OCRPrep Code

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

// assumptions:
// white is white
// lines orthogonal

public class Chopper {
	// needs to be parameterized
	// a function to find the local minimum
	static double wthresh = 8.2;

	public static void main(String args[]) {
		try {
			if (args.length != 1)
				throw new Exception("usage: java Chopper <input>");
			File od = new File("chopped");
			if (! od.exists()) {
				od.mkdir();
			}
			else if (! od.isDirectory()) {
				throw new Exception("output directory obstructed");
			}
			else {
				File list[] = od.listFiles();
				for (File f : list) {
					f.delete();
				}
			}
			Chopper c = new Chopper(ImageIO.read(new File(args[0])));
			c.dump();
		} catch (Throwable t) {
			System.err.println(t);
			System.exit(1);
		}
	}

	BufferedImage image;
	LinkedList<Rectangle> rl;
	Chopper(BufferedImage _image) {
		image = _image;
		rl = new LinkedList<Rectangle>();
		chop();
	}

	void chop() {
		int y;
		boolean region;
		Rectangle linerect = new Rectangle(0, 0, image.getWidth(), 0);

		// never a row of i's or :'s, etc
		for (y = 0, region = false; y < image.getHeight(); y++) {
			if (region) {
				if (isLineWhite(y)) {
					region = false;
					linerect.height = y - linerect.y;
					chop(linerect);
				}
			}
			else {
				if (! isLineWhite(y)) {
					region = true;
					linerect.y = y;
				}
			}
		}
	}

	void chop(Rectangle linerect) {
		int x, y;
		boolean region;
		Rectangle r = new Rectangle(0, linerect.y, 0, linerect.height);

		for (x = 0, region = false; x < image.getWidth(); x++) {
			if (region) {
				if (isSubcolWhite(x, linerect.y, linerect.height)) {
					region = false;
					r.width = x - r.x;
					rl.add(new Rectangle(r));
				}
			}
			else {
				if (! isSubcolWhite(x, linerect.y, linerect.height)) {
					region = true;
					r.x = x;
				}
			}
		}
	}

	boolean isLineWhite(int y) {
		int rgb;
		int w = image.getWidth();
		double dw = 0.0;

		for (int x = 0; x < w; x++) {
			rgb = image.getRGB(x, y);
			int rd = 0xff - ((rgb & 0xff0000) >> 16);
			int gd = 0xff - ((rgb & 0xff00) >> 8);
			int bd = 0xff - (rgb & 0xff);
			dw += Math.sqrt(rd*rd + gd*gd + bd*bd) / (double)w;
		}
		return dw < wthresh;
	}

	boolean isSubcolWhite(int x, int y, int h) {
		int rgb;
		double dw = 0.0;

		for (int y1 = y; y1 < y+h; y1++) {
			rgb = image.getRGB(x, y1);
			int rd = 0xff - ((rgb & 0xff0000) >> 16);
			int gd = 0xff - ((rgb & 0xff00) >> 8);
			int bd = 0xff - (rgb & 0xff);
			dw += Math.sqrt(rd*rd + gd*gd + bd*bd) / (double)h;
		}
		return dw < wthresh;
	}

	void dump() throws Throwable {
		int counter = 0;
		int digits = (int)Math.floor(Math.log10((double)rl.size())) + 1;
		for (Rectangle r : rl) {
			ImageIO.write(
					image.getSubimage(r.x, r.y, r.width, r.height), "PNG",
					new File(
						"chopped" + File.separator +
						lzpad(Integer.toString(counter++), digits) + ".png"));
		}
	}

	String lzpad(String x, int y) {
		String pad = "";
		for (int i = 0; i < y - x.length(); i++) {
			pad += '0';
		}
		return pad + x;
	}
}