convsion from RGB to CIE XYZ and further to CIE Lab and all the way back

RGB2XYZ2LAB and back

public static void main(String[] args) throws MalformedURLException, IOException {
//		String imgUrl = "http://sipi.usc.edu/database/preview/misc/4.1.07.png";
		String imgUrl = "http://sipi.usc.edu/database/preview/misc/boat.512.png";
		Img img = Img.createRemoteImg(ImageLoader.loadImage(new URL(imgUrl).openStream(),BufferedImage.TYPE_INT_ARGB));
		
		System.out.println("start");
		
		// to CIE XYZ colorspace (bound to [0..255] missing the factor 1/0.17697)
		img.forEachParallel(px->{
			px.setARGB(	px.a(), 
					px.getGrey(   49,    31,    20),
					px.getGrey(17697, 81240,  1063), 
					px.getGrey(    0,     1,    99));
		});
		
		// CIE XYZ to CIE LAB also bound to [0..255] with 128 being 0 chromaticity
		final float labX = 255f;
		final float labY = 255f;
		final float labZ = 255f;
		img.forEachParallel(px->{
			float X = px.r();
			float Y = px.g();
			float Z = px.b();
			
			float temp = labFunc(Y/labY);
			int L = (int) (255*temp);
			int a = (int) (127*(labFunc(X/labX)-temp)+128);
			int b = (int) (127*(temp-labFunc(Z/labZ))+128);
			px.setARGB(px.a(), L, a, b);
		});
		
		// do something with Lab
		img.forEachParallel(px->{
				float L = px.r();
				float a = px.g()-128;
				float b = px.b()-128;
				
				float len = (float)Math.sqrt(a*a+b*b);
				float angle =(float)Math.atan2(a, b);
				
				len = 5;
				angle = (float) ((L+280)*(Math.PI/180));
				
				a = (float) (Math.sin(angle)*len);
				b = (float) (Math.cos(angle)*len);
				
				px.setValue(Pixel.argb_bounded(px.a(), (int)L, (int)a+128, (int)b+128));
		});
				
		// backtransform to XYZ
		img.forEachParallel(px->{
			float temp = px.r()/255.0f; // =L/255
			int X = (int) (labX*labFuncInv(temp + (px.g()-128)/127.0f));
			int Y = (int) (labY*labFuncInv(temp));
			int Z = (int) (labZ*labFuncInv(temp - (px.b()-128)/127.0f));
			px.setValue(Pixel.argb_bounded(px.a(), (int)X, (int)Y, (int)Z));
		});
		
		// CIE XYZ to RGB (for XYZ bound to [0..255] missing factor 1/0.17697)
		img.forEachParallel(px->{
			int r = px.getGrey(23646,  -8966,   -4680);
			int g = px.getGrey(-5151,  14264,     887);
			int b = px.getGrey(   52,   -144,   10092);
			px.setValue(Pixel.argb_bounded(px.a(),r, g, b));
		});

		System.out.println("done");
		
		ImageSaver.saveImage(img.getRemoteBufferedImage(), "export.png");
	}
	
	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 labFunc(float q){
		return q > lab6_29_3 ? (float)Math.cbrt(q):lab1_3_29_6_2*q + (4.0f/29.0f);
	}
	
	static float labFuncInv(float q){
		return q > lab6_29 ? q*q*q : 3*lab6_29*lab6_29*(q-(4.0f/29.0f));
	}