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();
}
}
