本文实例为大家分享了Java实现自动生成缩略图片的具体代码，供大家参考，具体内容如下
一、自动生成缩略图方法：
package writeimg;
import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
public class JpegTool {
private boolean isInitFlag = false; // 对象是否己经初始化
private String pic_big_pathfilename = null; //定义源图片所在的带路径目录的文件名
private String pic_small_pathfilename = null; // 生成小图片的带存放路径目录的文件名
private int smallpicwidth = 0; //定义生成小图片的宽度和高度，给其一个就可以了
private int smallpicheight = 0;
private int pic_big_width=0;
private int pic_big_height=0;
private double picscale = 0; //定义小图片的相比原图片的比例
public JpegTool(){
this.isInitFlag = false;
}
private void resetJpegToolParams(){
this.picscale = 0;
this.smallpicwidth = 0;
this.smallpicheight = 0;
this.isInitFlag = false;
}
public void SetScale(double scale) throws JpegToolException
{
if(scale<=0){
throw new JpegToolException(" 缩放比例不能为 0 和负数！ ");
}
this.resetJpegToolParams();
this.picscale = scale;
this.isInitFlag = true;
}
public void SetSmallWidth(int smallpicwidth) throws JpegToolException
{
if(smallpicwidth<=0)
{
throw new JpegToolException(" 缩影图片的宽度不能为 0 和负数！ ");
}
this.resetJpegToolParams();
this.smallpicwidth = smallpicwidth;
this.isInitFlag = true;
}
public void SetSmallHeight(int smallpicheight) throws JpegToolException {
if(smallpicheight<=0)
{
throw new JpegToolException(" 缩影图片的高度不能为 0 和负数！ ");
}
this.resetJpegToolParams();
this.smallpicheight = smallpicheight;
this.isInitFlag = true;
}
public String getpic_big_pathfilename()
{
return this.pic_big_pathfilename;
}
public String getpic_small_pathfilename()
{
return this.pic_small_pathfilename;
}
public int getsrcw()
{
return this.pic_big_width;
}
public int getsrch()
{
return this.pic_big_height;
}
public void doFinal(String pic_big_pathfilename,String pic_small_pathfilename) throws JpegToolException {
if(!this.isInitFlag){
throw new JpegToolException(" 对象参数没有初始化！ ");
}
if(pic_big_pathfilename==null || pic_small_pathfilename==null){
throw new JpegToolException(" 包含文件名的路径为空！ ");
}
if((!pic_big_pathfilename.toLowerCase().endsWith("jpg")) && (!pic_big_pathfilename.toLowerCase().endsWith("jpeg"))){
throw new JpegToolException(" 只能处理 JPG/JPEG 文件！ ");
}
if((!pic_small_pathfilename.toLowerCase().endsWith("jpg")) && !pic_small_pathfilename.toLowerCase().endsWith("jpeg")){
throw new JpegToolException(" 只能处理 JPG/JPEG 文件！ ");
}
this.pic_big_pathfilename=pic_big_pathfilename;
this.pic_small_pathfilename=pic_small_pathfilename;
int smallw = 0;
int smallh = 0;
// 新建源图片和生成的小图片的文件对象
File fi = new File(pic_big_pathfilename);
File fo = new File(pic_small_pathfilename);
//生成图像变换对象
AffineTransform transform = new AffineTransform();
//通过缓冲读入源图片文件
BufferedImage bsrc = null;
try {
bsrc = ImageIO.read(fi);
}catch (IOException ex) {
throw new JpegToolException(" 读取源图像文件出错！ ");
}
this.pic_big_width= bsrc.getWidth();// 原图像的长度
this.pic_big_height = bsrc.getHeight();// 原图像的宽度
double scale = (double)pic_big_width/pic_big_height;// 图像的长宽比例
if(this.smallpicwidth!=0)
{// 根据设定的宽度求出长度
smallw = this.smallpicwidth;// 新生成的缩略图像的长度
smallh = (smallw*pic_big_height)/pic_big_width ;// 新生成的缩略图像的宽度
}
else if(this.smallpicheight!=0)
{// 根据设定的长度求出宽度
smallh = this.smallpicheight;// 新生成的缩略图像的长度
smallw = (smallh*pic_big_width)/pic_big_height;// 新生成的缩略图像的宽度
}
else if(this.picscale!=0)
{// 根据设置的缩小比例设置图像的长和宽
smallw = (int)((float)pic_big_width*this.picscale);
smallh = (int)((float)pic_big_height*this.picscale);
}
else
{
throw new JpegToolException(" 对象参数初始化不正确！ ");
}
double sx = (double)smallw/pic_big_width;//小/大图像的宽度比例
double sy = (double)smallh/pic_big_height;//小/大图像的高度比例
transform.setToScale(sx,sy);// 设置图像转换的比例
//生成图像转换操作对象
AffineTransformOp ato = new AffineTransformOp(transform,null);
//生成缩小图像的缓冲对象
BufferedImage bsmall = new BufferedImage(smallw,smallh,BufferedImage.TYPE_3BYTE_BGR);
//生成小图像
ato.filter(bsrc,bsmall);
//输出小图像
try{
ImageIO.write(bsmall, "jpeg", fo);
}
catch (IOException ex1)
{
throw new JpegToolException(" 写入缩略图像文件出错！ ");
}
}
}二、异常处理类：
package jpegtool;
public class JpegToolException extends Exception {
private String errMsg = "";
public JpegToolException(String errMsg)
{
this.errMsg = errMsg;
}
public String getMsg(){
return "JpegToolException:"+this.errMsg;
}
}三、调用的例子：
package writeimg;
public class T {
public static void main(String[] args) {
JpegTool j = new JpegTool();
try {
j.SetScale(0.7);
j.SetSmallHeight(100);
j.doFinal("D:\\305\\c\\javatest\\src\\11.jpg","D:\\305\\c\\javatest\\src\\22.jpg");
} catch (JpegToolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持编程网。
