public static void PngResize(String srcImageFile, String result, int width,int height) {try {BufferedImage src = ImageIO.read(new File(srcImageFile)); Image image = src.getScaledInstance(width,height,Image.SCALE_DEFAULT);BufferedImage newImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);Graphics g = newImage.createGraphics();g.drawImage(image, 0, 0, null);g.dispose();newImage.flush();ImageIO.write(newImage, "PNG", new File(result));  } catch (IOException e) {e.printStackTrace();}
}

public static int PngResize(String srcImageFile, String result, float width_, float height_){try {Thumbnails.of(srcImageFile).size((int)width_, (int)height_).outputQuality(1f).keepAspectRatio(false).toFile(result); } catch (IOException e) {// TODO Auto-generated catch block
        e.printStackTrace();}
}

//按指定大小把图片进行缩和放（会遵循原图高宽比例）  此处把图片压成400×500的缩略图  变为400*300,遵循原图比例缩或放到400*某个高度
Thumbnails.of(fromPic).size(400,500).toFile(toPic);////按照比例进行缩小和放大
Thumbnails.of(fromPic).scale(0.2f).toFile(toPic);//按比例缩小
Thumbnails.of(fromPic).scale(2f);//按比例放大//不按比例，就按指定的大小进行缩放
Thumbnails.of(fromPic).size(100, 100).keepAspectRatio(false).toFile(toPic);
//或者Thumbnails.of(fromPic).forceSize(100,100).toFile(toPic);
//旋转图片，rotate(角度),正数则为顺时针，负数则为逆时针
Thumbnails.of(fromPic).size(200,200).rotate(90).toFile(toPic);//图片尺寸不变，压缩图片文件大小outputQuality实现,参数1为最高质量
Thumbnails.of(fromPic).scale(1f).outputQuality(0.25f).toFile(toPic);//给图片加水印，watermark(位置，水印图，透明度)Positions.CENTER表示加在中间
Thumbnails.of(fromPic).size(400,400).watermark(Positions.CENTER,ImageIO.read(waterPic),0.5f).outputQuality(0.8f).toFile(toPic);//用sourceRegion()实现图片裁剪//图片中心300*300的区域,Positions.CENTER表示中心，还有许多其他位置可选
Thumbnails.of(fromPic).sourceRegion(Positions.CENTER,300,300).size(300,300).toFile(toPic);//图片中上区域300*300的区域
Thumbnails.of(fromPic).sourceRegion(Positions.TOP_CENTER,300,300).size(300,300).toFile(toPic);//用outputFormat(图像格式)转换图片格式，保持原尺寸不变
Thumbnails.of(fromPic).scale(1f).outputFormat("png").toFile("picture/png格式的图片.png");//输出成文件流OutputStream
OutputStream os=new FileOutputStream(toPic);
Thumbnails.of(fromPic).size(120,120).toOutputStream(os);//输出BufferedImage,asBufferedImage()返回BufferedImage
BufferedImage bi=Thumbnails.of(fromPic).size(120,120).asBufferedImage();
ImageIO.write(bi,"jpg",toPic);//压缩至指定图片尺寸（例如：横400高300），保持图片不变形，多余部分裁剪掉
BufferedImage image = ImageIO.read(fromPic);
Builder<BufferedImage> builder = null;int imageWidth = image.getWidth();
int imageHeitht = image.getHeight();
if ((float)300 / 400 != (float)imageWidth / imageHeitht) {if (imageWidth > imageHeitht) {image = Thumbnails.of(fromPic).height(300).asBufferedImage();} else {image = Thumbnails.of(fromPic).width(400).asBufferedImage();}builder = Thumbnails.of(image).sourceRegion(Positions.CENTER, 400, 300).size(400, 300);
} else {builder = Thumbnails.of(image).size(400, 300);
}
builder.outputFormat("jpg").toFile(toPic);