本文实例讲述了java生成缩略图的方法。分享给大家供大家参考，具体如下：

package com.util;import java.awt.image.BufferedImage;import java.io.File;import java.io.IOException;import javax.imageio.ImageIO;/*** 生成压缩图**/public class ImageScale {private int width;private int height;private int scaleWidth;double support = (double) 3.0;double PI = (double) 3.14159265358978;double[] contrib;double[] normContrib;double[] tmpContrib;int startContrib, stopContrib;int nDots;int nHalfDots;/*** Start: Use Lanczos filter to replace the original algorithm for image* scaling. Lanczos improves quality of the scaled image modify by :blade*/public BufferedImage imageZoomOut(BufferedImage srcBufferImage, int w, int h) {width = srcBufferImage.getWidth();height = srcBufferImage.getHeight();scaleWidth = w;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;// update by libradouble wt = w > width ? width : w;double ht = h > height ? height : h;scaleH = (double) wt / (double) width;scaleV = (double) ht / (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 * PI) / (x * PI) * Math.sin(x * PI / Support)/ (x * 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];// System.out.println(valueRed+"->"+Clip((int)valueRed)+"<-");//// System.out.println(valueGreen+"->"+Clip((int)valueGreen)+"<-");// System.out.println(valueBlue+"->"+Clip((int)valueBlue)+"<-"+"-->");}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;}/*** End: Use Lanczos filter to replace the original algorithm for image* scaling. Lanczos improves quality of the scaled image modify by :blade*/public boolean scale(String source, String target, int width, int height) {File f = new File(source);try {BufferedImage bi = ImageIO.read(f);BufferedImage out = null;ImageScale scal = new ImageScale();int _width = bi.getWidth();// addint _height = bi.getHeight();// addint[] _arr = this.getImageWidthAndHeight(_width, _height, width,height);// add// out = scal.imageZoomOut(bi, width, height);out = scal.imageZoomOut(bi, _arr[0], _arr[1]);File t = new File(target);ImageIO.write(out, "jpg", t);return true;} catch (IOException e) {e.printStackTrace();return false;}}/*** 得到放大或者缩小后的比例** @param W* 图片原宽* @param H* 原高* @param tarW* 转换后的宽* @param zoom* 放大还是缩小* @return 返回宽和高的数组*/private static int[] getImageWidthAndHeight(int orgW, int orgH, int avW,int avH) {int width = 0;int height = 0;if (orgW > 0 && orgH > 0) {if (orgW / orgH >= avW / avH) {if (orgW > avW) {width = avW;height = (orgH * avW) / orgW;} else {width = orgW;height = orgH;}System.out.println("++Widht:" + width + " Height" + height);} else {if (orgH > avH) {height = avH;width = (orgW * avH) / orgH;} else {width = orgW;height = orgH;}System.out.println("++Widht:" + width + " Height" + height);}}int[] arr = new int[2];arr[0] = width;arr[1] = height;// long start = System.currentTimeMillis();// int width = 0;// int height = 0;// if ((W / tarW) >= (H / tarH)) {// 宽的缩小比例大于高的// width = tarW;// height = H * tarW / W;// System.out.println(width + " " + height);// } else {// height = tarH;// width = W * tarH / H;// System.out.println(width + " " + height);// }// int[] arr = new int[2];// arr[0] = width;// arr[1] = height;// long end = System.currentTimeMillis();// System.out.println("宽高处理：" + (end - start));return arr;}public void picscale(String source, String target, int w, int h) {File f = new File(source);int width = 0;int height = 0;try {BufferedImage bi = ImageIO.read(f);int[] arr = getImageWidthAndHeight(bi.getWidth(), bi.getHeight(),w, h);width = arr[0];height = arr[1];BufferedImage out = null;ImageScale scal = new ImageScale();out = scal.imageZoomOut(bi, width, height);File t = new File(target);ImageIO.write(out, "jpg", t);} catch (IOException e) {e.printStackTrace();}}/****调用scale(源文件路径，保存路径，最大宽，最大高)***/public static void main(String[] args) {ImageScale is = new ImageScale();long start = System.currentTimeMillis();is.scale("D:/nie.jpg", "D:/t6.jpg", 250, 194);long end = System.currentTimeMillis();System.out.println("时间：" + (end - start));}}

PS：这里再为大家推荐几款比较实用的图片处理工具供大家参考使用：

在线图片转换BASE64工具：
http://tools.jb51.net/transcoding/img2base64

ICO图标在线生成工具：
http://tools.jb51.net/aideddesign/ico_img

在线Email邮箱图标制作工具：
http://tools.jb51.net/email/emaillogo

在线图片格式转换(jpg/bmp/gif/png)工具：
http://tools.jb51.net/aideddesign/picext

更多java相关内容感兴趣的读者可查看本站专题：《Java图片操作技巧汇总》、《java日期与时间操作技巧汇总》、《Java操作DOM节点技巧总结》、《Java文件与目录操作技巧汇总》及《Java数据结构与算法教程》。

希望本文所述对大家java程序设计有所帮助。