Binarize Image in Android

Question

I am developing android app that uses tesseract OCR to scan a text from image,
I heard that binarizing image before performing OCR on it will give better result,
So

Answer 1

I have to do a similar task as part of a project for an asignment. I found in my workspace this piece of code, I think this is what you need:

Bitmap img = BitmapFactory.decodeResource(this.getResources(), drawable.testimage);
Paint paint = new Paint();

ColorMatrix cm = new ColorMatrix();
float a = 77f;
float b = 151f;
float c = 28f;
float t = 120 * -256f;
cm.set(new float[] { a, b, c, 0, t, a, b, c, 0, t, a, b, c, 0, t, 0, 0, 0, 1, 0 });
paint.setColorFilter(new ColorMatrixColorFilter(cm));
canvas.drawBitmap(img, 0, 0, paint);

Here I used ColorMatrix to generate a black and white image from a color one. Also I found this piece of code that I used to convert a color image to a gray scale image:

Bitmap result = Bitmap.createBitmap(destWidth, destHeight,Bitmap.Config.RGB_565);
RectF destRect = new RectF(0, 0, destWidth, destHeight);
Canvas canvas = new Canvas(result);
Paint paint = new Paint();
ColorMatrix colorMatrix = new ColorMatrix();
colorMatrix.setSaturation(0);
ColorFilter filter = new ColorMatrixColorFilter(colorMatrix);
paint.setColorFilter(filter);
canvas.drawBitmap(bitmap, sourceRect, destRect, paint); 

Hope this help you.