BitmapFactory.decodeFile(imageFile);
用BitmapFactory解碼一張圖片時。有時會遇到該錯誤。
這往往是因為圖片過大造成的。
要想正常使用，則須要分配更少的內存空間來存儲。
BitmapFactory.Options.inSampleSize
設置恰當的inSampleSize能夠使BitmapFactory分配更少的空間以消除該錯誤。inSampleSize的詳細含義請參考SDK文檔。
比如：
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inSampleSize = 4;
Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);
設置恰當的inSampleSize是解決該問題的關鍵之中的一個。BitmapFactory.Options提供了還有一個成員inJustDecodeBounds。
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);
設置inJustDecodeBounds為true后，decodeFile並不分配空間。但可計算出原始圖片的長度和寬度，即opts.width和opts.height。有了這兩個參數，再通過一定的算法，就可以得到一個恰當的inSampleSize。
public static Bitmap createImageThumbnail(String filePath){
Bitmap bitmap = null;
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
BitmapFactory.decodeFile(filePath, opts);
opts.inSampleSize = computeSampleSize(opts, -1, 128*128);
opts.inJustDecodeBounds = false;
try {
bitmap = BitmapFactory.decodeFile(filePath, opts);
}catch (Exception e) {
// TODO: handle exception
}
return bitmap;
}
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;
}
}
