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：

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 libra
double 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();// 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]);
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：

ico图标在线生成工具：

在线email邮箱图标制作工具：

在线图片格式转换(jpg/bmp/gif/png)工具：

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。