Modifying colours on MSX1...?

Assuming that the problem is emulators working on the RGB model which is problematic for TV effects,
I coded the linemixer algo in RGB.
I checked on real machine, same thing, too makes a solid plane of new mixcolor, it is great!

The tool shows images like on TV, load an image and see.
The linemix() function is easily done to C.

to get it running type

javac linemix.java
java linemix

it will load the image "test.png".

the source

import java.io.*;
import java.util.*;

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.imageio.*;

import javax.swing.*;
import javax.swing.event.*;

public class linemix {
	BufferedImage loadimage(File f) {
		try { return ImageIO.read(f); } catch (Exception e) { System.err.println("IMAGEIO.read: " + e); } return null;
	}
	void saveimage(BufferedImage img, File f, String type) {
		try { ImageIO.write(img, type, f); } catch (Exception e) { System.err.println("IMAGEIO.write: " + e); }
	}
	
	public static void main(String args[]) { new linemix().main2(args); }
	
	class framelauncher implements Runnable {
		int w,h; frame f;
		public void run() {

			cimg ci = new cimg(w, h);
			
			JScrollPane scroll = new JScrollPane();
			scroll.setVerticalScrollBarPolicy(scroll.VERTICAL_SCROLLBAR_ALWAYS);
			scroll.setHorizontalScrollBarPolicy(scroll.HORIZONTAL_SCROLLBAR_ALWAYS);
			scroll.getViewport().add(ci);
			scroll.getViewport().setScrollMode(JViewport.SIMPLE_SCROLL_MODE);

			f = new frame(); f.framescr = ci; 
			f.addKeyListener(ci);
	
			f.add(scroll); //f.add(ci); 
			f.resize(800,600); //f.pack(); 
			f.show(); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		}
	}
	
	public class frame extends JFrame {
		public cimg framescr;
	}

	
	public class cimg extends JPanel implements KeyListener {
		
		public void	keyPressed(KeyEvent e) {
		}//        Invoked when a key has been pressed.
		public void	keyReleased(KeyEvent e) { /*showbitmap = false; repaint();*/ }//          Invoked when a key has been released.
		public void	keyTyped(KeyEvent e) {}//          Invoked when a key has been typed.

		BufferedImage img;
		int w() { return destimg.getWidth(); }
		int h() { return destimg.getHeight(); }
		int zw() { return destimg.getWidth() * zoom; }
		int zh() { return destimg.getHeight() * zoom; }
		int zoom = 3;
		
		public cimg(int w, int h) {
			img = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
		}
		
		int forcebar = 800; //force scrollbar
		public Dimension getMinimumSize() { return new Dimension(zw() + forcebar, zh() + forcebar); }
		public Dimension getPreferredSize() { return new Dimension(zw() + forcebar, zh() + forcebar); }
		public Dimension getMaximumSize() { return new Dimension(zw() + forcebar, zh() + forcebar); }
		
		//need .getViewport().setScrollMode(JViewport.SIMPLE_SCROLL_MODE);
		public void paint(Graphics g) {
			super.paint(g);
			Container c = getParent();
			JViewport v = (JViewport)c;
			JScrollPane s = (JScrollPane)v.getParent();
			
			int barx = s.getHorizontalScrollBar().getValue();
			int x = barx / zoom;

			//g.drawImage(img, 0,0,zw(),zh(), null);
			synchronized (destimg) {
				g.drawImage(destimg, 0,0,zw(),zh(), null);
			}
		}
	}
	



	public void linemix() {
		int w = srcimg.getWidth(), h = srcimg.getHeight();
		for (int y = 1 ;y < h; y++) {
			for (int x = 0; x < w; x++) {
				int rgb = srcimg.getRGB(x,y);
				double r = (rgb >> 16) & 0xff;
				double g = (rgb >> 8) & 0xff;
				double b = (rgb >> 0) & 0xff;
				double brightness = r * 0.299 + g * 0.587 + b * 0.114;
				if (r < 0.1) r = 0.1; //to get no div by 0 with black
				if (g < 0.1) g = 0.1; //to get no div by 0 with black
				if (b < 0.1) b = 0.1; //to get no div by 0 with black

				//get color part, crank up to full saturation
				double max = 0;
				if (r > max) max = r;
				if (g > max) max = g;
				if (b > max) max = b;
				double scale = 255.0 / max;
				double satr = r*scale;
				double satg = g*scale;
				double satb = b*scale;
				
				//data of previous line like on TV. I think taking next line would be wrong.
				int rgb2 = srcimg.getRGB(x,y - 1);
				double r2 = (rgb2 >> 16) & 0xff;	 
				double g2 = (rgb2 >> 8) & 0xff; 	 
				double b2 = (rgb2 >> 0) & 0xff;
				if (r2 < 0.1) r2 = 0.1; //to get no div by 0 with black
				if (g2 < 0.1) g2 = 0.1; //to get no div by 0 with black
				if (b2 < 0.1) b2 = 0.1; //to get no div by 0 with black

				//get color part, crank up to full saturation
				double max2 = 0;
				if (r2 > max2) max2 = r2;	
				if (g2 > max2) max2 = g2;	
				if (b2 > max2) max2 = b2;	
				double scale2 = 255.0 / max2;
				double satr2 = r2*scale2;
				double satg2 = g2*scale2;
				double satb2 = b2*scale2;
				
				//mix the two colors
				double r3 = (satr + satr2)/2.0;
				double g3 = (satg + satg2)/2.0;
				double b3 = (satb + satb2)/2.0;
				double brightness3 = r3 * 0.299 + g3 * 0.587 + b3 * 0.114;			
				
				//take mixcolor and tweak to original brightness
				r = r3*brightness/brightness3;
				g = g3*brightness/brightness3;
				b = b3*brightness/brightness3;
				
				//prevent overshooting beyond 255
				if (r > 255) r = 255;
				if (g > 255) g = 255;
				if (b > 255) b = 255;
				
				synchronized(destimg) { destimg.setRGB(x,y,((int)r*65536)+((int)g*256)+(int)b); }
			}
		}
	}

	BufferedImage destimg;
	BufferedImage srcimg;
	public void main2(String args[]) {
		srcimg = loadimage(new File("test.png"));
		destimg = loadimage(new File("test.png")); //for same dimension in that pic


		framelauncher f = new framelauncher(); 
		f.w = 640; f.h = 400;
		f.run();
		linemix();		
		f.f.repaint();
	}
	

}

p.s and no it is not dithering! I saw a solid plane of new color!

here's a test i did in the past, PAL TMS chip
http://imgur.com/XMlCZky

@Hit9918,

Wait, what's this you're saying about 2-color sprites?
Is that ALSO an MSX1-thing?
Got a piece of code you'd perhaps like to share?

Greetings,
Ron.

I remember there was some painting program already in the eighties for MSX1 that had the possibility to draw boxes with non-standard colors like brown using this technique. I don't remember the name of the program anymore but I recall it had a short opening music when it was started, a piece of "in the hall of the mountain king" from Peer Gynt.