ImageSize.java

package com.third.imgload;

import android.graphics.BitmapFactory;

public class ImageSize {
	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;
	    }
	}
}