JAVA图像缩放处理

http://www.blogjava.net/kinkding/archive/2009/05/23/277552.html

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今天在网上看到了一篇关于JAVA图像处理的文章，博主贴出了一个处理类：特点是高品质缩小，具体代码如下：

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

import javax.imageio.ImageIO;

public class ImageScale {

    private int width;
    private int height;
    private int scaleWidth;
    double support = (double) 3.0;
    double[] contrib;
    double[] normContrib;
    double[] tmpContrib;
    int startContrib, stopContrib;
    int nDots;
    int nHalfDots;

    public BufferedImage imageZoomOut(BufferedImage srcBufferImage, int w, int h, boolean lockScale) {
        width = srcBufferImage.getWidth();
        height = srcBufferImage.getHeight();
        scaleWidth = w;
        if (lockScale) {
            h = w * height / width;
        }

        if (DetermineResultSize(w, h) == 1) {
            return srcBufferImage;
        }
        CalContrib();
        BufferedImage pbOut = HorizontalFiltering(srcBufferImage, w);
        BufferedImage pbFinalOut = VerticalFiltering(pbOut, h);
        return pbFinalOut;
    }

    /**
     * 决定图像尺寸
     */
    private int DetermineResultSize(int w, int h) {
        double scaleH, scaleV;
        scaleH = (double) w / (double) width;
        scaleV = (double) h / (double) height;
        // 需要判断一下scaleH，scaleV，不做放大操作
        if (scaleH >= 1.0 && scaleV >= 1.0) {
            return 1;
        }
        return 0;

    } // end of DetermineResultSize()

    private double Lanczos(int i, int inWidth, int outWidth, double Support) {
        double x;

        x = (double) i * (double) outWidth / (double) inWidth;

        return Math.sin(x * Math.PI) / (x * Math.PI) * Math.sin(x * Math.PI / Support) / (x * Math.PI / Support);

    } // end of Lanczos()

    //
    // Assumption: same horizontal and vertical scaling factor
    //
    private void CalContrib() {
        nHalfDots = (int) ((double) width * support / (double) scaleWidth);
        nDots = nHalfDots * 2 + 1;
        try {
            contrib = new double[nDots];
            normContrib = new double[nDots];
            tmpContrib = new double[nDots];
        } catch (Exception e) {
            System.out.println("init contrib,normContrib,tmpContrib" + e);
        }

        int center = nHalfDots;
        contrib[center] = 1.0;

        double weight = 0.0;
        int i = 0;
        for (i = 1; i <= center; i++) {
            contrib[center + i] = Lanczos(i, width, scaleWidth, support);
            weight += contrib[center + i];
        }

        for (i = center - 1; i >= 0; i--) {
            contrib[i] = contrib[center * 2 - i];
        }

        weight = weight * 2 + 1.0;

        for (i = 0; i <= center; i++) {
            normContrib[i] = contrib[i] / weight;
        }

        for (i = center + 1; i < nDots; i++) {
            normContrib[i] = normContrib[center * 2 - i];
        }
    } // end of CalContrib()

    // 处理边缘
    private void CalTempContrib(int start, int stop) {
        double weight = 0;

        int i = 0;
        for (i = start; i <= stop; i++) {
            weight += contrib[i];
        }

        for (i = start; i <= stop; i++) {
            tmpContrib[i] = contrib[i] / weight;
        }

    } // end of CalTempContrib()

    private int GetRedValue(int rgbValue) {
        int temp = rgbValue & 0x00ff0000;
        return temp >> 16;
    }

    private int GetGreenValue(int rgbValue) {
        int temp = rgbValue & 0x0000ff00;
        return temp >> 8;
    }

    private int GetBlueValue(int rgbValue) {
        return rgbValue & 0x000000ff;
    }

    private int ComRGB(int redValue, int greenValue, int blueValue) {

        return (redValue << 16) + (greenValue << 8) + blueValue;
    }

    // 行水平滤波
    private int HorizontalFilter(BufferedImage bufImg, int startX, int stopX, int start, int stop, int y,
            double[] pContrib) {
        double valueRed = 0.0;
        double valueGreen = 0.0;
        double valueBlue = 0.0;
        int valueRGB = 0;
        int i, j;

        for (i = startX, j = start; i <= stopX; i++, j++) {
            valueRGB = bufImg.getRGB(i, y);

            valueRed += GetRedValue(valueRGB) * pContrib[j];
            valueGreen += GetGreenValue(valueRGB) * pContrib[j];
            valueBlue += GetBlueValue(valueRGB) * pContrib[j];
        }

        valueRGB = ComRGB(Clip((int) valueRed), Clip((int) valueGreen), Clip((int) valueBlue));
        return valueRGB;

    } // end of HorizontalFilter()

    // 图片水平滤波
    private BufferedImage HorizontalFiltering(BufferedImage bufImage, int iOutW) {
        int dwInW = bufImage.getWidth();
        int dwInH = bufImage.getHeight();
        int value = 0;
        BufferedImage pbOut = new BufferedImage(iOutW, dwInH, BufferedImage.TYPE_INT_RGB);

        for (int x = 0; x < iOutW; x++) {

            int startX;
            int start;
            int X = (int) (((double) x) * ((double) dwInW) / ((double) iOutW) + 0.5);
            int y = 0;

            startX = X - nHalfDots;
            if (startX < 0) {
                startX = 0;
                start = nHalfDots - X;
            } else {
                start = 0;
            }

            int stop;
            int stopX = X + nHalfDots;
            if (stopX > (dwInW - 1)) {
                stopX = dwInW - 1;
                stop = nHalfDots + (dwInW - 1 - X);
            } else {
                stop = nHalfDots * 2;
            }

            if (start > 0 || stop < nDots - 1) {
                CalTempContrib(start, stop);
                for (y = 0; y < dwInH; y++) {
                    value = HorizontalFilter(bufImage, startX, stopX, start, stop, y, tmpContrib);
                    pbOut.setRGB(x, y, value);
                }
            } else {
                for (y = 0; y < dwInH; y++) {
                    value = HorizontalFilter(bufImage, startX, stopX, start, stop, y, normContrib);
                    pbOut.setRGB(x, y, value);
                }
            }
        }

        return pbOut;

    } // end of HorizontalFiltering()

    private int VerticalFilter(BufferedImage pbInImage, int startY, int stopY, int start, int stop, int x,
            double[] pContrib) {
        double valueRed = 0.0;
        double valueGreen = 0.0;
        double valueBlue = 0.0;
        int valueRGB = 0;
        int i, j;

        for (i = startY, j = start; i <= stopY; i++, j++) {
            valueRGB = pbInImage.getRGB(x, i);

            valueRed += GetRedValue(valueRGB) * pContrib[j];
            valueGreen += GetGreenValue(valueRGB) * pContrib[j];
            valueBlue += GetBlueValue(valueRGB) * pContrib[j];
        }

        valueRGB = ComRGB(Clip((int) valueRed), Clip((int) valueGreen), Clip((int) valueBlue));
        // System.out.println(valueRGB);
        return valueRGB;

    } // end of VerticalFilter()

    private BufferedImage VerticalFiltering(BufferedImage pbImage, int iOutH) {
        int iW = pbImage.getWidth();
        int iH = pbImage.getHeight();
        int value = 0;
        BufferedImage pbOut = new BufferedImage(iW, iOutH, BufferedImage.TYPE_INT_RGB);

        for (int y = 0; y < iOutH; y++) {

            int startY;
            int start;
            int Y = (int) (((double) y) * ((double) iH) / ((double) iOutH) + 0.5);

            startY = Y - nHalfDots;
            if (startY < 0) {
                startY = 0;
                start = nHalfDots - Y;
            } else {
                start = 0;
            }

            int stop;
            int stopY = Y + nHalfDots;
            if (stopY > (int) (iH - 1)) {
                stopY = iH - 1;
                stop = nHalfDots + (iH - 1 - Y);
            } else {
                stop = nHalfDots * 2;
            }

            if (start > 0 || stop < nDots - 1) {
                CalTempContrib(start, stop);
                for (int x = 0; x < iW; x++) {
                    value = VerticalFilter(pbImage, startY, stopY, start, stop, x, tmpContrib);
                    pbOut.setRGB(x, y, value);
                }
            } else {
                for (int x = 0; x < iW; x++) {
                    value = VerticalFilter(pbImage, startY, stopY, start, stop, x, normContrib);
                    pbOut.setRGB(x, y, value);
                }
            }

        }

        return pbOut;

    } // end of VerticalFiltering()

    int Clip(int x) {
        if (x < 0)
            return 0;
        if (x > 255)
            return 255;
        return x;
    }

    public static void main(String[] args) throws IOException {
        ImageScale is = new ImageScale();
        String path = "D:\My Documents\My Pictures\pictrue\";
        BufferedImage image1 = ImageIO.read(new File(path + "test.jpg"));
        int w = 200, h = 400;
        BufferedImage image2 = is.imageZoomOut(image1, w, h, true);
        FileOutputStream out = new FileOutputStream(path + "test_2.jpg");
        ImageIO.write(image2, "jpeg", out);
    }
}

 

上面的代码中，本人做了一点小改进：imageZoomOut方法中，添加了一个lockScale参数，如果为true则表明保持纵横比。
程序运行的效果如下：
test.jpg（原图）：


test_2.jpg（程序生成的图片）：