */ 36 @CalledByNative decodeDrawableResource(String name, int reqWidth, int reqHeight)37 private static Bitmap decodeDrawableResource(String name, 38 int reqWidth, 39 int reqHeight) { 40 Resources res = Resources.getSystem(); 41 int resId = res.getIdentifier(name, null, null); 42 if (resId == 0) return null; 43 44 final BitmapFactory.Options options = new BitmapFactory.Options(); 45 options.inJustDecodeBounds = true; 46 BitmapFactory.decodeResource(res, resId, options); 47 48 options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight); 49 options.inJustDecodeBounds = false; 50 options.inPreferredConfig = Bitmap.Config.ARGB_8888; 51 return BitmapFactory.decodeResource(res, resId, options); 52 } 53 54 // http://developer.android.com/training/displaying-bitmaps/load-bitmap.html calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight)55 private static int calculateInSampleSize(BitmapFactory.Options options, 56 int reqWidth, 57 int reqHeight) { 58 // Raw height and width of image 59 final int height = options.outHeight; 60 final int width = options.outWidth; 61 int inSampleSize = 1; 62 63 if (height > reqHeight || width > reqWidth) { 64 65 // Calculate ratios of height and width to requested height and width 66 final int heightRatio = Math.round((float) height / (float) reqHeight); 67 final int widthRatio = Math.round((float) width / (float) reqWidth); 68 69 // Choose the smallest ratio as inSampleSize value, this will guarantee 70 // a final image with both dimensions larger than or equal to the 71 // requested height and width. 72 inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio; 73 } 74 75 return inSampleSize; 76 } 77 78 /** 79 * Provides a matching integer constant for the Bitmap.Config value passed. 80 * 81 * @param bitmapConfig The Bitmap Configuration value. 82 * @return Matching integer constant for the Bitmap.Config value passed. 83 */ 84 @CalledByNative 85 private static int getBitmapFormatForConfig(Bitmap.Config bitmapConfig) { 86 switch (bitmapConfig) { 87 case ALPHA_8: 88 return BitmapFormat.FORMAT_ALPHA_8; 89 case ARGB_4444: 90 return BitmapFormat.FORMAT_ARGB_4444; 91 case ARGB_8888: 92 return BitmapFormat.FORMAT_ARGB_8888; 93 case RGB_565: 94 return BitmapFormat.FORMAT_RGB_565; 95 default: 96 return BitmapFormat.FORMAT_NO_CONFIG; 97 } 98 } 99 100 /** 101 * Provides a matching Bitmap.Config for the enum config value passed. 102 * 103 * @param bitmapFormatValue The Bitmap Configuration enum value. 104 * @return Matching Bitmap.Config for the enum value passed. 105 */ 106 private static Bitmap.Config getBitmapConfigForFormat(int bitmapFormatValue) { 107 switch (bitmapFormatValue) { 108 case BitmapFormat.FORMAT_ALPHA_8: 109 return Bitmap.Config.ALPHA_8; 110 case BitmapFormat.FORMAT_ARGB_4444: 111 return Bitmap.Config.ARGB_4444; 112 case BitmapFormat.FORMAT_RGB_565: 113 return Bitmap.Config.RGB_565; 114 case BitmapFormat.FORMAT_ARGB_8888: 115 default: 116 return Bitmap.Config.ARGB_8888; 117 } 118 } 119 120 } 121