java按比例压缩图片的源代码,用java如何把图片处理到指定大小

用java如何把图片处理到指定大小

前言:

朋友在做图片切割的时候遇到一个问题：如何用java如何把图片处理到指定大小？
切割程序如下：
public void cut(String srcImageFile,FileOutputStream fileout, int w, int h, int x1,
int y1, int sw, int sh) {
// TODO Auto-generated method stub
try {

// http://localhost:8080/ImpCra/createServlet?p=Sunset.jpg&x=117&y=201&w=61&h=50&pw=300&ph=400

Image img;

ImageFilter cropFilter;
// 读取源图像
BufferedImage bi = ImageIO.read(new File(srcImageFile));

if (sw >= w && sh >= h) {

Image image = bi.getScaledInstance(sw, sh, Image.SCALE_DEFAULT);

// 剪切起始坐标点
int x = x1;
int y = y1;

int destWidth = w; // 切片宽度
int destHeight = h; // 切片高度

// 图片比例
double pw = sw;
double ph = sh;

double m = (double) sw / pw;
double n = (double) sh / ph;
System.out.println(m);
int wth = (int) (destWidth * m);
int hth = (int) (destHeight * n);
int xx = (int) (x * m);
int yy = (int) (y * n);

// 四个参数分别为图像起点坐标和宽高
// 即: CropImageFilter(int x,int y,int width,int height)

cropFilter = new CropImageFilter(xx, yy, wth, hth);
img = Toolkit.getDefaultToolkit().createImage(
new FilteredImageSource(image.getSource(), cropFilter));

BufferedImage tag = new BufferedImage(w, h,
BufferedImage.TYPE_INT_RGB);
Graphics g = tag.getGraphics();
g.drawImage(img, 0, 0, null); // 绘制缩小后的图
g.dispose();

// 输出为文件
ImageIO.write(tag, "JPEG", fileout);

}

} catch (Exception e) {
e.printStackTrace();
}
}

进入正题:
解决方案参考源码，java按比例压缩图片的源代码如下：

public static void uploadImage(File p_in,File p_out,int height,int width,String ftype) throws FileNotFoundException,IOException
{
// 取得图片处理
// ConvertImageFactory l_factory = ConvertImageFactory.getInstance();
// AbstractProduct l_product = l_factory.createAbstractProduct(p_SourceFile.getContentType());
// boolean l_result = l_product.convertImageSize(p_SourceFile
// .getInputStream(), p_path );
InputStream l_in = new FileInputStream(p_in);
OutputStream l_out = new FileOutputStream(p_out);
chgPic(l_in,l_out,width,height,ftype);


}

//按比例压缩图片
public static boolean chgPic(InputStream in, OutputStream out,int newWidth, int newHeight,String ftype) {
BufferedImage img = null;
FileInputStream newin=null;
File tempfile=null;
try {
if(ftype.compareToIgnoreCase("bmp")==0){
PNGDecodeParam decodeParam = new PNGDecodeParam();
String l_tempfile = Tool.createNewFileName("jpg");

tempfile = new File(l_tempfile);
JPEGEncodeParam encodeParam = new JPEGEncodeParam();
//根据路径打开输出流
FileOutputStream tempout;
tempout = new FileOutputStream(tempfile);
ImageDecoder decoder = ImageCodec.createImageDecoder("BMP",in,decodeParam);
RenderedImage image = decoder.decodeAsRenderedImage();
ImageEncoder encoder = ImageCodec.createImageEncoder("JPEG",tempout,encodeParam);
encoder.encode(image);
tempout.close();

newin = new FileInputStream(tempfile);
img = ImageIO.read(newin);
}else{
img = ImageIO.read(in);
}

int width = img.getWidth(null);
int height = img.getHeight(null);

if (newWidth >= width) {
if (newHeight < height) {
width = (int) (width * newHeight / height);
height = newHeight;
}
} else {
if (newHeight >= height) {
height = (int) (height * newWidth / width);
width = newWidth;
} else {
if (height > width) {
width = (int) (width * newHeight / height);
height = newHeight;
} else {
height = (int) (height * newWidth / width);
width = newWidth;
}
}
}

BufferedImage img2 = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
img2.getGraphics().drawImage(img, 0, 0, width, height, null);

if (ftype.compareToIgnoreCase("jpg") == 0 || ftype.compareToIgnoreCase("jpeg") == 0 ) {
ImageIO.write(img2, "jpg", out);
} else
ImageIO.write(img2, "png", out);

if( ftype.compareToIgnoreCase("bmp") == 0){
ImageIO.write(img2, "jpg", out);
newin.close();
tempfile.delete();
}
return true;
} catch (Exception ex) {
ex.printStackTrace();
return false;
}finally{
try{
in.close();
out.close();
} catch (IOException e) {

}
}
}