public static int computeSampleSize(BitmapFactory.Options options, int minSideLength, int maxNumOfPixels) {

int initialSize = computeInitialSampleS

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ize(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。

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) {

}

综合上述，完整代码是：

[java]

view plain

copy

1. public static Bitmap createImageThumbnail(String filePath){

2. Bitmap bitmap = null;

3. BitmapFactory.Options opts = new BitmapFactory.Options();

4. opts.inJustDecodeBounds = true;

5. BitmapFactory.decodeFile(filePath, opts);

6. opts.inSampleSize = computeSampleSize(opts, -1, 128*128);

7. opts.inJustDecodeBounds = false;

8. try {

9. bitmap = BitmapFactory.decodeFile(filePath, opts);

10. }catch (Exception e) {

11. // TODO: handle exception

12. }

13. return bitmap;

14. }

15. public static int computeSampleSize(BitmapFactory.Options options, int minSideLength, int maxNumOfPixels) {

16. int initialSize = computeInitialSampleSize(options, minSideLength, maxNumOfPixels);

17. int roundedSize;

18. if (initialSize <= 8) {

19. roundedSize = 1;

20. while (roundedSize < initialSize) {

21. roundedSize <<= 1;

22. }

23. } else {

24. roundedSize = (initialSize + 7) / 8 * 8;

25. }

26. return roundedSize;

27. }

28. private static int computeInitialSampleSize(BitmapFactory.Options options,int minSideLength, int maxNumOfPixels) {

29. double w = options.outWidth;

30. double h = options.outHeight;

31. int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math.sqrt(w * h / maxNumOfPixels));

32. int upperBound = (minSideLength == -1) ? 128 :(int) Math.min(Math.floor(w / minSideLength), Math.floor(h / minSideLength));

33. if (upperBound < lowerBound) {

34. // return the larger one when there is no overlapping zone.