CurvesImageOp.java

/*
 * Copyright (c) 2009 Piotr Piastucki
 * 
 * This file is part of Patchca CAPTCHA library.
 * 
 *  Patchca is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *  
 *  Patchca is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *  
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with Patchca. If not, see <http://www.gnu.org/licenses/>.
 */
package com.xiongyingqi.captcha.filter.library;

import com.xiongyingqi.captcha.color.ColorFactory;
import com.xiongyingqi.captcha.color.SingleColorFactory;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.Random;


public class CurvesImageOp extends AbstractImageOp {

    private float strokeMin;
    private float strokeMax;
    private ColorFactory colorFactory = new SingleColorFactory();

    public float getStrokeMin() {
        return strokeMin;
    }

    public void setStrokeMin(float strokeMin) {
        this.strokeMin = strokeMin;
    }

    public float getStrokeMax() {
        return strokeMax;
    }


    public void setStrokeMax(float strokeMax) {
        this.strokeMax = strokeMax;
    }

    public ColorFactory getColorFactory() {
        return colorFactory;
    }

    public void setColorFactory(ColorFactory colorFactory) {
        this.colorFactory = colorFactory;
    }

    private double hermiteSpline(double x1, double a1, double x2, double a2, double t) {
        double t2 = t * t;
        double t3 = t2 * t;
        double b = -a2 - 2.0 * a1 - 3.0 * x1 + 3.0 * x2;
        double a = a2 + a1 + 2.0 * x1 - 2.0 * x2;
        return a * t3 + b * t2 + a1 * t + x1;
    }

    private double catmullRomSpline(double x0, double x1, double x2, double x3, double t) {
        double a1 = (x2 - x0) / 2;
        double a2 = (x3 - x1) / 2;
        return hermiteSpline(x1, a1, x2, a2, t);
    }

    @Override
    public BufferedImage filter(BufferedImage src, BufferedImage dest) {
        if (dest == null) {
            dest = createCompatibleDestImage(src, null);
        }
        double width = dest.getWidth();
        double height = dest.getHeight();
        Graphics2D g2 = (Graphics2D) src.getGraphics();
        g2.setRenderingHints(new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON));
        Random r = new Random();
        int cp = 4 + r.nextInt(3);
        int[] xPoints = new int[cp];
        int[] yPoints = new int[cp];
        width -= 10;
        for (int i = 0; i < cp; i++) {
            xPoints[i] = (int) ((int) 5 + (i * width) / (cp - 1));
            yPoints[i] = (int) (height * (r.nextDouble() * 0.5 + 0.2));
        }
        int subsections = 6;
        int[] xPointsSpline = new int[(cp - 1) * subsections];
        int[] yPointsSpline = new int[(cp - 1) * subsections];
        for (int i = 0; i < cp - 1; i++) {
            double x0 = i > 0 ? xPoints[i - 1] : 2 * xPoints[i] - xPoints[i + 1];
            double x1 = xPoints[i];
            double x2 = xPoints[i + 1];
            double x3 = (i + 2 < cp) ? xPoints[i + 2] : 2 * xPoints[i + 1] - xPoints[i];
            double y0 = i > 0 ? yPoints[i - 1] : 2 * yPoints[i] - yPoints[i + 1];
            double y1 = yPoints[i];
            double y2 = yPoints[i + 1];
            double y3 = (i + 2 < cp) ? yPoints[i + 2] : 2 * yPoints[i + 1] - yPoints[i];
            for (int j = 0; j < subsections; j++) {
                xPointsSpline[i * subsections + j] = (int) catmullRomSpline(x0, x1, x2, x3, 1.0 / subsections * j);
                yPointsSpline[i * subsections + j] = (int) catmullRomSpline(y0, y1, y2, y3, 1.0 / subsections * j);
            }
        }
        for (int i = 0; i < xPointsSpline.length - 1; i++) {
            g2.setColor(colorFactory.getColor(i));
            g2.setStroke(new BasicStroke(2 + 2 * r.nextFloat()));
            g2.drawLine(xPointsSpline[i], yPointsSpline[i], xPointsSpline[i + 1], yPointsSpline[i + 1]);
        }
        return src;
    }
}