java图片生成等比例图片

最近在倒弄个一个网站，www.thinkdee.com  还在做，有一个上传图片LOGO需求，当然用户上传的图片不可能是原样输出的，这里要用等比例处理一下，不多说，附上代码：

package com.thinkdee.util;


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

import javax.imageio.ImageIO;

public class ScaleImage {

    public ScaleImage() {
        support = 3D;
        PI = 3.1415926535897798D;
    }


    /**
     * 
     * <b>Summary: </b>
     *     saveImageAsJpg(生成等比例图片)
     * @param fromFileStr
     * @param saveToFileStr
     * @param formatWideth
     * @param formatHeight
     * @throws Exception
     */
    public void saveImageAsJpg(String fromFileStr, String saveToFileStr,
            int formatWideth, int formatHeight) throws Exception {
        File saveFile = new File(saveToFileStr);
        File fromFile = new File(fromFileStr);
        BufferedImage srcImage = ImageIO.read(fromFile);
        int imageWideth = srcImage.getWidth(null);
        int imageHeight = srcImage.getHeight(null);
        int changeToWideth = 0;
        int changeToHeight = 0;
        if (imageWideth > 0 && imageHeight > 0)
            if (imageWideth / imageHeight >= formatWideth / formatHeight) {
                if (imageWideth > formatWideth) {
                    changeToWideth = formatWideth;
                    changeToHeight = (imageHeight * formatWideth) / imageWideth;
                } else {
                    changeToWideth = imageWideth;
                    changeToHeight = imageHeight;
                }
            } else if (imageHeight > formatHeight) {
                changeToHeight = formatHeight;
                changeToWideth = (imageWideth * formatHeight) / imageHeight;
            } else {
                changeToWideth = imageWideth;
                changeToHeight = imageHeight;
            }
        srcImage = imageZoomOut(srcImage, changeToWideth, changeToHeight);
        ImageIO.write(srcImage, "JPEG", saveFile);
    }

    public BufferedImage imageZoomOut(BufferedImage srcBufferImage, int w, int h) {
        width = srcBufferImage.getWidth();
        height = srcBufferImage.getHeight();
        scaleWidth = w;
        if (DetermineResultSize(w, h) == 1) {
            return srcBufferImage;
        } else {
            CalContrib();
            BufferedImage pbOut = HorizontalFiltering(srcBufferImage, w);
            BufferedImage pbFinalOut = VerticalFiltering(pbOut, h);
            return pbFinalOut;
        }
    }

    private int DetermineResultSize(int w, int h) {
        double scaleH = (double) w / (double) width;
        double scaleV = (double) h / (double) height;
        return scaleH < 1.0D || scaleV < 1.0D ? 0 : 1;
    }

    private double Lanczos(int i, int inWidth, int outWidth, double Support) {
        double x = ((double) i * (double) outWidth) / (double) inWidth;
        return ((Math.sin(x * PI) / (x * PI)) * Math.sin((x * PI) / Support))
                / ((x * PI) / Support);
    }

    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] = 1.0D;
        double weight = 0.0D;
        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 * 2D + 1.0D;
        for (i = 0; i <= center; i++)
            normContrib[i] = contrib[i] / weight;

        for (i = center + 1; i < nDots; i++)
            normContrib[i] = normContrib[center * 2 - i];

    }

    private void CalTempContrib(int start, int stop) {
        double weight = 0.0D;
        int i = 0;
        for (i = start; i <= stop; i++)
            weight += contrib[i];

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

    }

    private int GetRedValue(int rgbValue) {
        int temp = rgbValue & 0xff0000;
        return temp >> 16;
    }

    private int GetGreenValue(int rgbValue) {
        int temp = rgbValue & 0xff00;
        return temp >> 8;
    }

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

    private int ComRGB(int redValue, int greenValue, int blueValue) {
        return (redValue << 16) + (greenValue << 8) + blueValue;
    }

    private int HorizontalFilter(BufferedImage bufImg, int startX, int stopX,
            int start, int stop, int y, double pContrib[]) {
        double valueRed = 0.0D;
        double valueGreen = 0.0D;
        double valueBlue = 0.0D;
        int valueRGB = 0;
        int i = startX;
        for (int j = start; i <= stopX; j++) {
            valueRGB = bufImg.getRGB(i, y);
            valueRed += (double) GetRedValue(valueRGB) * pContrib[j];
            valueGreen += (double) GetGreenValue(valueRGB) * pContrib[j];
            valueBlue += (double) GetBlueValue(valueRGB) * pContrib[j];
            i++;
        }

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

    private BufferedImage HorizontalFiltering(BufferedImage bufImage, int iOutW) {
        int dwInW = bufImage.getWidth();
        int dwInH = bufImage.getHeight();
        int value = 0;
        BufferedImage pbOut = new BufferedImage(iOutW, dwInH, 1);
        for (int x = 0; x < iOutW; x++) {
            int X = (int) (((double) x * (double) dwInW) / (double) iOutW + 0.5D);
            int y = 0;
            int startX = X - nHalfDots;
            int start;
            if (startX < 0) {
                startX = 0;
                start = nHalfDots - X;
            } else {
                start = 0;
            }
            int stopX = X + nHalfDots;
            int stop;
            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;
    }

    private int VerticalFilter(BufferedImage pbInImage, int startY, int stopY,
            int start, int stop, int x, double pContrib[]) {
        double valueRed = 0.0D;
        double valueGreen = 0.0D;
        double valueBlue = 0.0D;
        int valueRGB = 0;
        int i = startY;
        for (int j = start; i <= stopY; j++) {
            valueRGB = pbInImage.getRGB(x, i);
            valueRed += (double) GetRedValue(valueRGB) * pContrib[j];
            valueGreen += (double) GetGreenValue(valueRGB) * pContrib[j];
            valueBlue += (double) GetBlueValue(valueRGB) * pContrib[j];
            i++;
        }

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

    private BufferedImage VerticalFiltering(BufferedImage pbImage, int iOutH) {
        int iW = pbImage.getWidth();
        int iH = pbImage.getHeight();
        int value = 0;
        BufferedImage pbOut = new BufferedImage(iW, iOutH, 1);
        for (int y = 0; y < iOutH; y++) {
            int Y = (int) (((double) y * (double) iH) / (double) iOutH + 0.5D);
            int startY = Y - nHalfDots;
            int start;
            if (startY < 0) {
                startY = 0;
                start = nHalfDots - Y;
            } else {
                start = 0;
            }
            int stopY = Y + nHalfDots;
            int stop;
            if (stopY > 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;
    }

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

    private int width;
    private int height;
    private int scaleWidth;
    double support;
    double PI;
    double contrib[];
    double normContrib[];
    double tmpContrib[];
    int startContrib;
    int stopContrib;
    int nDots;
    int nHalfDots;
}