Take Monochrome Picture (black And White) With Android

I would like to take a picture in true black and white in my app. I searched for solutions (in this site too), but I always found solution to put a photo in gray scale (for example

Solution 1:

If you like the image to be 1bit black/white you can use a simple (& slow) threshold algorithm

publicstatic Bitmap createBlackAndWhite(Bitmap src) {
    intwidth= src.getWidth();
    intheight= src.getHeight();
    // create output bitmapBitmapbmOut= Bitmap.createBitmap(width, height, src.getConfig());
    // color informationint A, R, G, B;
    int pixel;

    // scan through all pixelsfor (intx=0; x < width; ++x) {
        for (inty=0; y < height; ++y) {
            // get pixel color
            pixel = src.getPixel(x, y);
            A = Color.alpha(pixel);
            R = Color.red(pixel);
            G = Color.green(pixel);
            B = Color.blue(pixel);
            intgray= (int) (0.2989 * R + 0.5870 * G + 0.1140 * B);

            // use 128 as threshold, above -> white, below -> blackif (gray > 128) 
                gray = 255;
            elsegray=0;
            // set new pixel color to output bitmap
            bmOut.setPixel(x, y, Color.argb(A, gray, gray, gray));
        }
    }
    return bmOut;
}

But depending on what that will not look good, for better results you need a dithering algorithm, see Algorithm overview - this one is the threshold method.

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For 256 levels of gray conversion:

according to http://www.mathworks.de/help/toolbox/images/ref/rgb2gray.html you calculate the gray value of each pixel as gray = 0.2989 * R + 0.5870 * G + 0.1140 * B which would translate to

publicstatic Bitmap createGrayscale(Bitmap src) {
    intwidth= src.getWidth();
    intheight= src.getHeight();
    // create output bitmapBitmapbmOut= Bitmap.createBitmap(width, height, src.getConfig());
    // color informationint A, R, G, B;
    int pixel;

    // scan through all pixelsfor (intx=0; x < width; ++x) {
        for (inty=0; y < height; ++y) {
            // get pixel color
            pixel = src.getPixel(x, y);
            A = Color.alpha(pixel);
            R = Color.red(pixel);
            G = Color.green(pixel);
            B = Color.blue(pixel);
            intgray= (int) (0.2989 * R + 0.5870 * G + 0.1140 * B);
            // set new pixel color to output bitmap
            bmOut.setPixel(x, y, Color.argb(A, gray, gray, gray));
        }
    }
    return bmOut;
}

But that is pretty slow since you have to do that for millions of pixels separately.

https://stackoverflow.com/a/9377943/995891 has a much nicer way of achieving the same.

// code from that answer put into method from abovepublicstatic Bitmap createGrayscale(Bitmap src) {
    intwidth= src.getWidth();
    intheight= src.getHeight();
    BitmapbmOut= Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    Canvascanvas=newCanvas(bmOut);
    ColorMatrixma=newColorMatrix();
    ma.setSaturation(0);
    Paintpaint=newPaint();
    paint.setColorFilter(newColorMatrixColorFilter(ma));
    canvas.drawBitmap(src, 0, 0, paint);
    return bmOut;
}

Solution 2:

G = Color.red(pixel);

G = Color.green(pixel);

B = Color.red(pixel);

B = Color.blue(pixel);

See if this changes (in bold) helps.