src/com/owncloud/android/utils/BitmapUtils.java

   1 /* ownCloud Android client application
   2  *   Copyright (C) 2012-2014 ownCloud Inc.
   3  *
   4  *   This program is free software: you can redistribute it and/or modify
   5  *   it under the terms of the GNU General Public License version 2,
   6  *   as published by the Free Software Foundation.
   7  *
   8  *   This program is distributed in the hope that it will be useful,
   9  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  *   GNU General Public License for more details.
  12  *
  13  *   You should have received a copy of the GNU General Public License
  14  *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15  *
  16  */
  17 package com.owncloud.android.utils;
  18
  19 import android.graphics.Bitmap;
  20 import android.graphics.BitmapFactory;
  21 import android.graphics.BitmapFactory.Options;
  22
  23 /**
  24  * Utility class with methods for decoding Bitmaps.
  25  *
  26  * @author David A. Velasco
  27  */
  28 public class BitmapUtils {
  29
  30
  31     /**
  32      * Decodes a bitmap from a file containing it minimizing the memory use, known that the bitmap
  33      * will be drawn in a surface of reqWidth x reqHeight
  34      *
  35      * @param srcPath       Absolute path to the file containing the image.
  36      * @param reqWidth      Width of the surface where the Bitmap will be drawn on, in pixels.
  37      * @param reqHeight     Height of the surface where the Bitmap will be drawn on, in pixels.
  38      * @return
  39      */
  40     public static Bitmap decodeSampledBitmapFromFile(String srcPath, int reqWidth, int reqHeight) {
  41
  42         // set desired options that will affect the size of the bitmap
  43         final Options options = new Options();
  44         options.inScaled = true;
  45         options.inPurgeable = true;
  46         if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.GINGERBREAD_MR1) {
  47             options.inPreferQualityOverSpeed = false;
  48         }
  49         if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.HONEYCOMB) {
  50             options.inMutable = false;
  51         }
  52
  53         // make a false load of the bitmap to get its dimensions
  54         options.inJustDecodeBounds = true;
  55
  56         BitmapFactory.decodeFile(srcPath, options);
  57
  58         // calculate factor to subsample the bitmap
  59         options.inSampleSize = calculateSampleFactor(options, reqWidth, reqHeight);
  60
  61         // decode bitmap with inSampleSize set
  62         options.inJustDecodeBounds = false;
  63         return BitmapFactory.decodeFile(srcPath, options);
  64
  65     }
  66
  67
  68     /**
  69      * Calculates a proper value for options.inSampleSize in order to decode a Bitmap minimizing
  70      * the memory overload and covering a target surface of reqWidth x reqHeight if the original
  71      * image is big enough.
  72      *
  73      * @param options       Bitmap decoding options; options.outHeight and options.inHeight should
  74      *                      be set.
  75      * @param reqWidth      Width of the surface where the Bitmap will be drawn on, in pixels.
  76      * @param reqHeight     Height of the surface where the Bitmap will be drawn on, in pixels.
  77      * @return              The largest inSampleSize value that is a power of 2 and keeps both
  78      *                      height and width larger than reqWidth and reqHeight.
  79      */
  80     private static int calculateSampleFactor(Options options, int reqWidth, int reqHeight) {
  81
  82         final int height = options.outHeight;
  83         final int width = options.outWidth;
  84         int inSampleSize = 1;
  85
  86         if (height > reqHeight || width > reqWidth) {
  87             final int halfHeight = height / 2;
  88             final int halfWidth = width / 2;
  89
  90             while ((halfHeight / inSampleSize) > reqHeight
  91                     && (halfWidth / inSampleSize) > reqWidth) {
  92                 inSampleSize *= 2;
  93             }
  94         }
  95
  96         return inSampleSize;
  97     }
  98
  99 }