某些图片需作下压缩处理，以便某些页面图片列表使用压缩图，从而提高页面图片的加载速度,图片压缩的时机可选在上传图片的时候（新增时）或者读取图片的时候。（对已有图片作压缩，历史数据）。访问图片的方法是在普通图片的前面加上尺寸前缀。如：http://xxx/image/100x100-compress-aaaaaaaaaaaaaaaaaaaaaaaaaaaa.jpg

图片压缩时机：

下面打开压缩图的办法是存在风险的，会导致图片无限增加。由于本项目是小圈子内的小群体使用。不存在该问题。如果要用，需要把catch里面的代码删除或者对可压缩的尺寸作下限制

public class ImageCompressionHelper {

    @Autowired
    private FileStoreService fileStoreService;
    @Autowired
    private FileInfoMapper fileInfoMapper;

    public final static String COMPRESS_SEPARATOR = "-compress-";

    public void compressionImage(String imgPxs, FileInfo fileInfo) {
        String extName = fileInfo.getExtName();

        String contextType;
        if ("jpg".equalsIgnoreCase(extName)) {
            contextType = MediaType.IMAGE_JPEG.toString();
        } else if ("png".equalsIgnoreCase(extName)) {
            contextType = MediaType.IMAGE_PNG.toString();
        } else if ("jpeg".equalsIgnoreCase(extName)) {
            contextType = MediaType.IMAGE_JPEG.toString();
        } else {
            return;
        }
        compressionImage(imgPxs, fileInfo, contextType);
    }

    public void compressionImage(String imgPxs, FileInfo fileInfo, String contextType) {
        ImgCompressionPxs pxs = new ImgCompressionPxs(imgPxs);
        if (ZYListUtils.isEmptyList(pxs)) {
            return;
        }

        for (ImgCompressionPx px : pxs) {
            InputStream objectStream = fileStoreService.getObjectStream(fileInfo.toFileWrapper());
            if (null != objectStream) {
                doCompress(objectStream, fileInfo, px, contextType);
            }
        }
    }

    private void doCompress(InputStream objectStream, FileInfo fileInfo, ImgCompressionPx px, String contextType) {
        // 创建BufferedImage对象并加载原始图像数据
        ByteArrayOutputStream exchangeStream = null;
        InputStream expressImgInputStream = null;
        try {
            BufferedImage originalImage = ImageIO.read(objectStream);
            // 设置目标图片大小（这里将图片按比例缩放为50%）
            int targetWidth = (px.getWidth());
            int targetHeight = (px.getHeight());

            // 创建新的空白图像对象
            BufferedImage compressedImage = new BufferedImage(targetWidth, targetHeight, originalImage.getType());

            // 获得Graphics2D对象，用于操作图像55
            Graphics2D g2d = compressedImage.createGraphics();

            // 设置插值算法为双线性插值，提高图像质量
            g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);

            // 绘制缩放后的图像到compressedImage上
            g2d.drawImage(originalImage, 0, 0, targetWidth, targetHeight, null);
            g2d.dispose();

			// 转成字节流,然后字节转成输入流
            exchangeStream = new ByteArrayOutputStream();
            ImageIO.write(compressedImage, fileInfo.getExtName(), exchangeStream);

            byte[] bytes = exchangeStream.toByteArray();

            expressImgInputStream = new ByteArrayInputStream(bytes);
			
			// 包装下上传对象
            FileWrapper fileWrapper = new FileWrapper();
            fileWrapper.setInputStream(expressImgInputStream);

            String expressImgId = px.getPx() + COMPRESS_SEPARATOR + fileInfo.getId();
            fileWrapper.setId(expressImgId);
            fileWrapper.setExtName(fileInfo.getExtName());
            fileWrapper.setNewFileName(expressImgId + ZYStrUtils.DOT + fileInfo.getExtName());
            fileWrapper.setFileSize(fileInfo.getFileSize());
            fileWrapper.setOriginalFilename(fileInfo.getNewFileName());
            fileWrapper.setContentType(contextType);
            // 上传图片，此处用的是minio,不再展示细节了
            fileStoreService.upload(fileWrapper);
			// 保存文件基本信息
            FileInfo compressFileInfo = new FileInfo(fileWrapper);
            compressFileInfo.setIsKeepAlive(YES);
            fileInfoMapper.insert(compressFileInfo);

        } catch (Exception e) {
            log.warn("图片压缩失败" + e.getMessage());
        } finally {
            IoUtil.close(objectStream);
            IoUtil.close(exchangeStream);
            IoUtil.close(expressImgInputStream);
        }
    }
}

ImgCompressionPxs 类：

	@Data
	public class ImgCompressionPxs extends ArrayList<ImgCompressionPx> {
	
	    public ImgCompressionPxs(String imgPxs) {
	        if (ZYStrUtils.isNull(imgPxs)) {
	            return;
	        }
	        // 100*200,200*400,400*600
	        List<String> pxs = ZYListUtils.str2List(imgPxs);
	
	        for (String px : pxs) {
	            this.add(new ImgCompressionPx(px));
	        }
	    }
	}
	
    @Data
    public static class ImgCompressionPx {

        private String px;

        private Integer width;

        private Integer height;

        public ImgCompressionPx(String px) {
            String[] xes = px.split("x");
            if (xes.length != 2) {
                throw new LocalException("压缩图片尺寸有误");
            }
            String widthStr = xes[0];
            String heightStr = xes[1];

            this.px = px;
            this.width = ZYNumberUtils.toInt(widthStr);
            this.height = ZYNumberUtils.toInt(heightStr);
            if (null == this.width || null == this.height) {
                throw new LocalException("压缩图片尺寸有误");
            }
        }
    }