上传一张高清图，生成两张不同大小的缩略图，缩略图变的很模糊。png的图片变成黑色背景了。代码如下
public void changImg(String path){
try{
Filej_file=new java.io.File(getHTTP.getServletContext().getRealPath("")+"/upfiles/newsImg/goods");
if(!j_file.exists()){
j_file.mkdirs();
}
//----上传完成，开始生成缩略图---goods
java.io.File goods_file = new java.io.File(getHTTP.getServletContext().getRealPath("")+"/"+path);//读入刚才上传的文件
String newpath=path.substring(0, path.lastIndexOf("/"));
String fileName=path.substring(path.lastIndexOf("/")+1, path.length());
String newgoods_url=getHTTP.getServletContext().getRealPath("")+"/"+newpath+"/goods/"+fileName;//新的缩略图保存地址
Image src=javax.imageio.ImageIO.read(goods_file);
float tagsize=400;
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(newgoods_url); //输出到文件流
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(newimage);
encoder.encode(tag); //近JPEG编码
newimage.close();
//----上传完成，开始生成缩略图---thumb
java.io.File thumb_file = new java.io.File(getHTTP.getServletContext().getRealPath("")+"/"+path);//读入刚才上传的文件
String newthumb_url=getHTTP.getServletContext().getRealPath("")+"/"+newpath+"/thumb/"+fileName;//新的缩略图保存地址
j_file=new java.io.File(getHTTP.getServletContext().getRealPath("")+"/upfiles/newsImg/thumb");
if(!j_file.exists()){
j_file.mkdirs();
}
Image thumb_src = javax.imageio.ImageIO.read(thumb_file);//构造Image对象
float thumb_tagsize=80;
int thumb_old_w=thumb_src.getWidth(null);//得到源图宽
int thumb_old_h=thumb_src.getHeight(null);
int thumb_new_w=0;
int thumb_new_h=0;//得到源图长
int thumb_tempsize;
float thumb_tempdouble;
if(thumb_old_w>thumb_old_h){
thumb_tempdouble=thumb_old_w/thumb_tagsize;
}else{
thumb_tempdouble=thumb_old_h/thumb_tagsize;
}
thumb_new_w=Math.round((thumb_old_w/thumb_tempdouble));
thumb_new_h=Math.round(thumb_old_h/thumb_tempdouble);//计算新图长宽
BufferedImage thumb_tag = new BufferedImage(thumb_new_w,thumb_new_h,BufferedImage.TYPE_INT_RGB);
thumb_tag.getGraphics().drawImage(thumb_src,0,0,thumb_new_w,thumb_new_h,null);//绘制缩小后的图
FileOutputStream thumb_newimage=new FileOutputStream(newthumb_url); //输出到文件流
JPEGImageEncoder thumb_encoder = JPEGCodec.createJPEGEncoder(thumb_newimage);
thumb_encoder.encode(thumb_tag); //近JPEG编码
thumb_newimage.close();
}catch(Exception e){
e.printStackTrace();
}
}
