OCR.java

public class OCR {
	private static final String INPUT = "C:/captcha/ex.png";
	private static final String OUTPUT = "C:/captcha/captcha-out.png";
	private static final String TESSERACT_BIN = "C:/Program Files/Tesseract-OCR/tesseract.exe";
	private static final String TESSERACT_OUTPUT = "C:/captcha/out.txt";
	private static final int WHITE = 0x00FFFFFF, BLACK = 0x00000000;

	public static void main(String... args) throws Exception {
		BufferedImage image = ImageIO.read(new FileInputStream(INPUT));
		int average = 0;
		
		for( int row = 0; ++row < image.getHeight(); )
			for ( int column = 0; ++column < image.getWidth(); )
				average += image.getRGB(column, row) & 0x000000FF;
		average /= image.getWidth() * image.getHeight();
		
		for( int row = 0; ++row < image.getHeight(); )
			for ( int column = 0; ++column < image.getWidth(); )
				if ((image.getRGB(column, row) & 0x000000FF) <= average * .80)
					image.setRGB(column, row, BLACK);
				else
					image.setRGB(column, row, WHITE);
		
		for( int row = 0; ++row < image.getHeight(); )
			for ( int column = 0; ++column < image.getWidth(); )
				if ((image.getRGB(column, row) & WHITE) == WHITE) {
					int height = countVerticalWhite(image, column, row);
					int width = countHorizontalWhite(image, column, row);
					if ((width * height <= 6) || (width == 1) || (height == 1))
						image.setRGB(column, row, BLACK);
				}

		for( int row = 0; ++row < image.getHeight(); )
			for ( int column = 0; ++column < image.getWidth(); )
				if ((image.getRGB(column, row) & WHITE) != WHITE)
					if (countBlackNeighbors(image, column, row) <= 3)
						image.setRGB(column, row, WHITE);
		
		ImageIO.write(image, "png", new File(OUTPUT));
		Process tesseractProc = Runtime.getRuntime().exec(TESSERACT_BIN + " " + OUTPUT + " " + TESSERACT_OUTPUT + " nobatch letters");
		tesseractProc.waitFor();
		BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(TESSERACT_OUTPUT + ".txt")));
		System.out.println("CAPTCHA: " + reader.readLine());
		reader.close();
	}

        private static int countVerticalWhite(BufferedImage image, int x, int y) {
		return (countAboveWhite(image, x, y) + countBelowWhite(image, x, y)) + 1;
	}
	private static int countHorizontalWhite(BufferedImage image, int x, int y) {
		return (countLeftWhite(image, x, y) + countRightWhite(image, x, y)) + 1;
	}
	private static int countLeftWhite(BufferedImage image, int x, int y) {
		int leftWhite = 0;
		x--;
		while (x-- > 0)
			if ((image.getRGB(x, y) & WHITE) == WHITE)
				leftWhite++;
			else
				break;
		return leftWhite;
	}
	private static int countRightWhite(BufferedImage image, int x, int y) {
		int rightWhite = 0;
		x++;
		while (x < image.getWidth())
			if ((image.getRGB(x++, y) & WHITE) == WHITE)
				rightWhite++;
			else
				break;
		return rightWhite;
	}
	private static int countBlackNeighbors(BufferedImage image, int x, int y) {
		int numBlacks = 0;
		if (pixelColor(image, x - 1, y) != WHITE)
			numBlacks++;
		if (pixelColor(image, x - 1, y + 1) != WHITE)
			numBlacks++;
		if (pixelColor(image, x - 1, y - 1) != WHITE)
			numBlacks++;
		if (pixelColor(image, x, y + 1) != WHITE)
			numBlacks++;
		if (pixelColor(image, x, y - 1) != WHITE)
			numBlacks++;
		if (pixelColor(image, x + 1, y) != WHITE)
			numBlacks++;
		if (pixelColor(image, x + 1, y + 1) != WHITE)
			numBlacks++;
		if (pixelColor(image, x + 1, y - 1) != WHITE)
			numBlacks++;
		return numBlacks;
	}
	private static int pixelColor(BufferedImage image, int x, int y) {
		if (x >= image.getWidth() || x < 0 || y < 0 || y >= image.getHeight())
			return WHITE;
		return image.getRGB(x, y) & WHITE;
	}
}