ppmファイルで使うグラデーション作るやつ

MakePicture.java

public class MakePicture {
    public static void main(String[] args){
        final int WIDTH = 255;
        final int HEIGHT = 255;
        RGB rgb = new RGB();
        System.out.println("P3 255 "+WIDTH+" "+HEIGHT);
        printRedBlueGradation(rgb,WIDTH,HEIGHT);
    }

    private static void printRedBlueGradation(RGB rgb, int width, int height){
        StringBuilder sb;
        for (int i=1;i<height;i++) {
            sb = new StringBuilder();
            for (int j = 1; j <= width; j++) {
                sb.append(rgb);
                sb.append(" ");
                rgb.addBlue(1);
            }
            System.out.println(sb);
            rgb.setBlue(0);
            rgb.addRed(1);
        }
    }

}

class RGB{
    private int red = 0;
    private int green = 0;
    private int blue = 0;
    private boolean doAutoCast = true;
    private static final int MAXRGB = 255;

    public RGB(int red, int green, int blue) {
        this.red = red;
        this.green = green;
        this.blue = blue;
    }
    public RGB() {
        this.red = 0;
        this.green = 0;
        this.blue = 0;
    }

    public void setAutoCast(boolean b) {this.doAutoCast = b;}

    public int getRed()             { return red; }
    public int getGreen()           { return green; }
    public int getBlue()            { return blue; }

    public void setRed(int red)     { this.red = this.cast(red); }
    public void setGreen(int green) { this.green = this.cast(green); }
    public void setBlue(int blue)   { this.blue = this.cast(blue); }

    public void addRed(int red)     { this.red = this.cast(this.red + red); }
    public void addGreen(int green) { this.green = this.cast(this.green + green); }
    public void addBlue(int blue)   { this.blue = this.cast(this.blue + blue); }

    private int cast(int i){
        if(this.doAutoCast) {
            while (i < 0 || MAXRGB < i) {
                if (i < 0) {
                    i += MAXRGB+1; //0〜255で合計256なので1を足す
                } else {
                    i -= MAXRGB+1; //同上
                }
            }
            return i;
        }else{
            throw new IllegalArgumentException();
        }
    }

    @Override
    public String toString() { return this.red+" "+this.green+" "+this.blue; }
}