How adjust brightness of bitmap in gradient format in android?

Question

I have seen so many links and posts of to adjust birightness of bitmap in android, but i want to adjust brightness with gradient, like adjust brightness of only center of the bitmap. Anybody have any idea how to do this ?

Answer 1

You can generate a bitmap and draw a gradient:

How to draw a smooth/dithered gradient on a canvas in Android

Then use each pixel from gradient bitmap and get the brightness and pass it to the function that adjust brightness.

look here Formula to determine brightness of RGB color

public Bitmap SetBrightness(Bitmap src, Bitmap gradient) {
    // original image size
    int width = src.getWidth();
    int height = src.getHeight();
    // create output bitmap
    Bitmap bmOut = Bitmap.createBitmap(width, height, src.getConfig());
    // color information
    int A, R, G, B;
    int pixel;

    // scan through all pixels
    for (int x = 0; x < width; ++x) {
        for (int y = 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);

            int gradientPixel = gradient.getPixel(x, y);
            int value = getLuminance(gradientPixel);                

            // increase/decrease each channel
            R += value;
            if (R > 255) {
                R = 255;
            }
            else if (R < 0) {
                R = 0;
            }

            G += value;
            if (G > 255) {
                G = 255;
            }
            else if (G < 0) {
                G = 0;
            }

            B += value;
            if (B > 255) {
                B = 255;
            }
            else if (B < 0) {
                B = 0;
            }

            // apply new pixel color to output bitmap
            bmOut.setPixel(x, y, Color.argb(A, R, G, B));
        }
    }

    // return final image
    return bmOut;
}

public int getLuminance(int pixel) {
    int A, R, G, B;
    A = Color.alpha(pixel);
    R = Color.red(pixel);
    G = Color.green(pixel);
    B = Color.blue(pixel);

    return (0.2126 * R) + (0.7152 * G) + (0.0722 * B);
}