Java Convert RGB (24 bit) to xterm-256 colors

Question

Java Convert RGB (24 bit) to xterm-256 colors. I see many posts on here but none for java. I look at python's code and lots of answers but they all don't do 6x6x6 cubes that tmux does. I don't understand c++ can someone please write tmux impl in java to convert RGB to xterm-256 color as a byte? And is this problematic in general. Should I be doing this at all? Should I say if the terminal doesn't support RGB to use 4 bit backup colors that people can easily understand.

Answer 1

use my Palette class. it can pick the closest color to the palette applicable. it requires a csv file <paletCode, name, R, G, B> and a library to parse a CSV file. from there you can use Palette#pickColor after it's been parsed

package jml.ot.colors;

import java.awt.Color;
import java.io.InputStream;
import java.util.LinkedHashSet;

import jredfox.common.config.csv.CSV;
import jredfox.common.config.csv.CSVE;

public class Palette {
    
    public LinkedHashSet<Entry> entries = new LinkedHashSet<Entry>();
    
    public Palette()
    {
        
    }
    
    /**
     * return the Palette's clostes color from RGB and then give you the Entry(code, name, rgb)
     */
    public Entry pickColor(Color c)
    {
        int d = 0;
        Palette.Entry picked = null;
        for(Palette.Entry e : this.entries)
        {
            int r = e.rgb.getRed();
            int g = e.rgb.getGreen();
            int b = e.rgb.getBlue();
            int distence = Math.abs(r - c.getRed()) + Math.abs(g - c.getGreen()) + Math.abs(b - c.getBlue());
            if(picked == null || distence < d)
            {
                d = distence;
                picked = e;
            }
        }
        return picked;
    }
    
    public Palette parse(InputStream in) throws Exception
    {
        CSVE ce = new CSVE();
        ce.parse(in);
        for(CSV c : ce.list)
            this.add(Integer.parseInt(c.list.get(0)), c.list.get(1), new Color(Integer.parseInt(c.list.get(2)), Integer.parseInt(c.list.get(3)), Integer.parseInt(c.list.get(4))));
        return this;
    }
    
    public void add(int code, String name, Color rgb)
    {
        this.entries.add(new Entry(code, name, rgb));
    }
    
    public void remove(int code)
    {
        this.entries.remove(new Entry(code, null, null));
    }
    
    public class Entry
    {
        public int code;
        public String name;
        public Color rgb;
        
        public Entry(int c, String n, Color color)
        {
            this.code = c;
            this.name = n;
            this.rgb = color;
        }
        
        @Override
        public int hashCode()
        {
            return this.code;
        }
        
        @Override
        public boolean equals(Object obj)
        {
            Entry o = (Entry)obj;
            return this.code == o.code;
        }
        
        @Override
        public String toString()
        {
            return this.code + ", " + this.name + ", " + this.rgb;
        }
    }

}