rgb image convert binary image in java bufferedImage

Question

I have a rgb image and i want to convert binary image 0-255.

I calculate threshold in rgb image and pixel which in gray level image bigger than threshold, i set red = 255 green=255 and blue=255 and lower than threshold i set red = 0 green=0 and blue=0

private static int colorToRGB(int alpha, int red, int green, int blue) {
    int newPixel = 0;
    newPixel += alpha;
    newPixel = newPixel << 8;
    newPixel += red; newPixel = newPixel << 8;
    newPixel += green; newPixel = newPixel << 8;
    newPixel += blue;
    System.out.println("asd"  + newPixel);
    return newPixel;
}

newPixel's value -16777216 if pixel is white newPixel's value -1 if pixel is black

alpha value is constant 255 Where am i wrong because i want to pixel's value 0 and 255.

BufferedImage type is TYPE_INT_ARGB

Thank you for helping

Renard Renard · Accepted Answer · 2012-04-14T21:02:34

Honestly your question doesn't make much sense to me. So i answer your question making some assumptions:

you have a global threshold [0-255]
the threshold should be applied to a grayscale value so you need to convert the rgb pixels to grayscale values
the procedure should be as fast as possible
you want to do it in java

This function takes the rgb color and the threshold and returns either black or white.

public static int treshold(final int sourceColor, final int treshold) {
    // green channel is a good approximation of rgb intensity
    int green = (sourceColor >> 8) & 0xFF;
    if (green < treshold) {
        return 0xFF000000;
    } else {
        return 0xFFFFFFFF;
    }
}

rgb image convert binary image in java bufferedImage

3 Answers