springmvc压缩图片并解决透明边框变黑色问题

1.springmvc接受MultipartFile通过流直接压缩

可以使用

MultipartFile自带的getInputStream获取流,做到了直接压缩流文件.

  /**
     * 等比例压缩算法：
     * 算法思想：根据压缩基数和压缩比来压缩原图，生产一张图片效果最接近原图的缩略图
     * @param comBase 压缩基数
     * @param scale 压缩限制(宽/高)比例  一般用1：
     * 当scale>=1,缩略图height=comBase,width按原图宽高比例;若scale<1,缩略图width=comBase,height按原图宽高比例
     * @throws Exception
     * @author hex
     */
    private String saveMinPhoto(InputStream inputStream, String filename, String relativePath, double comBase,
                                      double scale) throws Exception {
        BufferedImage src = ImageIO.read(inputStream);
        int srcHeight = src.getHeight(null);
        int srcWidth = src.getWidth(null);
        int deskHeight = 0;// 缩略图高
        int deskWidth = 0;// 缩略图宽
        double srcScale = (double) srcHeight / srcWidth;
        /**缩略图宽高算法*/
        if ((double) srcHeight > comBase || (double) srcWidth > comBase) {
            if (srcScale >= scale || 1 / srcScale > scale) {
                if (srcScale >= scale) {
                    deskHeight = (int) comBase;
                    deskWidth = srcWidth * deskHeight / srcHeight;
                } else {
                    deskWidth = (int) comBase;
                    deskHeight = srcHeight * deskWidth / srcWidth;
                }
            } else {
                if ((double) srcHeight > comBase) {
                    deskHeight = (int) comBase;
                    deskWidth = srcWidth * deskHeight / srcHeight;
                } else {
                    deskWidth = (int) comBase;
                    deskHeight = srcHeight * deskWidth / srcWidth;
                }
            }
        } else {
            deskHeight = srcHeight;
            deskWidth = srcWidth;
        }
        String fName = System.currentTimeMillis() + "_" + Math.random() * 1000;
        String fileNames = fName + filename.substring(filename.indexOf("."));
        String fullPath = uploadImgsOrder + relativePath;
        File uf = new File(fullPath);
        // 不存在则根据用户id创建文件
        if (!uf.exists()) {
            uf.mkdirs();
        }
        BufferedImage tag = new BufferedImage(deskWidth, deskHeight, BufferedImage.TYPE_INT_RGB);
        //解决压缩后图片透明变黑色问题
        Graphics2D g2d = tag.createGraphics();
        tag = g2d.getDeviceConfiguration().createCompatibleImage(deskWidth, deskHeight,
                Transparency.TRANSLUCENT);
        g2d.dispose();
        Image from = src.getScaledInstance(deskWidth, deskHeight, BufferedImage.SCALE_AREA_AVERAGING);
        //绘制缩小后的图
        tag.getGraphics().drawImage(from, 0, 0, deskWidth, deskHeight, null);
        //输出到文件流
        String formatName = filename.substring(filename.lastIndexOf(".") + 1);

        ImageIO.write(tag,formatName, new File(fullPath+fileNames));
        String bucket = getVisitPath() + relativePath + fileNames;
        return bucket;
    }

2.通过读取本地文件压缩

  /**
     * 等比例压缩算法：
     * 算法思想：根据压缩基数和压缩比来压缩原图，生产一张图片效果最接近原图的缩略图
     * @param srcURL 原图地址
     * @param deskURL 缩略图地址
     * @param comBase 压缩基数
     * @param scale 压缩限制(宽/高)比例  一般用1：
     * 当scale>=1,缩略图height=comBase,width按原图宽高比例;若scale<1,缩略图width=comBase,height按原图宽高比例
     * @throws Exception
     * @author hex
     */
    public static void saveMinPhoto(String srcURL, String deskURL, double comBase,
                                    double scale) throws Exception {
        File srcFile = new java.io.File(srcURL);
        Image src = ImageIO.read(srcFile);
        int srcHeight = src.getHeight(null);
        int srcWidth = src.getWidth(null);
        int deskHeight = 0;// 缩略图高
        int deskWidth = 0;// 缩略图宽
        double srcScale = (double) srcHeight / srcWidth;
        /**缩略图宽高算法*/
        if ((double) srcHeight > comBase || (double) srcWidth > comBase) {
            if (srcScale >= scale || 1 / srcScale > scale) {
                if (srcScale >= scale) {
                    deskHeight = (int) comBase;
                    deskWidth = srcWidth * deskHeight / srcHeight;
                } else {
                    deskWidth = (int) comBase;
                    deskHeight = srcHeight * deskWidth / srcWidth;
                }
            } else {
                if ((double) srcHeight > comBase) {
                    deskHeight = (int) comBase;
                    deskWidth = srcWidth * deskHeight / srcHeight;
                } else {
                    deskWidth = (int) comBase;
                    deskHeight = srcHeight * deskWidth / srcWidth;
                }
            }
        } else {
            deskHeight = srcHeight;
            deskWidth = srcWidth;
        }
        BufferedImage tag = new BufferedImage(deskWidth, deskHeight, BufferedImage.TYPE_3BYTE_BGR);
        tag.getGraphics().drawImage(src, 0, 0, deskWidth, deskHeight, null); //绘制缩小后的图
        String formatName = deskURL.substring(deskURL.lastIndexOf(".") + 1);
        ImageIO.write(tag,formatName, new File(deskURL));
    }

    public static void main(String args[]) throws Exception {
        saveMinPhoto("D://123.jpg", "D://1243.jpg", 800, 1);
    }