FeThumbUtils.java 文件源码

private static int computeInitialSampleSize(BitmapFactory.Options options,
                                            int minSideLength, int maxNumOfPixels) {
    double w = options.outWidth;
    double h = options.outHeight;
    int lowerBound = (maxNumOfPixels == UNCONSTRAINED) ? 1 : (int) Math
            .ceil(Math.sqrt(w * h / maxNumOfPixels));
    int upperBound = (minSideLength == UNCONSTRAINED) ? 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 == UNCONSTRAINED)
            && (minSideLength == UNCONSTRAINED)) {
        return 1;
    } else if (minSideLength == UNCONSTRAINED) {
        return lowerBound;
    } else {
        return upperBound;
    }
}