Android : Converting color image to grayscale

Question

I am trying to convert color image into grayscale using the average of red, green, blue. But it comes out with errors.

Here is my code

imgWidth = myBitmap.getWidth();
imgHeight = myBitmap.getHeight();
                    
for(int i =0;i<imgWidth;i++) {
    for(int j=0;j<imgHeight;j++) {
     int s = myBitmap.getPixel(i, j)/3;
     myBitmap.setPixel(i, j, s);
    }
}
                    
ImageView img = (ImageView)findViewById(R.id.image1);
img.setImageBitmap(myBitmap);

But when I run my application on Emulator, it's force close. Any idea?

I have solved my problem use the following code:

for(int x = 0; x < width; ++x) {
            for(int y = 0; y < height; ++y) {
                // get one pixel color
                pixel = src.getPixel(x, y);
                // retrieve color of all channels
                A = Color.alpha(pixel);
                R = Color.red(pixel);
                G = Color.green(pixel);
                B = Color.blue(pixel);
                // take conversion up to one single value
                R = G = B = (int)(0.299 * R + 0.587 * G + 0.114 * B);
                // set new pixel color to output bitmap
                bmOut.setPixel(x, y, Color.argb(A, R, G, B));
            }
        }

Answer 1

You can do this too :

    ColorMatrix matrix = new ColorMatrix();
    matrix.setSaturation(0); 
    imageview.setColorFilter(new ColorMatrixColorFilter(matrix));