/*
* Copyright 1999-2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.cocoon.reading;
import java.awt.Color;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.awt.image.WritableRaster;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.Random;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGEncodeParam;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
/**
* <p>The {@link CaptchaReader} is a simple tool generating JPEG images for the text
* supplied as its source in a way so that it's hard to parse automatically.</p>
*
* <p><i>CAPTCHA</i> means quite literally <i>Completely Automated Public Turing
* Test to Tell Computers and Humans Apart</i> and one of the best resources on
* this can be found at the <a href="http://www.captcha.net/">Carnegie Mellon
* School of Computer Science CAPTCHA project.</a>.
*
* <p>This reader creates very simple <i>CAPTCHAs</i> from within a Cocoon pipeline,
* enabling quick and safe end-user presence identificat. As an example, look at the
* following pipeline snippet:</p>
*
* <pre>
* <map:match pattern="*">
* <map:read type="captcha" src="{1}"/>
* </map:match>
* </pre>
*
* <p>The example will produce an image containing the text in <code>{1}</code>
* "warped" or "bent" in a way similar to the Adobe® Photoshop® "Wave"
* filter plugin.</p>
*
* <p>Few pipeline parameters control the operation of the {@link CaptchaReader}
* (this component is not configurable):</p>
*
* <ul>
* <li><code>width</code>: the width of the image to generate (default: 100).</li>
* <li><code>height</code>: the height of the image to generate (default: 50).</li>
* <li><code>foreground</code>: the text foreground color (default: random).</li>
* <li><code>background</code>: the image background color (default: white).</li>
* <li><code>font</code>: the font to use for the text (default: serif).</li>
* <li><code>scale</code>: the scaling factor for interim images (default: 5).</li>
* <li><code>amount</code>: the amount of text warping to apply (default: 1).</li>
* <li><code>quality</code>: the JPEG encoding quality (default: 0.75).</li>
* </ul>
*
* <p>Note that when the <code>foreground</code> parameter is not specified, the
* color used to write the text will be randomly chosen in a way that it contrasts
* well with the background color to avoid problems of illegible text.</p>
*
* <p>Both the <code>foreground</code> and <code>background</code> parameters accept
* strings in the format specified by {@link Color#decode(String)} (for example
* <code>fff</code>, or <code>0099CC</code>) or one of the field names of the
* {@link Color} class (for example {@link Color#BLACK BLACK} or {@link Color#cyan
* cyan} ...).</p>
*
* <p>The <code>scale</code> parameter controls how much the specified size should
* be scaled while processing the interim images: the bigger the scaling factor, the
* better the image quality, but also the memory used while generating the final
* image will be bigger. In other words, use with care.</p>
*
* <p>The <code>amount</code> parameter is interpreted as a floating point number
* and must be greater than zero. This controls how much text should be warped, and
* normally a value of <code>1</code> produce quite-good warping. Increasing (or
* decreasing) this value will produce more (ore less) warping.</p>
*
* <p>Remember that in no way the {@link CaptchaReader} claims to be able to
* generate "unbreakable" text (that will be impossible), and improvements to the
* algorithm are welcome.</p>
*
*/
public class CaptchaReader extends AbstractReader {
/** <p>A unique {@link Random} instance to use.</p> */
private static final Random RANDOM = new Random();
/**
* <p>The content type of the generated content: <code>image/jpeg</code>.</p>
*
* @return Always <code>image/jpeg</code>.
*/
public String getMimeType() {
return "image/jpeg";
}
/**
* <p>Return a {@link Color} instance from a specified parameter.</p>
*
* @param parameterName The name of the parameter whose to use as the color.
* @param defaultColor The default {@link Color} to return.
* @return the interpreted color or the default color specified.
*/
private Color getColor(String parameterName, Color defaultColor) {
String colorString = this.parameters.getParameter(parameterName, null);
if (colorString == null) return defaultColor;
try {
return Color.decode(colorString);
} catch (Exception e1) {
try {
Field colorField = Color.class.getDeclaredField(colorString);
return (Color) colorField.get(Color.class);
} catch (Exception e2) {
return defaultColor;
}
}
}
private Graphics2D antialiasedGraphics(BufferedImage image) {
Graphics2D graphics = image.createGraphics();
graphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
return graphics;
}
/**
* <p>Create an image containing the text specified as this reader source
* warped to avoid automatic interpretation.</p>
*
* @throws IOException if an I/O error occurred generating the image.
*/
public void generate()
throws IOException {
/* Retrieve the current operational parameters from Cocoon's sitemap */
final int width = this.parameters.getParameterAsInteger("width", 100);
final int height = this.parameters.getParameterAsInteger("height", 50);
Color background = this.getColor("background", Color.white);
Color foreground = this.getColor("foreground", null);
if (foreground == null) {
int r = (RANDOM.nextInt(64) + 96 + background.getRed()) & 0x0ff;
int g = (RANDOM.nextInt(64) + 96 + background.getGreen()) & 0x0ff;
int b = (RANDOM.nextInt(64) + 96 + background.getBlue()) & 0x0ff;
foreground = new Color(r, g, b);
}
final String fontName = this.parameters.getParameter("font", "serif");
final int scale = this.parameters.getParameterAsInteger("scale", 5);
final float amount = this.parameters.getParameterAsFloat("amount", 2);
final float quality = this.parameters.getParameterAsFloat("quality", 0.75F);
final String text = this.source;
/* Create the final buffered image we will be writing to at the bottom */
final BufferedImage result = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
/* Starting with a size of 100, evaluate how big the real font should be */
final Font baseFont = new Font(fontName, Font.PLAIN, 100);
final Graphics2D graphics = this.antialiasedGraphics(result);
final FontMetrics metrics = graphics.getFontMetrics(baseFont);
final Rectangle2D tempSize = metrics.getStringBounds(text, graphics);
/* Evaluate the image size of the resulting image and prepare a ratio */
final double tempWidth = tempSize.getWidth() + (2 * tempSize.getHeight());
final double tempHeight = (tempSize.getHeight() * (1 + amount));
final double ratioWidth = width * scale / tempWidth;
final double ratioHeight = height * scale / tempHeight;
final double ratio = ratioWidth < ratioHeight? ratioWidth: ratioHeight;
final Font font = baseFont.deriveFont((float) (100 * ratio));
/* Evaluate the final size of the text to write */
final FontMetrics sourceMetrics = graphics.getFontMetrics(font);
final Rectangle2D size = sourceMetrics.getStringBounds(text, graphics);
final double textWidth = size.getWidth();
final double textHeight = size.getHeight();
/* Evaluate the final size of the interim images */
int scaledWidth = (int) (tempWidth * ratio);
int scaledHeight = (int) (tempHeight * ratio);
/* Create a couple of images to write the plain string and the warped one */
BufferedImage source = new BufferedImage(scaledWidth, scaledHeight,
BufferedImage.TYPE_BYTE_GRAY);
BufferedImage warped = new BufferedImage(scaledWidth, scaledHeight,
BufferedImage.TYPE_INT_ARGB);
/* Prepare the background and the font of the source image */
final Graphics2D sourceGraphics = this.antialiasedGraphics(source);
sourceGraphics.setColor(Color.black);
sourceGraphics.fillRect(0, 0, scaledWidth, scaledHeight);
sourceGraphics.setFont(font);
/* Write the string exactly in the middle of the source image */
float textX = (float) ((scaledWidth - textWidth) / 2);
float textY = (float) ((scaledHeight - textHeight) / 2);
sourceGraphics.setColor(Color.white);
sourceGraphics.drawString(text, textX, textY + sourceMetrics.getAscent());
/* Randomize displacement factors for sine-waves */
final int displaceTop = RANDOM.nextInt(scaledWidth);
final int displaceBtm = RANDOM.nextInt(scaledWidth);
final int displaceVer = RANDOM.nextInt(scaledHeight);
/* Calculate the horizontal and vertical amplitude and wavelength of sines */
final double amplitHor = textHeight * amount / 4;
final double amplitVer = textHeight / 8;
final double t = (RANDOM.nextDouble() * textWidth / 2) + (textWidth * 0.75);
final double b = (RANDOM.nextDouble() * textWidth / 2) + (textWidth * 0.75);
final double wlenTop = textHeight > t? textHeight: t;
final double wlenBtm = textHeight > b? textHeight: b;
/* Calculate the offsets for horizontal (top and bottom) sine waves */
final double offsetTop = amplitHor;
final double offsetBtm = scaledHeight - amplitHor;
/* Prepare an array for vertical displacement sine wave */
final double vert[] = new double[scaledHeight];
for (int v = 0; v < scaledHeight ; v++) {
vert[v] = Math.sin((Math.PI * (v + displaceVer)) / textHeight) * amplitVer;
}
/* Iterate all the target image pixels and render the distortion */
int x1 = Integer.MAX_VALUE;
int x2 = Integer.MIN_VALUE;
int y1 = Integer.MAX_VALUE;
int y2 = Integer.MIN_VALUE;
final WritableRaster sourceRaster = source.getRaster();
final WritableRaster warpedRaster = warped.getRaster();
final double src[] = new double[9];
final double col[] = new double[] { foreground.getRed(),
foreground.getGreen(),
foreground.getBlue(), 0};
for (int h = 0; h < scaledWidth; h++) {
final double baseTop = (Math.PI * (h + displaceTop)) / wlenTop;
final double baseBtm = (Math.PI * (h + displaceBtm)) / wlenBtm;
final double top = offsetTop + Math.sin(baseTop) * amplitHor;
final double btm = offsetBtm - Math.sin(baseBtm) * amplitHor;
for (int v = 0; v < scaledHeight; v ++) {
final double x = (h + vert[v]);
final double y = (v * ((btm - top) / scaledHeight)) + top;
if ((y > 0) && (y < scaledHeight - 1) &&
(x > 0) && (x < scaledWidth - 1)) {
/* Retrieve the nine pixels around the source one */
sourceRaster.getPixels((int)(x-1), (int)(y-1), 3, 3, src);
/* Average their value (it's grayscale) to have a better warp */
double alpha = ((src[1] + src[3] + src[5] + src[7]) * 0.1) +
((src[0] + src[2] + src[6] + src[8]) * 0.025) +
(src[4] * 0.5);
/* Write the resultin pixel in the target image if necessary */
if (alpha > 0) {
col[3] = alpha;
warpedRaster.setPixel(h, v, col);
if (h < x1) x1 = h;
if (h > x2) x2 = h;
if (v < y1) y1 = v;
if (v > y2) y2 = v;
}
}
}
}
/* Crop the image to the maximum extent of the warped text (if visible) */
source = null;
int xd = x2 - x1 + 1;
int yd = y2 - y1 + 1;
if ((xd > 1) && (yd > 1)) {
warped = warped.getSubimage(x1, y1, xd, yd);
}
/* Rescale the cropped image to the required size */
Image image = warped.getScaledInstance(width, height, Image.SCALE_SMOOTH);
graphics.setBackground(background);
graphics.setColor(background);
graphics.fillRect(0, 0, width, height);
graphics.setColor(foreground);
graphics.drawImage(image, 0, 0, null);
warped = null;
/* Write the processed image as a JPEG image */
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(buffer);
JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(result);
param.setQuality(quality, true);
encoder.encode(result, param);
buffer.flush();
buffer.close();
this.out.write(buffer.toByteArray());
this.out.flush();
}
}