How to remove lines in any orientation from an image

Basically i wish to remove lines that possib开发者_StackOverflow中文版ly overlay text such as those typically found in a captcha text image, so the after image contains only the text. Any suggestions on how to solve this problem will be appreciated.

Do you want to edit existing captcha image generator (which would be hard because it may relate to particular captcha implementation, and you don't disclose the implementation codes here), or do you want to generate a new captcha (which looks smooth and clean, without overlay text)?

Here is what I did when I created my own captcha for my JSP web application page. You will have to remove the JSP import statements, and replace that with JAVA import statements. You can freely edit the code and generate your own captcha (edit the graphics) if you want. Hope this helps !

<%@ page import="java.util.*"%>
<%@ page import="java.io.*"%>
<%@ page import="javax.servlet.*"%>
<%@ page import="javax.servlet.http.*"%>
<%@ page import="java.awt.*"%>
<%@ page import="java.awt.image.*"%>
<%@ page import="javax.imageio.*"%>
<%@ page import="java.awt.geom.*"%>
<%
   response.setContentType("image/jpg");

  try {

        Color backgroundColor = Color.green;
        Color borderColor = Color.orange;
        Color textColor = Color.white;
        Color circleColor = Color.green;
        Font textFont = new Font("Arial", Font.PLAIN, 24);
        int charsToPrint = 6;
        int width = request.getParameter("width") != null ? Integer.parseInt(request.getParameter("width")) : 150;
        int height = request.getParameter("height") != null ? Integer.parseInt(request.getParameter("height")) : 80;
        int circlesToDraw = 6;
        float horizMargin = 20.0f;
        float imageQuality = 0.95f; // max is 1.0 (this is for jpeg)
        double rotationRange = 0.7; // this is radians
        BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        Graphics2D g = (Graphics2D) bufferedImage.getGraphics();

        //Draw an oval
        g.setColor(Color.DARK_GRAY);
        g.fillRect(0, 0, width, height);

        // lets make some noisey circles
        g.setColor(circleColor);
        for ( int i = 0; i < circlesToDraw; i++ ) {
             int circleRadius = (int) (Math.random() * height / 2.0);
             int circleX = (int) (Math.random() * width - circleRadius);
             int circleY = (int) (Math.random() * height - circleRadius);
             g.drawOval(circleX, circleY, circleRadius * 2, circleRadius * 2);
        }

        g.setColor(textColor);
        g.setFont(textFont);

        FontMetrics fontMetrics = g.getFontMetrics();
        int maxAdvance = fontMetrics.getMaxAdvance();
        int fontHeight = fontMetrics.getHeight();

        // i removed 1 and l and i because there are confusing to users...
        // Z, z, and N also get confusing when rotated
        // 0, O, and o are also confusing...
        // lowercase G looks a lot like a 9 so i killed it
        // this should ideally be done for every language...
        // i like controlling the characters though because it helps prevent confusion
        String elegibleChars = "ABCDEFGHJKLMPQRSTUVWXYabcdefhjkmnpqrstuvwxy23456789";
        char[] chars = elegibleChars.toCharArray();

        float spaceForLetters = -horizMargin * 2 + width;
        float spacePerChar = spaceForLetters / (charsToPrint - 1.0f);

        AffineTransform transform = g.getTransform();

        StringBuffer finalString = new StringBuffer();

        for ( int i = 0; i < charsToPrint; i++ ) {
            double randomValue = Math.random();
            int randomIndex = (int) Math.round(randomValue * (chars.length - 1));
            char characterToShow = chars[randomIndex];
            finalString.append(characterToShow);

            // this is a separate canvas used for the character so that
            // we can rotate it independently
            int charImageWidth = maxAdvance * 2;
            int charImageHeight = fontHeight * 2;
            int charWidth = fontMetrics.charWidth(characterToShow);
            int charDim = Math.max(maxAdvance, fontHeight);
            int halfCharDim = (int) (charDim / 2);

            BufferedImage charImage = new BufferedImage(charDim, charDim, BufferedImage.TYPE_INT_ARGB);
            Graphics2D charGraphics = charImage.createGraphics();
            charGraphics.translate(halfCharDim, halfCharDim);
            double angle = (Math.random() - 0.5) * rotationRange;
            charGraphics.transform(AffineTransform.getRotateInstance(angle));
            charGraphics.translate(-halfCharDim,-halfCharDim);
            charGraphics.setColor(textColor);
            charGraphics.setFont(textFont);

            int charX = (int) (0.5 * charDim - 0.5 * charWidth);
            charGraphics.drawString("" + characterToShow, charX,(int) ((charDim - fontMetrics.getAscent()) / 2 + fontMetrics.getAscent()));

            float x = horizMargin + spacePerChar * (i) - charDim / 2.0f;
            int y = (int) ((height - charDim) / 2);

            g.drawImage(charImage, (int) x, y, charDim, charDim, null, null);

            charGraphics.dispose();
        }

        //Write the image as a jpg
        Iterator iter = ImageIO.getImageWritersByFormatName("JPG");
        if( iter.hasNext() ) {
            ImageWriter writer = (ImageWriter)iter.next();
            ImageWriteParam iwp = writer.getDefaultWriteParam();
            iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
            iwp.setCompressionQuality(imageQuality);
            writer.setOutput(ImageIO.createImageOutputStream(response.getOutputStream()));
            IIOImage imageIO = new IIOImage(bufferedImage, null, null);
            writer.write(null, imageIO, iwp);
        } else {
            throw new RuntimeException("no encoder found for jsp");
        }

        // let's stick the final string in the session (optional, only if you use JSP session object, and want to save it inside the user session)
        session.setAttribute("captcha", finalString.toString());

        g.dispose();
    }
    catch (IOException ioe) {
            throw new RuntimeException("Unable to build image" , ioe);
    }
%>