Coursera - Computer Science: Programming With A Purpose

Week 9: Creating Data Types - Color Data Type

Jul 1, 2020

Write a data type ColorHSB.java that represents a color in hue–saturation–brightness (HSB) format, along with a sample client. The HSB color format is widely used in color pickers.

HSB = (240°, 100%, 100%)

A color in HSB format is composed of three components:

The hue is an integer between 0 and 359. It represents a pure color on the color wheel, with 0° for red, 120° for green, and 240° for blue.
The saturation is an integer between 0 and 100. It represents the purity of the hue.
The brightness is an integer between 0 and 100. It represents the percentage of white that is mixed with the hue.

Implement the following public API:

public class ColorHSB {

    // Creates a color with hue h, saturation s, and brightness b.
    public ColorHSB(int h, int s, int b)

    // Returns a string representation of this color, using the format (h, s, b).
    public String toString()

    // Is this color a shade of gray?
    public boolean isGrayscale()

    // Returns the squared distance between the two colors.
    public int distanceSquaredTo(ColorHSB that)

    // Sample client (see below).
    public static void main(String[] args)
}

Here is some more information about the required behavior:

Corner cases. Throw an IllegalArgumentException in the constructor if any component is outside its prescribed range (0 to 359 for the hue, 0 to 100 for the saturation and brightness); throw an IllegalArgumentException in distanceSquaredTo() if its argument is null.
String representation. Return a string composed of the integers for hue, saturation, and brightness (in that order), separated by commas, and enclosed in parentheses. An example is (26, 85, 96).
Grayscale. A color in HSB format is a shade of gray if either its saturation or brightness component is 0% (or both).
Distance. The squared distance between two colors (h1,s1,b1) and (h2,s2,b2) is defined to be

min { (h₁ − h₂) ² , (360 − |h₁ − h₂|) ² } + (s₁ − s₂) ² + (b₁ − b₂) ²

For example, the squared distance between (350, 100, 45) and (0, 100, 50) is 10 ² + 0 ² + 52 = 125.
Sample client. The main() method should take three integer command-line arguments h, s, and b; read a list of pre-defined colors from standard input; and print to standard output the pre-defined color that is closest to (h,s,b).
- Input specification. The input from standard input consists of a sequence of one or more lines. Each line contains a string (the name of a pre-defined color) and three integers (its hue, saturation, and brightness components), separated by whitespace. The data files web.txt and web.txt are in the specified format.
- Output specification. The output to standard output consists of one line: the name of the nearest pre-defined color and the string representation of that color, separated by whitespace.

~/Desktop/oop2> java ColorHSB 25 84 97 < web.txt
Red (0, 100, 100)

~/Desktop/oop2> java ColorHSB 350 100 45 < web.txt
Maroon (0, 100, 50)

~/Desktop/oop2> java ColorHSB 25 84 97 < wiki.txt
Princeton_Orange (26, 85, 96)

Note: the above description is copied from Coursera and converted to markdown for convenience

Solution:

public class ColorHSB {

    private static final int MAX_HUE = 359;
    private static final int MAX_SATURATION = 100;
    private static final int MAX_BRIGHTNESS = 100;

    private final int hue;          // 0...359, 0 = red, 120 = green, 24 = blue
    private final int saturation;   // 0...100
    private final int brightness;   // 0...100

    // Creates a color with hue h, saturation s, and brightness b.
    public ColorHSB(int h, int s, int b) {
        if ((h < 0) || (h > MAX_HUE)) {
            throw new IllegalArgumentException();
        }
        if ((s < 0) || (s > MAX_SATURATION)) {
            throw new IllegalArgumentException();
        }
        if ((b < 0) || (b > MAX_BRIGHTNESS)) {
            throw new IllegalArgumentException();
        }
        hue = h;
        saturation = s;
        brightness = b;
    }

    // Returns a string representation of this color, using the format (h, s, b).
    public String toString() {
        return "(" + hue + ", " + saturation + ", " + brightness + ")";
    }

    // Is this color a shade of gray?
    public boolean isGrayscale() {
        return (saturation == 0) || (brightness == 0);
    }

    // Returns the squared distance between the two colors.
    public int distanceSquaredTo(ColorHSB that) {
        if (that == null) {
            throw new IllegalArgumentException();
        }
        return (int) (Math.min(Math.pow(hue - that.hue, 2), Math.pow(360 - Math.abs(hue - that.hue), 2))
                + Math.pow(saturation - that.saturation, 2)
                + Math.pow(brightness - that.brightness, 2));
    }

    // Sample client (see below).
    public static void main(String[] args) {
        final int h = Integer.parseInt(args[0]);
        final int s = Integer.parseInt(args[1]);
        final int b = Integer.parseInt(args[2]);
        final ColorHSB colorHSB1 = new ColorHSB(h, s, b);
        int closestDistance = Integer.MAX_VALUE;
        String closestColorName = null;
        ColorHSB closestColorHSB = null;
        while (StdIn.hasNextLine() && !StdIn.isEmpty()) {
            final String colorName = StdIn.readString();
            final int h2 = StdIn.readInt();
            final int s2 = StdIn.readInt();
            final int b2 = StdIn.readInt();
            final ColorHSB colorHSB2 = new ColorHSB(h2, s2, b2);
            final int distance = colorHSB1.distanceSquaredTo(colorHSB2);
            if (distance < closestDistance) {
                closestDistance = distance;
                closestColorName = colorName;
                closestColorHSB = colorHSB2;
            }
        }
        StdOut.println(closestColorName + " " + closestColorHSB);
    }
}

Link To: Java Source Code