Histrogram

Main.java

package xyz.mycharlie.colourhistogram;

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

public class Main {
	public int[][] createRGBData(BufferedImage img) {
		int[] R=new int[256], G=new int[256], B=new int[256];
		
		for(int x=0; x<img.getWidth(); x++) {
			for(int y=0; y<img.getHeight(); y++) {
				
				int c = img.getRGB(x, y);
				int r = (c & 0xff0000) >> 16,
					g = (c & 0xff00  ) >> 8,
					b = (c & 0xff    ) >> 0;
				
				R[r]++;
				G[g]++;
				B[b]++;
			}
		}
		
		
		return new int[][]{R, G, B};
	}
	
	public BufferedImage createImage(int[] data, char colour) {
		int MAX_Y=128;
		
		// Get max
		double max=0;
		for(int i=1; i<data.length; i++)
			if(data[i]>max)
				max=data[i];
		
		BufferedImage img = new BufferedImage(data.length, MAX_Y+1, BufferedImage.TYPE_3BYTE_BGR);
		
		// TODO: Set white background on left side, and black background on right side
		
		int r = (colour=='r' || colour=='G') ? 1 : 0,
			g = (colour=='g' || colour=='G') ? 1 : 0,
			b = (colour=='b' || colour=='G') ? 1 : 0;
		
		for(int x=1; x<data.length; x++) {
			int c = new Color(x*r, x*g, x*b).getRGB();
			
			// Line from (x, MAX_Y) to (x, data[x]/max*MAX_Y),
			// horizontally reversed so the line goes from bottom to top
			double end = MAX_Y - data[x] / max * MAX_Y;
			for(int y=MAX_Y; y > end; y--) {
				img.setRGB(x, y, c);
			}
		}
		
		return img;
	}
	
	public Main(String[] args) {
		String filename = "LARGE.png";
		
		// Parse arguments
		for(int i=0; i<args.length; i++) {
			String arg = args[i];
			
			switch(arg) {
			case "--file": case "-f":
				filename=args[++i];
				break;
				
			default:
				System.err.println("Unknown argument '"+arg+"'.");
			}
		}
		
		
		// Create
		try {
			System.out.println("Reading image");
			BufferedImage img = ImageIO.read(new File(filename));
			
			System.out.println("Collecting data");
			int[][] data = createRGBData(img);
			
			System.out.println("Creating images");
			
			BufferedImage red = createImage(data[0], 'r');
			BufferedImage green = createImage(data[1], 'g');
			BufferedImage blue = createImage(data[2], 'b');
			BufferedImage grey = createImage(data[2], 'G');
			
			System.out.println("Writing images");
			
			System.out.println("- Red");
			ImageIO.write(red, "png", new File("red.png"));
			System.out.println("- Green");
			ImageIO.write(green, "png", new File("green.png"));
			System.out.println("- Blue");
			ImageIO.write(blue, "png", new File("blue.png"));
			System.out.println("- Grey");
			ImageIO.write(grey, "png", new File("grey.png"));
			
			System.out.println("Done");
		} catch(Exception e) {
			e.printStackTrace(System.out);
		}
	}
	
	public static Main main;
	public static void main(String[] args) {
		main = new Main(args);
	}
}