当图片过大，或图片数量较多时使用BitmapFactory解码图片会出java.lang.OutOfMemoryError: bitmap size exceeds VM budget，要想正常使用则需分配更少的内存，具体的解决办法是修改采样值BitmapFactory.Options.inSampleSize，例如：java
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BitmapFactory.Options opts = new BitmapFactory.Options(); opts.inSampleSize = 4; Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts); |
如何设置恰当的inSampleSize算法
设置恰当的inSampleSize是解决该问题的关键之一。BitmapFactory.Options提供了另外一个成员inJustDecodeBounds。app
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BitmapFactory.Options opts = new BitmapFactory.Options(); opts.inJustDecodeBounds = true; Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts); |
设置inJustDecodeBounds为true后，decodeFile并不分配空间，但可计算出原始图片的长度和宽度，即opts.width和opts.height。有了这两个参数，再经过必定的算法，便可获得一个恰当的inSampleSize。ide
查看Android源码，Android提供了一种动态计算的方法。code
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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;
}} |
使用该算法，就可动态计算出图片的inSampleSize。图片
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BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;BitmapFactory.decodeFile(imageFile, opts);
opts.inSampleSize = computeSampleSize(opts, -1, 128*128);
opts.inJustDecodeBounds = false;
try {
Bitmap bmp = BitmapFactory.decodeFile(imageFile, opts);
imageView.setImageBitmap(bmp);
} catch (OutOfMemoryError err) {} |
此办法只是获取的图片的缩略图，可能会形成失真！内存