java 压缩图片

由于网站需要对上传的图片进行宽度判断缩放和质量压缩，以提升整体加载速度，于是我在网上找处理方法，
网上大多数是谷歌图片处理组件Thumbnails的介绍。最开始我用Thumbnails尝试，但不知道什么原因，没有任何效果，也不报错。
由于时间的关系，就没再深入研究，另寻他路。后来找到了下面的方法，这个方法优点在于完全基于Java自带API，调用也非常简单，如果只是缩放和压缩，这个方法足够了。

/**
     * 缩放图片(压缩图片质量，改变图片尺寸)
     * 若原图宽度小于新宽度，则宽度不变！
     * @param newWidth 新的宽度
     * @param quality 图片质量参数 0.7f 相当于70%质量
     */
    public static void imageResize(File originalFile, File resizedFile,
                              int maxWidth,int maxHeight, float quality) throws IOException {

        if (quality > 1) {
            throw new IllegalArgumentException(
                    "图片质量需设置在0.1-1范围");
        }

        ImageIcon ii = new ImageIcon(originalFile.getCanonicalPath());
        Image i = ii.getImage();
        Image resizedImage = null;

        int iWidth = i.getWidth(null);
        int iHeight = i.getHeight(null);

        int newWidth = maxWidth;
        if(iWidth < maxWidth){
            newWidth = iWidth;
        }


        if (iWidth >= iHeight) {
            resizedImage = i.getScaledInstance(newWidth, (newWidth * iHeight)
                    / iWidth, Image.SCALE_SMOOTH);
        }



        int newHeight = maxHeight;
        if(iHeight < maxHeight){
            newHeight = iHeight;
        }

        if(resizedImage==null && iHeight >= iWidth){
            resizedImage = i.getScaledInstance((newHeight * iWidth) / iHeight,
                    newHeight, Image.SCALE_SMOOTH);
        }

        // This code ensures that all the pixels in the image are loaded.
        Image temp = new ImageIcon(resizedImage).getImage();

        // Create the buffered image.
        BufferedImage bufferedImage = new BufferedImage(temp.getWidth(null),
                temp.getHeight(null), BufferedImage.TYPE_INT_RGB);

        // Copy image to buffered image.
        Graphics g = bufferedImage.createGraphics();

        // Clear background and paint the image.
        g.setColor(Color.white);
        g.fillRect(0, 0, temp.getWidth(null), temp.getHeight(null));
        g.drawImage(temp, 0, 0, null);
        g.dispose();

        // Soften.
        float softenFactor = 0.05f;
        float[] softenArray = { 0, softenFactor, 0, softenFactor,
                1 - (softenFactor * 4), softenFactor, 0, softenFactor, 0 };
        Kernel kernel = new Kernel(3, 3, softenArray);
        ConvolveOp cOp = new ConvolveOp(kernel, ConvolveOp.EDGE_NO_OP, null);
        bufferedImage = cOp.filter(bufferedImage, null);

        // Write the jpeg to a file.
        FileOutputStream out = new FileOutputStream(resizedFile);

        // Encodes image as a JPEG data stream
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);

        JPEGEncodeParam param = encoder
                .getDefaultJPEGEncodeParam(bufferedImage);

        param.setQuality(quality, true);

        encoder.setJPEGEncodeParam(param);
        encoder.encode(bufferedImage);
    } // Example usage

原贴：https://www.cnblogs.com/jsper/p/7652896.html