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; } }