最近的業(yè)務(wù)里有一個(gè)場(chǎng)景：需要通過(guò)接口傳遞圖片的base64字符串實(shí)現(xiàn)圖片的上傳功能，但眾所周知，即使是post請(qǐng)求，也對(duì)報(bào)文的大小有所限制，而圖片的base64字符串有多長(zhǎng)呢，如果不是很清楚的話，可以打印出來(lái)看一下。
因此，需要將圖片進(jìn)行壓縮，使大小控制在可行的范圍內(nèi)，再轉(zhuǎn)成base64字符串，通過(guò)接口進(jìn)行傳輸。
具體實(shí)現(xiàn)代碼如下：

@Slf4j
public class ImageUtilJnb {
    private static int mb = 1048576;// 1MB

    public static void main(String[] args) {
        String fullPath="D:\\123.jpg";
        String newPath="D:\\321322198511205873F.jpg";

        long length = new File(fullPath).length();
        if (length / 1048576 >= JnbConstants.JNB_IMAGE_RATE) {// 如果圖片大于等于0.5MB 則按80%縮小
            try {
                ImageUtilJnb.zoom(fullPath, newPath, length, JnbConstants.JNB_IMAGE_RATE);
            } catch (IOException e) {
                log.error("出錯(cuò)啦:" + e);
            }
        }

        String base64Str = Base64Util.getBase64Str(newPath);
        System.out.println("base64Str===" + base64Str);

    }

    // 縮圖
    public static void zoom(String oldFile, String zoomFile,long length,double newRate) throws IOException {
        DecimalFormat df = new DecimalFormat("0.00");// 設(shè)置保留位數(shù)
        double rate=0.8;
        log.info("原始圖片大?。? + df.format((float) length / mb) + "MB");
        long newfile = new File(oldFile).length();
        int i = 1;
        // 如果首次壓縮還大于2MB則繼續(xù)處理
        while ((float) newfile / mb >= newRate) {
            log.info("壓縮后圖片大小：" + newfile);
            rate = rate - 0.05;// 暫定按照0.03頻率壓縮
            log.info(i + " rate=" + rate);
            BufferedImage srcImage = ImageIO.read(new File(oldFile));
            int WIDTH = (int) (srcImage.getWidth() * rate);
            int HEIGHT = (int) (srcImage.getHeight() * rate);
            BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
            Graphics g = image.getGraphics();
            g.drawImage(srcImage, 0, 0, WIDTH, HEIGHT, null);
            // 縮小
            ImageIO.write(image, "jpg", new File(zoomFile));
            i++;
            newfile = new File(zoomFile).length();
            log.info("壓縮次數(shù)：" + i);
        }
        // 調(diào)整方向
         BufferedImage newImage = ImageIO.read(new File(zoomFile));
         BufferedImage image1 = Rotate(newImage, 90);// 順時(shí)針旋轉(zhuǎn)90度
         ImageIO.write(image1, "jpg", new File(zoomFile));
        log.info("處理后圖片路徑：" + zoomFile + ";縮小之后大?。?
                + df.format((float) new File(zoomFile).length() / mb) + "MB");
    }

    /**
     * 對(duì)圖片進(jìn)行旋轉(zhuǎn)
     *
     * @param src
     *            被旋轉(zhuǎn)圖片
     * @param angel
     *            旋轉(zhuǎn)角度
     * @return 旋轉(zhuǎn)后的圖片
     */
    public static BufferedImage Rotate(Image src, int angel) {
        int src_width = src.getWidth(null);
        int src_height = src.getHeight(null);
        // 計(jì)算旋轉(zhuǎn)后圖片的尺寸
        Rectangle rect_des = CalcRotatedSize(new Rectangle(new Dimension(src_width, src_height)), angel);
        BufferedImage res = null;
        res = new BufferedImage(rect_des.width, rect_des.height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = res.createGraphics();
        // 進(jìn)行轉(zhuǎn)換
        g2.translate((rect_des.width - src_width) / 2, (rect_des.height - src_height) / 2);
        g2.rotate(Math.toRadians(angel), src_width / 2, src_height / 2);

        g2.drawImage(src, null, null);
        return res;
    }

    /**
     * 計(jì)算旋轉(zhuǎn)后的圖片
     *
     * @param src
     *            被旋轉(zhuǎn)的圖片
     * @param angel
     *            旋轉(zhuǎn)角度
     * @return 旋轉(zhuǎn)后的圖片
     */
    public static Rectangle CalcRotatedSize(Rectangle src, int angel) {
        // 如果旋轉(zhuǎn)的角度大于90度做相應(yīng)的轉(zhuǎn)換
        if (angel >= 90) {
            if (angel / 90 % 2 == 1) {
                int temp = src.height;
                src.height = src.width;
                src.width = temp;
            }
            angel = angel % 90;
        }

        double r = Math.sqrt(src.height * src.height + src.width * src.width) / 2;
        double len = 2 * Math.sin(Math.toRadians(angel) / 2) * r;
        double angel_alpha = (Math.PI - Math.toRadians(angel)) / 2;
        double angel_dalta_width = Math.atan((double) src.height / src.width);
        double angel_dalta_height = Math.atan((double) src.width / src.height);

        int len_dalta_width = (int) (len * Math.cos(Math.PI - angel_alpha - angel_dalta_width));
        int len_dalta_height = (int) (len * Math.cos(Math.PI - angel_alpha - angel_dalta_height));
        int des_width = src.width + len_dalta_width * 2;
        int des_height = src.height + len_dalta_height * 2;
        return new Rectangle(new Dimension(des_width, des_height));
    }

}