java中的图片按比例缩放功能

1. 按固定长宽进行缩放

/*

* 图片缩放,w，h为缩放的目标宽度和高度

* src为源文件目录，dest为缩放后保存目录

*/

public static void zoomImage(String src,String dest,int w,int h) throws Exception {

double wr=0,hr=0;

File srcFile = new File(src);

File destFile = new File(dest);

BufferedImage bufImg = ImageIO.read(srcFile); //读取图片

Image Itemp = bufImg.getScaledInstance(w, h, bufImg.SCALE_SMOOTH);//设置缩放目标图片模板

wr=w*1.0/bufImg.getWidth(); //获取缩放比例

hr=h*1.0 / bufImg.getHeight();

AffineTransformOp ato = new AffineTransformOp(AffineTransform.getScaleInstance(wr, hr), null);

Itemp = ato.filter(bufImg, null);

try {

ImageIO.write((BufferedImage) Itemp,dest.substring(dest.lastIndexOf(".")+1), destFile); //写入缩减后的图片

} catch (Exception ex) {

ex.printStackTrace();

}

}

2. 按固定文件大小进行缩放

/*

* 图片按比率缩放

* size为文件大小

*/

public static void zoomImage(String src,String dest,Integer size) throws Exception {

File srcFile = new File(src);

File destFile = new File(dest);

long fileSize = srcFile.length();

if(fileSize < size * 1024) //文件大于size k时，才进行缩放,注意：size以K为单位

return;

Double rate = (size * 1024 * 0.5) / fileSize; // 获取长宽缩放比例

BufferedImage bufImg = ImageIO.read(srcFile);

Image Itemp = bufImg.getScaledInstance(bufImg.getWidth(), bufImg.getHeight(), bufImg.SCALE_SMOOTH);

AffineTransformOp ato = new AffineTransformOp(AffineTransform.getScaleInstance(rate, rate), null);

Itemp = ato.filter(bufImg, null);

try {

ImageIO.write((BufferedImage) Itemp,dest.substring(dest.lastIndexOf(".")+1), destFile);

} catch (Exception ex) {

ex.printStackTrace();

}

}