方法1：[第一种方法比后一种生成的缩略图要清晰]
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.WritableRaster;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.io.InputStream;
import java.io.File;
import java.io.FileOutputStream;
public class Test {
public static BufferedImage resize(BufferedImage source, int targetW, int targetH) {
// targetW，targetH分别表示目标长和宽
int type = source.getType();
BufferedImage target = null;
double sx = (double) targetW / source.getWidth();
double sy = (double) targetH / source.getHeight();
//这里想实现在targetW，targetH范围内实现等比缩放。如果不需要等比缩放
//则将下面的if else语句注释即可
if(sx>sy)
{
sx = sy;
targetW = (int)(sx * source.getWidth());
}else{
sy = sx;
targetH = (int)(sy * source.getHeight());
}
if (type == BufferedImage.TYPE_CUSTOM) { //handmade
ColorModel cm = source.getColorModel();
WritableRaster raster = cm.createCompatibleWritableRaster(targetW, targetH);
boolean alphaPremultiplied = cm.isAlphaPremultiplied();
target = new BufferedImage(cm, raster, alphaPremultiplied, null);
} else
target = new BufferedImage(targetW, targetH, type);
Graphics2D g = target.createGraphics();
//smoother than exlax:
g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY );
g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));
g.dispose();
return target;
}
public static void saveImageAsJpg (String fromFileStr,String saveToFileStr,int width,int hight)
throws Exception {
BufferedImage srcImage;
// String ex = fromFileStr.substring(fromFileStr.indexOf("."),fromFileStr.length());
String imgType = "JPEG";
if (fromFileStr.toLowerCase().endsWith(".png")) {
imgType = "PNG";
}
// System.out.println(ex);
File saveFile=new File(saveToFileStr);
File fromFile=new File(fromFileStr);
srcImage = ImageIO.read(fromFile);
if(width > 0 || hight > 0)
{
srcImage = resize(srcImage, width, hight);
}
ImageIO.write(srcImage, imgType, saveFile);
}
public static void main (String argv[]) {
try{
//参数1(from),参数2(to),参数3(宽),参数4(高)
Test.saveImageAsJpg("E:/Document/My Pictures/3.gif","c:/6.gif",50,50);
} catch(Exception e)
{
e.printStackTrace();
}
}
}
方法2：
import java.io.*;
import java.util.*;
import com.sun.image.codec.jpeg.*;
import java.awt.image.*;
import java.awt.*;
import java.net.*;
import java.applet.*;
import java.sql.*;
//缩略图类，
//本java类能将jpg图片文件，进行等比或非等比的大小转换。
//具体使用方法
//s_pic(大图片路径,生成小图片路径,大图片文件名,生成小图片文名,生成小图片宽度,生成小图片高度,是否等比缩放(默认为true))
public class Tes {
String InputDir; //输入图路径
String OutputDir; //输出图路径
String InputFileName; //输入图文件名
String OutputFileName; //输出图文件名
int OutputWidth = 80; //默认输出图片宽
int OutputHeight = 80; //默认输出图片高
int rate = 0;
boolean proportion = true; //是否等比缩放标记(默认为等比缩放)
public Tes() {
//初始化变量
InputDir = "";
OutputDir = "";
InputFileName = "";
OutputFileName = "";
OutputWidth = 80;
OutputHeight = 80;
rate = 0;
}
public void setInputDir(String InputDir) {
this.InputDir = InputDir;
}
public void setOutputDir(String OutputDir) {
this.OutputDir = OutputDir;
}
public void setInputFileName(String InputFileName) {
this.InputFileName = InputFileName;
}
public void setOutputFileName(String OutputFileName) {
this.OutputFileName = OutputFileName;
}
public void setOutputWidth(int OutputWidth) {
this.OutputWidth = OutputWidth;
}
public void setOutputHeight(int OutputHeight) {
this.OutputHeight = OutputHeight;
}
public void setW_H(int width, int height) {
this.OutputWidth = width;
this.OutputHeight = height;
}
public String s_pic() {
BufferedImage image;
String NewFileName;
//建立输出文件对象
File file = new File(OutputDir + OutputFileName);
FileOutputStream tempout = null;
try {
tempout = new FileOutputStream(file);
} catch (Exception ex) {
System.out.println(ex.toString());
}
Image img = null;
Toolkit tk = Toolkit.getDefaultToolkit();
Applet app = new Applet();
MediaTracker mt = new MediaTracker(app);
try {
img = tk.getImage(InputDir + InputFileName);
mt.addImage(img, 0);
mt.waitForID(0);
} catch (Exception e) {
e.printStackTrace();
}
if (img.getWidth(null) == -1) {
System.out.println(" can't read,retry!" + "
");
return "no";
} else {
int new_w;
int new_h;
if (this.proportion == true) { //判断是否是等比缩放.
//为等比缩放计算输出的图片宽度及高度
double rate1 = ((double) img.getWidth(null)) /
(double) OutputWidth + 0.1;
double rate2 = ((double) img.getHeight(null)) /
(double) OutputHeight + 0.1;
double rate = rate1 > rate2 ? rate1 : rate2;
new_w = (int) (((double) img.getWidth(null)) / rate);
new_h = (int) (((double) img.getHeight(null)) / rate);
} else {
new_w = OutputWidth; //输出的图片宽度
new_h = OutputHeight; //输出的图片高度
}
BufferedImage buffImg = new BufferedImage(new_w, new_h,
BufferedImage.TYPE_INT_RGB);
Graphics g = buffImg.createGraphics();
g.setColor(Color.white);
g.fillRect(0, 0, new_w, new_h);
g.drawImage(img, 0, 0, new_w, new_h, null);
g.dispose();
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(tempout);
try {
encoder.encode(buffImg);
tempout.close();
} catch (IOException ex) {
System.out.println(ex.toString());
}
}
return "ok";
}
public String s_pic(String InputDir, String OutputDir, String InputFileName,
String OutputFileName) {
//输入图路径
this.InputDir = InputDir;
//输出图路径
this.OutputDir = OutputDir;
//输入图文件名
this.InputFileName = InputFileName;
//输出图文件名
this.OutputFileName = OutputFileName;
return s_pic();
}
public String s_pic(String InputDir, String OutputDir, String InputFileName,
String OutputFileName, int width, int height,
boolean gp) {
//输入图路径
this.InputDir = InputDir;
//输出图路径
this.OutputDir = OutputDir;
//输入图文件名
this.InputFileName = InputFileName;
//输出图文件名
this.OutputFileName = OutputFileName;
//设置图片长宽
setW_H(width, height);
//是否是等比缩放 标记
this.proportion = gp;
return s_pic();
}
public static void main(String[] a) {
//s_pic(大图片路径,生成小图片路径,大图片文件名,生成小图片文名,生成小图片宽度,生成小图片高度)
Tes mypic = new Tes();
System.out.println(
mypic.s_pic("E:\\Document\\My Pictures\\",
"E:\\Document\\My Pictures\\",
"topbg-3.gif", "3.gif", 400, 400, true)
);
}
}
3.jsp方式
java.io.*,java.awt.Image,java.awt.image.*,com.sun.image.codec.jpeg.*,
try
{
java.io.File file = new java.io.File("E:\\Document\\My Pictures\\3.gif");
String newurl="E:\\Document\\My Pictures\\32.gif"; //新的缩略图保存地址
Image src = javax.imageio.ImageIO.read(file); //构造Image对象
float tagsize=200;
int old_w=src.getWidth(null); //得到源图宽
int old_h=src.getHeight(null);
int new_w=0;
int new_h=0; //得到源图长
int tempsize;
float tempdouble;
if(old_w>old_h){
tempdouble=old_w/tagsize;
}else{
tempdouble=old_h/tagsize;
}
new_w=Math.round(old_w/tempdouble);
new_h=Math.round(old_h/tempdouble);//计算新图长宽
BufferedImage tag = new BufferedImage(new_w,new_h,BufferedImage.TYPE_INT_RGB);
tag.getGraphics().drawImage(src,0,0,new_w,new_h,null); //绘制缩小后的图
FileOutputStream newimage=new FileOutputStream(newurl); //输出到文件流
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(newimage);
encoder.encode(tag); //近JPEG编码
newimage.close();
}catch (Exception e){
e.toString();
}
