java图片压缩指定大小

‘壹’ java将图片按比例缩小

Image srcImg = ImageIO.read(new FileInputStream(fnSrc) );//取源图
int width = 600; //假设要缩小到600点像素
int height = srcImg.getHeight(null)*600/srcImg.getWidth(null);//按比例，将高度缩减

System.out.println("Width: "+srcImg.getWidth(null));// 这几行是调试用
System.out.println("Height: "+srcImg.getHeight(null));
System.out.println("Width2: "+width);
System.out.println("Height2: "+height);

Image smallImg =srcImg.getScaledInstance(width, height, Image.SCALE_SMOOTH);//缩小

‘贰’ 您好！请问用java怎么将截取png的图片中间一部分，以及如何压缩一个png图片

• getSubimage方法是进行图片裁剪。

举例：
public static void main(String[] args) {
try {
//从特定文件载入
BufferedImage bi = ImageIO.read(new File("c:\test.png"));
bi.getSubimage(0, 0, 10, 10);//前两个值是坐标位置X、Y，后两个是长和宽
} catch (IOException e) {
e.printStackTrace();
}
}

• 以下是进行的图片压缩，涉及到多个工具类。
  

/**
* 图片工具类
* 压缩图片大小
* @author Cyw
* @version 1.0
*/
public class ZIPImage {

private File file = null;

private String outPutFilePath;

private String inPutFilePath;

private String inPutFileName;

private boolean autoBuildFileName;

private String outPutFileName;

private int outPutFileWidth = 100; // 默认输出图片宽

private int outPutFileHeight = 100; // 默认输出图片高

private static boolean isScaleZoom = true; // 是否按比例缩放

public ZIPImage() {
outPutFilePath = "";
inPutFilePath = "";
inPutFileName = "";
autoBuildFileName = true;
outPutFileName = "";
}

/**
*
* @param ipfp
* 源文件夹路径
* @param ipfn
* 源文件名
* @param opfp
* 目标文件路径
* @param opfn
* 目标文件名
*/
public ZIPImage(String ipfp, String ipfn, String opfp, String opfn) {
outPutFilePath = opfp;
inPutFilePath = ipfp;
inPutFileName = ipfn;
autoBuildFileName = true;
outPutFileName = opfn;
}

/**
*
* @param ipfp
* 源文件夹路径
* @param ipfn
* 源文件名
* @param opfp
* 目标文件路径
* @param opfn
* 目标文件名
* @param aBFN
* 是否自动生成目标文件名
*/
public ZIPImage(String ipfp, String ipfn, String opfp, String opfn,
boolean aBFN) {
outPutFilePath = opfp;
inPutFilePath = ipfp;
inPutFileName = ipfn;
autoBuildFileName = aBFN;
outPutFileName = opfn;
}

public boolean isAutoBuildFileName() {
return autoBuildFileName;
}

public void setAutoBuildFileName(boolean autoBuildFileName) {
this.autoBuildFileName = autoBuildFileName;
}

public String getInPutFilePath() {
return inPutFilePath;
}

public void setInPutFilePath(String inPutFilePath) {
this.inPutFilePath = inPutFilePath;
}

public String getOutPutFileName() {
return outPutFileName;
}

public void setOutPutFileName(String outPutFileName) {
this.outPutFileName = outPutFileName;
}

public String getOutPutFilePath() {
return outPutFilePath;
}

public void setOutPutFilePath(String outPutFilePath) {
this.outPutFilePath = outPutFilePath;
}

public int getOutPutFileHeight() {
return outPutFileHeight;
}

public void setOutPutFileHeight(int outPutFileHeight) {
this.outPutFileHeight = outPutFileHeight;
}

public int getOutPutFileWidth() {
return outPutFileWidth;
}

public void setOutPutFileWidth(int outPutFileWidth) {
this.outPutFileWidth = outPutFileWidth;
}

public boolean isScaleZoom() {
return isScaleZoom;
}

public void setScaleZoom(boolean isScaleZoom) {
this.isScaleZoom = isScaleZoom;
}

public String getInPutFileName() {
return inPutFileName;
}

public void setInPutFileName(String inPutFileName) {
this.inPutFileName = inPutFileName;
}

/**
* 压缩图片大小
*
* @return boolean
*/
public boolean compressImage() {
boolean flag = false;

try {
if (inPutFilePath.trim().equals("")) {
throw new NullPointerException("源文件夹路径不存在。");
}
if (inPutFileName.trim().equals("")) {
throw new NullPointerException("图片文件路径不存在。");
}
if (outPutFilePath.trim().equals("")) {
throw new NullPointerException("目标文件夹路径地址为空。");
} else {
if (!ZIPImage.mddir(outPutFilePath)) {
throw new FileNotFoundException(outPutFilePath
+ " 文件夹创建失败！");
}
}

if (this.autoBuildFileName) { // 自动生成文件名
String tempFile[] = getFileNameAndExtName(inPutFileName);
outPutFileName = tempFile[0] + "_cyw." + tempFile[1];
compressPic();
} else {
if (outPutFileName.trim().equals("")) {
throw new NullPointerException("目标文件名为空。");
}
compressPic();
}

} catch (Exception e) {
flag = false;
e.printStackTrace();
return flag;
}

return flag;
}

// 图片处理
private void compressPic() throws Exception {
try {
// 获得源文件
file = new File(inPutFilePath + inPutFileName);
if (!file.exists()) {
throw new FileNotFoundException(inPutFilePath + inPutFileName
+ " 文件不存在！");
}
Image img = ImageIO.read(file);
// 判断图片格式是否正确
if (img.getWidth(null) == -1) {
throw new Exception("文件不可读！");
} else {
int newWidth;
int newHeight;
// 判断是否是等比缩放
if (ZIPImage.isScaleZoom == true) {
// 为等比缩放计算输出的图片宽度及高度
double rate1 = ((double) img.getWidth(null))
/ (double) outPutFileWidth + 0.1;
double rate2 = ((double) img.getHeight(null))
/ (double) outPutFileHeight + 0.1;

// 根据缩放比率大的进行缩放控制
double rate = rate1 > rate2 ? rate1 : rate2;

newWidth = (int) (((double) img.getWidth(null)) / rate);
newHeight = (int) (((double) img.getHeight(null)) / rate);

} else {
newWidth = outPutFileWidth; // 输出的图片宽度
newHeight = outPutFileHeight; // 输出的图片高度
}

BufferedImage tag = new BufferedImage((int) newWidth,
(int) newHeight, BufferedImage.TYPE_INT_RGB);

/*
* Image.SCALE_SMOOTH 的缩略算法 生成缩略图片的平滑度的 优先级比速度高 生成的图片质量比较好 但速度慢
*/
tag.getGraphics().drawImage(
img.getScaledInstance(newWidth, newHeight,
Image.SCALE_SMOOTH), 0, 0, null);

FileOutputStream out = new FileOutputStream(outPutFilePath
+ outPutFileName);

JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
encoder.encode(tag);
out.close();

}
} catch (IOException ex) {
ex.printStackTrace();
}
}

/**
* 创建文件夹目录
*
* @param filePath
* @return
* @throws Exception
*/
@SuppressWarnings("unused")
private static boolean mddir(String filePath) throws Exception {
boolean flag = false;
File f = new File(filePath);
if (!f.exists()) {
flag = f.mkdirs();
} else {
flag = true;
}
return flag;
}

/**
* 获得文件名和扩展名
*
* @param fullFileName
* @return
* @throws Exception
*/
private String[] getFileNameAndExtName(String fullFileName)
throws Exception {
String[] fileNames = new String[2];
if (fullFileName.indexOf(".") == -1) {
throw new Exception("源文件名不正确！");
} else {
fileNames[0] = fullFileName.substring(0, fullFileName
.lastIndexOf("."));
fileNames[1] = fullFileName
.substring(fullFileName.lastIndexOf(".") + 1);
}
return fileNames;
}

public Image getSourceImage() throws IOException{
//获得源文件
file = new File(inPutFilePath + inPutFileName);
if (!file.exists()) {
throw new FileNotFoundException(inPutFilePath + inPutFileName
+ " 文件不存在！");
}
Image img = ImageIO.read(file);
return img;
}

/*
* 获得图片大小
* @path ：图片路径
*/
public long getPicSize(String path) {
File file = new File(path);
return file.length();
}

}

//下面是测试程序

package com.sun.util.cyw;

import java.awt.Image;
import java.io.IOException;

public class ImageTest {
public static void main(String[] args) throws IOException {
ZIPImage zip=new ZIPImage("d:\","1.jpg","d:\test\","处理后的图片.jpg",false);
zip.setOutPutFileWidth(1000);
zip.setOutPutFileHeight(1000);

Image image=zip.getSourceImage();
long size=zip.getPicSize("d:\1.jpg");
System.out.println("处理前的图片大小 width:"+image.getWidth(null));
System.out.println("处理前的图片大小 height:"+image.getHeight(null));
System.out.println("处理前的图片容量:"+ size +" bit");

zip.compressImage();
}
}

‘叁’ Java上传pdf文件，只压缩大小，不改变成.zip/.rar文件

Java上传pdf文件，只压缩大小，不改变成.zip/.rar文件
可以，压缩只是一种算法，什么语言都可以，比如某种格式的文件中1001010(二进制)代表汉子的"中"字，那么压缩算法就是在编码不冲突的情况下可以改变编码长度，比如压缩之后中字变成1010，这样就节省空间了，这是我随便举的例子，具体的对应算法可以网上查

‘肆’ java上传图片 生成缩略图，如果上传的图片尺寸比较小就压缩处理

//将图按比例缩小。
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.(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)
saveImageAsJpg("C:\\Documents and Settings\\xugang\\桌面\\tmr-06.jpg",
"C:\\Documents and Settings\\xugang\\桌面\\2.jpg",
120,120);
} catch(Exception e){
e.printStackTrace();
}

}

‘伍’ 求一个Java无损压缩图片的示例，把原图片复制到指定目录，按原图比例改变尺寸，不影响图片质量。

图片压缩就是讲图片的内存变小 对象数坑定有印象 你将压缩率改小一点 调整一下压缩率 到自己满意为止

‘陆’ 问题:java 压缩图片 要求:只压缩像素 注意:要理解像素的概念,最好有个例子

看看这个是否对你有用

‘柒’ 我在用java进行图片压缩时，遇到130MB 的图片是报错 ， 像十几MB时不会出错，

Runtime.getRuntime().maxMemory()，查看一下jvm最大内存，若小了，可通过java参数来设置，如 java -Xmx1024m Test，将最大堆空间设为1024m