java生成缩略图的方法示例
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：
packagecom.util;
importjava.awt.image.BufferedImage;
importjava.io.File;
importjava.io.IOException;
importjavax.imageio.ImageIO;
/**
*生成压缩图
*
*/
publicclassImageScale{
privateintwidth;
privateintheight;
privateintscaleWidth;
doublesupport=(double)3.0;
doublePI=(double)3.14159265358978;
double[]contrib;
double[]normContrib;
double[]tmpContrib;
intstartContrib,stopContrib;
intnDots;
intnHalfDots;
/**
*Start:UseLanczosfiltertoreplacetheoriginalalgorithmforimage
*scaling.Lanczosimprovesqualityofthescaledimagemodifyby:blade
*/
publicBufferedImageimageZoomOut(BufferedImagesrcBufferImage,intw,inth){
width=srcBufferImage.getWidth();
height=srcBufferImage.getHeight();
scaleWidth=w;
if(DetermineResultSize(w,h)==1){
returnsrcBufferImage;
}
CalContrib();
BufferedImagepbOut=HorizontalFiltering(srcBufferImage,w);
BufferedImagepbFinalOut=VerticalFiltering(pbOut,h);
returnpbFinalOut;
}
/**
*决定图像尺寸
*/
privateintDetermineResultSize(intw,inth){
doublescaleH,scaleV;
//updatebylibra
doublewt=w>width?width:w;
doubleht=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){
return1;
}
return0;
}//endofDetermineResultSize()
privatedoubleLanczos(inti,intinWidth,intoutWidth,doubleSupport){
doublex;
x=(double)i*(double)outWidth/(double)inWidth;
returnMath.sin(x*PI)/(x*PI)*Math.sin(x*PI/Support)
/(x*PI/Support);
}//endofLanczos()
//
//Assumption:samehorizontalandverticalscalingfactor
//
privatevoidCalContrib(){
nHalfDots=(int)((double)width*support/(double)scaleWidth);
nDots=nHalfDots*2+1;
try{
contrib=newdouble[nDots];
normContrib=newdouble[nDots];
tmpContrib=newdouble[nDots];
}catch(Exceptione){
System.out.println("initcontrib,normContrib,tmpContrib"+e);
}
intcenter=nHalfDots;
contrib[center]=1.0;
doubleweight=0.0;
inti=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>16;
}
privateintGetGreenValue(intrgbValue){
inttemp=rgbValue&0x0000ff00;
returntemp>>8;
}
privateintGetBlueValue(intrgbValue){
returnrgbValue&0x000000ff;
}
privateintComRGB(intredValue,intgreenValue,intblueValue){
return(redValue<<16)+(greenValue<<8)+blueValue;
}
//行水平滤波
privateintHorizontalFilter(BufferedImagebufImg,intstartX,intstopX,
intstart,intstop,inty,double[]pContrib){
doublevalueRed=0.0;
doublevalueGreen=0.0;
doublevalueBlue=0.0;
intvalueRGB=0;
inti,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));
returnvalueRGB;
}//endofHorizontalFilter()
//图片水平滤波
privateBufferedImageHorizontalFiltering(BufferedImagebufImage,intiOutW){
intdwInW=bufImage.getWidth();
intdwInH=bufImage.getHeight();
intvalue=0;
BufferedImagepbOut=newBufferedImage(iOutW,dwInH,
BufferedImage.TYPE_INT_RGB);
for(intx=0;x(dwInW-1)){
stopX=dwInW-1;
stop=nHalfDots+(dwInW-1-X);
}else{
stop=nHalfDots*2;
}
if(start>0||stop"+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);
returnvalueRGB;
}//endofVerticalFilter()
privateBufferedImageVerticalFiltering(BufferedImagepbImage,intiOutH){
intiW=pbImage.getWidth();
intiH=pbImage.getHeight();
intvalue=0;
BufferedImagepbOut=newBufferedImage(iW,iOutH,
BufferedImage.TYPE_INT_RGB);
for(inty=0;y(int)(iH-1)){
stopY=iH-1;
stop=nHalfDots+(iH-1-Y);
}else{
stop=nHalfDots*2;
}
if(start>0||stop255)
return255;
returnx;
}
/**
*End:UseLanczosfiltertoreplacetheoriginalalgorithmforimage
*scaling.Lanczosimprovesqualityofthescaledimagemodifyby:blade
*/
publicbooleanscale(Stringsource,Stringtarget,intwidth,intheight){
Filef=newFile(source);
try{
BufferedImagebi=ImageIO.read(f);
BufferedImageout=null;
ImageScalescal=newImageScale();
int_width=bi.getWidth();//add
int_height=bi.getHeight();//add
int[]_arr=this.getImageWidthAndHeight(_width,_height,width,
height);//add
//out=scal.imageZoomOut(bi,width,height);
out=scal.imageZoomOut(bi,_arr[0],_arr[1]);
Filet=newFile(target);
ImageIO.write(out,"jpg",t);
returntrue;
}catch(IOExceptione){
e.printStackTrace();
returnfalse;
}
}
/**
*得到放大或者缩小后的比例
*
*@paramW
*图片原宽
*@paramH
*原高
*@paramtarW
*转换后的宽
*@paramzoom
*放大还是缩小
*@return返回宽和高的数组
*/
privatestaticint[]getImageWidthAndHeight(intorgW,intorgH,intavW,
intavH){
intwidth=0;
intheight=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=newint[2];
arr[0]=width;
arr[1]=height;
//longstart=System.currentTimeMillis();
//intwidth=0;
//intheight=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=newint[2];
//arr[0]=width;
//arr[1]=height;
//longend=System.currentTimeMillis();
//System.out.println("宽高处理："+(end-start));
returnarr;
}
publicvoidpicscale(Stringsource,Stringtarget,intw,inth){
Filef=newFile(source);
intwidth=0;
intheight=0;
try{
BufferedImagebi=ImageIO.read(f);
int[]arr=getImageWidthAndHeight(bi.getWidth(),bi.getHeight(),
w,h);
width=arr[0];
height=arr[1];
BufferedImageout=null;
ImageScalescal=newImageScale();
out=scal.imageZoomOut(bi,width,height);
Filet=newFile(target);
ImageIO.write(out,"jpg",t);
}catch(IOExceptione){
e.printStackTrace();
}
}
/**
*
*调用scale(源文件路径，保存路径，最大宽，最大高)
*
*
*/
publicstaticvoidmain(String[]args){
ImageScaleis=newImageScale();
longstart=System.currentTimeMillis();
is.scale("D:/nie.jpg","D:/t6.jpg",250,194);
longend=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。