BitmapFactory.decodeByteArray() returns null on binarized Bitmap

Question

I have a byte array with series of 0 and -1 (255). It's a result of binarization using the Otsu algorithm. I used:

BitmapFactory.Options opt = new BitmapFactory.Options();
opt.inDither = true;
opt.inPreferredConfig = Bitmap.Config.RGB_565; // I have tried ARGB_8888 aswell

Bitmap out = BitmapFactory.decodeByteArray(data, 0, data.length, opt);

Unfortunately, it returns null. Just like the other questions regarding BitmapFactory.decodeByteArray() .

I have tested other methods like nested for loops, it works but it takes too long to process, especially for large images.

This is what I currently use to generate the binarized data :

ptr = 0;
while (ptr < srcData.length)
{
    monoData[ptr] = ((0xFF & srcData[ptr]) >= threshold) ? (byte) 255 : 0;
    ptr ++;
}

I hope you can lead me to a better way on solving this issue. Thanks!

Answer 1

565 is a representation that uses 2 bytes per pixel.

Moreover, decodeByteArray is a method that reads a compressed byte[] (see documentation).

Here is what I would do :

• use a int[] rather than a byte[].
• initialize like follows
• use Bitmap.html#createBitmap() method with the int[] resulting. The config used is not really important at this point.

monoData[ptr] = ((0xFF & srcData[ptr]) >= threshold) ? 0xffffffff : 0xff000000;

nota : one thing that could have helped you : decodeByteArray has no idea of the geometry of your image, hence can of course not decode it to what you are expected.