Java hsb degrees or 255

Question

I was wondering if when you call color.HSBtoRGB if the hue value would be entered as a range of 0-255, 0-1, 0-360? I am inquiring because I am trying to convert an edge angle to a color but it is only giving me blue or purple? can anyone explain what I am doing?

public void sobelGrey(){
    this.greyScale();
    double edgex;
    double edgey;
    Picture pi = new Picture(this.getWidth(), this.getHeight());
    Picture tou = new Picture(this.getWidth(), this.getHeight());
    Pixel[][] Y = pi.getPixels2D();
    Pixel[][] X = tou.getPixels2D();
    Pixel[][] h = this.getPixels2D();
    for (int y = 1; y< X.length-1; y++){
        for(int x= 1; x<X[1].length-1; x++){
            edgex =
                    h[y-1][x-1].getRed() * -1 +
                            h[y][x-1].getRed()  * -2+
                            h[y+1][x-1].getRed()  * -1+
                            h[y-1][x+1].getRed() * 1 +
                            h[y][x+1].getRed()  * 2+
                            h[y+1][x+1].getRed()  * 1;
            Y[y][x].setRed((int)Math.abs(edgex/2));
            Y[y][x].setGreen((int)Math.abs(edgex/2));
            Y[y][x].setBlue((int)Math.abs(edgex/2));
        }
    }

    for (int y = 1; y< X.length-1; y++){
        for(int x= 1; x<X[1].length-1; x++){
            edgex =
                    h[y-1][x-1].getRed() * -1 +
                            h[y-1][x].getRed()  * -2+
                            h[y-1][x+1].getRed()  * -1+
                            h[y+1][x-1].getRed() * 1 +
                            h[y+1][x].getRed()  * 2+
                            h[y+1][x+1].getRed()  * 1;
            X[y][x].setRed((int)Math.abs(edgex/2));
            X[y][x].setGreen((int)Math.abs(edgex/2));
            X[y][x].setBlue((int)Math.abs(edgex/2));
        }
    }

    for (int y = 1; y< X.length-1; y++){
        for(int x= 1; x<X[1].length-1; x++){
            int x1 = (int) Math.sqrt(Math.pow(X[y][x].getRed(), 2) + Math.pow(X[y][x].getGreen(), 2) + Math.pow(X[y][x].getBlue(), 2));
            int y1 = (int) Math.sqrt(Math.pow(Y[y][x].getRed(), 2) + Math.pow(Y[y][x].getGreen(), 2) + Math.pow(Y[y][x].getBlue(), 2));
            int hr = (int) (200/(2*Math.PI)*(Math.tanh(y1/ (x1+.000000000000001))));

            int rgb = Color.HSBtoRGB(hr/255, hr, (int) Math.sqrt(Math.pow(x1, 2) + Math.pow(y1, 2)));
            Color fixed = new Color(rgb&0xFF*7/10, (rgb>>8)&0xFF*80/255/10, (rgb>>16)&0xFF*4/10);
            if( !(Math.sqrt(Math.pow(x1, 2) + Math.pow(y1, 2))< 40))
            h[y][x].setColor(fixed);
            else
                h[y][x].setColor(Color.black);
        }
    }
    pi.explore();
    tou.explore();
    explore();
}

i am using a computer science AP image processing from Eimacs, and using the swan

Maybe if you show us your code we could help tell you what's wrong with it. — takendarkk, Apr 17 '18 at 18:36

score 0 · Accepted Answer · answered Apr 17 '18 at 19:56

0

You declared hr (and the other variables) to be an int. Then in Color.HSBtoRGB(hr/255, ... you divide an int by an int. For all values of hr below 255, the result will be 0.

Probably it is sufficient to divide by 255.0 to force a floating point division.

answered Apr 17 '18 at 19:56

Rainer Schwarze

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so the hue is in a range of 0-1? – mark anthony Apr 17 '18 at 20:05
All arguments are 0..1:, hue 0-1 = 0-360deg (quick google revealed this: https://docs.oracle.com/javase/7/docs/api/java/awt/Color.html ) – Rainer Schwarze Apr 17 '18 at 21:10
OK, thanks. do you happen to know how to thin out the edges so they are one pixel thick and not 4 thick? – mark anthony Apr 19 '18 at 18:36
Sorry - no. It has been some time since I worked with such things. – Rainer Schwarze Apr 20 '18 at 13:36

Java hsb degrees or 255

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