code in calculateInSampleSize method about androidstudycode

[D-clock]

@hotstu

let me tell you ,

            long totalPixels = width * height / inSampleSize;
            final long totalReqPixelsCap = reqWidth * reqHeight * 2;
            while (totalPixels > totalReqPixelsCap) {
                inSampleSize *= 2;
                totalPixels /= 2;
            }

This code is to deal with a large picture of the length or width of the case.It is OR,not AND.So I chose the code —— long totalPixels = width * height / inSampleSize; Do you understand？

[hotstu]

i wrote a compare

    public static int calculateInSampleSize(int rawW, int rawH, int reqWidth, int reqHeight) {
        final int height = rawH;
        final int width = rawW;
        int inSampleSize = 1;
        if (height > reqHeight || width > reqWidth) {
            final int halfHeight = height / 2;
            final int halfWidth = width / 2;
            while ((halfHeight / inSampleSize) > reqHeight && (halfWidth / inSampleSize) > reqWidth) {
                inSampleSize *= 2;
            }
            long totalPixels = width * height / inSampleSize;
            final long totalReqPixelsCap = reqWidth * reqHeight * 2;
            while (totalPixels > totalReqPixelsCap) {
                inSampleSize *= 2;
                totalPixels /= 2;
            }
        }
        return inSampleSize;
    }
    public static int calculateInSampleSize2(int rawW, int rawH, int reqWidth, int reqHeight) {
        final int height = rawH;
        final int width = rawW;
        int inSampleSize = 1;
        while ((height / inSampleSize) > reqHeight || (width / inSampleSize) > reqWidth) {
            inSampleSize *= 2;
        }
        return inSampleSize;
    }

    public static int calculateInSampleSize3(int rawW, int rawH, int reqWidth, int reqHeight) {
        final int height = rawH;
        final int width = rawW;
        int inSampleSize = 1;
        long totalPixels = width * height / (inSampleSize* inSampleSize);
        final long totalReqPixelsCap = reqWidth * reqHeight;
        while (totalPixels > totalReqPixelsCap) {
            inSampleSize *= 2;
            totalPixels = width * height / (inSampleSize* inSampleSize);
        }
        return inSampleSize;
    }
    public static void main(String[] args) {
        System.err.println(calculateInSampleSize(20, 1000, 100, 100));
        System.err.println(calculateInSampleSize2(20, 1000, 100, 100));
        System.err.println(calculateInSampleSize3(20, 1000, 100, 100));
        System.err.println("-----------");
        System.err.println(calculateInSampleSize(1000, 1000, 100, 100));
        System.err.println(calculateInSampleSize2(1000, 1000, 100, 100));
        System.err.println(calculateInSampleSize3(1000, 1000, 100, 100));
        System.err.println("-----------");
        System.err.println(calculateInSampleSize(1000, 10, 100, 100));
        System.err.println(calculateInSampleSize2(1000, 10, 100, 100));
        System.err.println(calculateInSampleSize3(1000, 10, 100, 100));
        System.err.println("-----------");
        System.err.println(calculateInSampleSize(10000, 10000, 100, 100));
        System.err.println(calculateInSampleSize2(10000, 10000, 100, 100));
        System.err.println(calculateInSampleSize3(10000, 10000, 100, 100));
    }

and the output:

1
16
2
-----------
64
16
16
-----------
1
16
1
-----------
8192
128
128

[D-clock]

@hotstu hi，friend！You need to use real photo data！