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

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

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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 ; }

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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 ;     } }