Android使用BitmapFactory.Options解决加载大图片内存溢出问题

Android使用BitmapFactory.Options解决加载大图片内存溢出问题

http://orgcent.com/android-outofmemoryerror-load-big-image/

由于Android对图片使用内存有限制，若是加载几兆的大图片便内存溢出。Bitmap会将图片的所有像素（即长x宽）加载到内存中，如果图片分辨率过大，会直接导致内存溢出（java.lang.OutOfMemoryError），只有在BitmapFactory加载图片时使用BitmapFactory.Options对相关参数进行配置来减少加载的像素。

1、设置缩放大小对图片作处理

public Bitmap getBitmapFromFile(File dst, int width, int height) {     if (null != dst && dst.exists()) {         BitmapFactory.Options opts = null;         if (width > 0 && height > 0) {             opts = new BitmapFactory.Options();             opts.inJustDecodeBounds = true;             BitmapFactory.decodeFile(dst.getPath(), opts);             // 计算图片缩放比例             final int minSideLength = Math.min(width, height);             opts.inSampleSize = computeSampleSize(opts, minSideLength,                     width * height);             opts.inJustDecodeBounds = false;             opts.inInputShareable = true;             opts.inPurgeable = true;         }         try {             return BitmapFactory.decodeFile(dst.getPath(), opts);         } catch (OutOfMemoryError e) {             e.printStackTrace();         }     }     return null; }

public static int computeSampleSize(BitmapFactory.Options options,         int minSideLength, int maxNumOfPixels) {     int initialSize = computeInitialSampleSize(options, minSideLength,             maxNumOfPixels);     int roundedSize;     if (initialSize <= 8) {         roundedSize = 1;         while (roundedSize < initialSize) {             roundedSize <<= 1;         }     } else {         roundedSize = (initialSize + 7) / 8 * 8;     }     return roundedSize; } private static int computeInitialSampleSize(BitmapFactory.Options options,         int minSideLength, int maxNumOfPixels) {     double w = options.outWidth;     double h = options.outHeight;     int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math             .sqrt(w * h / maxNumOfPixels));     int upperBound = (minSideLength == -1) ? 128 : (int) Math.min(Math             .floor(w / minSideLength), Math.floor(h / minSideLength));     if (upperBound < lowerBound) {         // return the larger one when there is no overlapping zone.         return lowerBound;     }     if ((maxNumOfPixels == -1) && (minSideLength == -1)) {         return 1;     } else if (minSideLength == -1) {         return lowerBound;     } else {         return upperBound;     } }