demo app showing the RGB representable colors of LAB

LAB gammut in RGB demo

	public static void main(String[] args) throws IOException {
		
		Img[] gammut = new Img[256];
		Consumer<Pixel> lab2rgb = (px)->{px.setValue(transformLAB2RGB(px.getValue()));};
		
		for(int l = 0; l < 256; l++){
			int L = l;
			Img img = new Img(256, 256);
			img.forEach(px->{px.setRGB(L, px.getX(), px.getY());});
			img.forEach(lab2rgb);
			gammut[l] = img;
		}
		
		int[] current = {0};
		ImageFrame frame = new ImageFrame();
		frame.setTitle("L="+current[0]);
		ImagePanel panel = frame.getPanel();
		panel.setImg(gammut[current[0]]);
		panel.addMouseWheelListener(e->{
			int plus = e.getWheelRotation();
			current[0] = (current[0] + 256 + plus) % 256;
			panel.setImg(gammut[current[0]]);
			frame.setTitle("L="+current[0]);
		});
		panel.getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, false), "UP");
		panel.getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, false), "DOWN");
		panel.getActionMap().put("UP", new AbstractAction() {
			@Override
			public void actionPerformed(ActionEvent e) {
				current[0] = (current[0] + 256 + 1) % 256;
				panel.setImg(gammut[current[0]]);
				frame.setTitle("L="+current[0]);
			}
		});
		panel.getActionMap().put("DOWN", new AbstractAction() {
			@Override
			public void actionPerformed(ActionEvent e) {
				current[0] = (current[0] + 256 -1) % 256;
				panel.setImg(gammut[current[0]]);
				frame.setTitle("L="+current[0]);
			}
		});
		frame.setVisible(true);
	}
	
	static int transformLAB2RGB(int val){
		float L = (Pixel.r_normalized(val)  )*100;
		float A = ((Pixel.g(val)-127)/254.0f)*200;
		float B = ((Pixel.b(val)-127)/254.0f)*200;
		
		// LAB to XYZ
		float temp = (L+16)/116;
		float x =  LAB.Xn*LAB.funcInv(temp + (A/500));
		float y =  LAB.Yn*LAB.funcInv(temp);
		float z =  LAB.Zn*LAB.funcInv(temp - (B/200));
		
		int r = Math.round(( 3.2404542f*x -1.5371385f*y -0.4985314f*z)*0xff );
		int g = Math.round((-0.9692660f*x +1.8760108f*y +0.0415560f*z)*0xff );
		int b = Math.round(( 0.0556434f*x -0.2040259f*y +1.0572252f*z)*0xff );
		int a = 255;
		if(isOut(r)||isOut(g)||isOut(b)){
			a = 0;
		}
		return Pixel.argb_bounded(a, r, g, b);
				
	}
	
	static boolean isOut(int val){
		return (val&0xff) != val;
	}
	
	private static final class LAB {
		static final float Xn = 0.95047f;
		static final float Yn = 1.00000f;
		static final float Zn = 1.08883f;
		static final float lab6_29 = 6.0f/29.0f;
		static final float lab6_29_3 = lab6_29*lab6_29*lab6_29;
		static final float lab1_3_29_6_2 = (1.0f/3.0f) * (29.0f/6.0f) * (29.0f/6.0f);

		static float func(float q){
			return q > lab6_29_3 ? (float)Math.cbrt(q):lab1_3_29_6_2*q + (4.0f/29.0f);
//			return (float)Math.cbrt(q);
		}

		static float funcInv(float q){
			return q > lab6_29 ? q*q*q : 3*lab6_29*lab6_29*(q-(4.0f/29.0f));
//			return q*q*q;
		}
	}