Java图片Base64格式压缩大小至40k之内

Maven中用到的依赖：

        <dependency>
            <groupId>net.coobird</groupId>
            <artifactId>thumbnailator</artifactId>
            <version>0.4.8</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.30</version>
        </dependency>

base64转换成BufferedImage:

public static BufferedImage base64String2BufferedImage(String base64string) {
        BufferedImage image = null;
        try {
            InputStream stream = BaseToInputStream(base64string);
            image = ImageIO.read(stream);
        } catch (IOException e) {
            LOG.info("");
        }
        return image;
}

BufferedImage转换成base64，在这里需要设置图片格式，如下是jpg格式图片：

public static String imageToBase64(BufferedImage bufferedImage) {
        Base64 encoder = new Base64();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            ImageIO.write(bufferedImage, "jpg", baos);
        } catch (IOException e) {
            LOG.info("");
        }
        return new String(encoder.encode((baos.toByteArray())));
}

Base64转换成InputStream:

  private static InputStream BaseToInputStream(String base64string){
        ByteArrayInputStream stream = null;
        try {
            BASE64Decoder decoder = new BASE64Decoder();
            byte[] bytes1 = decoder.decodeBuffer(base64string);
            stream = new ByteArrayInputStream(bytes1);
        } catch (Exception e) {
            // TODO: handle exception
        }
        return stream;
    }

压缩图片至40k之内，将原图片的长宽分别压缩为原图片的1/3，如果图片大小大于40k，则继续进行压缩。

public static String resizeImageTo40K(String base64Img) {
        try {
            BufferedImage src = base64String2BufferedImage(base64Img);
            BufferedImage output = Thumbnails.of(src).size(src.getWidth()/3, src.getHeight()/3).asBufferedImage();
            String base64 = imageToBase64(output);
            if (base64.length() - base64.length() / 8 * 2 > 40000) {
                output = Thumbnails.of(output).scale(1/(base64.length()/40000)).asBufferedImage();
                base64 = imageToBase64(output);
            }
            return base64;
        } catch (Exception e) {
            return base64Img;
        }
    }

图片的Base64大小计算为：

base64.length() - base64.length() / 8 * 2 

图片压缩的验证方法：

public static void main(String[] args){
         String base64="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