How to change hue, saturation, and luminance of an image in android

Question

I want to change the hue for specific color on image. I have searched many times but found nothing. Currently I'm using this piece of code i get from SO for changing image hue.

public static class ColorFilterGenerator {
    static ColorFilter adjustHue(float value)
    {
        ColorMatrix cm = new ColorMatrix();

        adjustHues(cm, value);

        return new ColorMatrixColorFilter(cm);
    }

    static void adjustHues(ColorMatrix cm, float value) {
        value = cleanValue(value) / 180f * (float) Math.PI;
        if (value != 0) {
            float cosVal = (float) Math.cos(value);
            float sinVal = (float) Math.sin(value);
            float lumR = 0.213f;
            float lumG = 0.715f;
            float lumB = 0.072f;
            float[] mat = new float[]
                    {
                            lumR + cosVal * (1 - lumR) + sinVal * (-lumR), lumG + cosVal * (-lumG) + sinVal * (-lumG), lumB + cosVal * (-lumB) + sinVal * (1 - lumB), 0, 0,
                            lumR + cosVal * (-lumR) + sinVal * (0.143f), lumG + cosVal * (1 - lumG) + sinVal * (0.140f), lumB + cosVal * (-lumB) + sinVal * (-0.283f), 0, 0,
                            lumR + cosVal * (-lumR) + sinVal * (-(1 - lumR)), lumG + cosVal * (-lumG) + sinVal * (lumG), lumB + cosVal * (1 - lumB) + sinVal * (lumB), 0, 0,
                            0f, 0f, 0f, 1f, 0f,
                            0f, 0f, 0f, 0f, 1f};
            cm.postConcat(new ColorMatrix(mat));
        }
    }

    static float cleanValue(float p_val)
    {
        return Math.min((float) 180.0, Math.max(-(float) 180.0, p_val));
    }
}

But this code changes the whole image hue while dragging the seekbar. Can someone please tell me how can i achieve this for a specific color (like only for red) ? Thank you.

Answer 1

You could use OpenCV for Android . Then you can read the image in and convert to HSV and then change the hue directly.

Mat image_bgr = Imgcodecs.imread("image_path");
Mat image_hsv = image_bgr.clone();
Imgproc.cvtColor(image_bgr, image_hsv, Imgproc.COLOR_BGR2HSV);

double hue = ...
for (int row = 0; row < image_hsv.rows(); row++) {
    for (int col = 0; col < image_hsv.cols(); col++) {
        double[] pixel = image_hsv.get(row, col);
        pixel[0] += hue;
        image_hsv.put(row, col, pixel);
    }
}