java 通过图片地址 转换图片信息 小于4mb 分辨率不高于4096x4096 如果不符合转化为符合条件的图片 存在MultipartFile

您好！可以使用Java的ImageIO类来读取图片信息，以下是一个简单的代码示例：

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.net.URL;

public class ImageUtils {
    public static BufferedImage readImage(String imagePath) throws IOException {
        URL url = new URL(imagePath);
        BufferedImage image = ImageIO.read(url);
        if (image == null) {
            throw new IOException("Failed to read image from " + imagePath);
        }
        return image;
    }

    public static BufferedImage resizeImage(BufferedImage originalImage, int targetWidth, int targetHeight) {
        int type = originalImage.getType() == 0 ? BufferedImage.TYPE_INT_ARGB : originalImage.getType();
        BufferedImage resizedImage = new BufferedImage(targetWidth, targetHeight, type);
        resizedImage.getGraphics().drawImage(originalImage, 0, 0, targetWidth, targetHeight, null);
        return resizedImage;
    }

    public static byte[] toByteArray(BufferedImage image, String format) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ImageIO.write(image, format, baos);
        return baos.toByteArray();
    }

    public static void main(String[] args) throws IOException {
        String imagePath = "https://example.com/image.jpg";
        BufferedImage originalImage = readImage(imagePath);
        int width = originalImage.getWidth();
        int height = originalImage.getHeight();
        if (width > 4096 || height > 4096 || toByteArray(originalImage, "jpg").length > 4 * 1024 * 1024) {
            // image does not meet the requirements, resize it
            int targetWidth = Math.min(width, 4096);
            int targetHeight = Math.min(height, 4096);
            if (targetWidth != width || targetHeight != height) {
                originalImage = resizeImage(originalImage, targetWidth, targetHeight);
            }
            while (toByteArray(originalImage, "jpg").length > 4 * 1024 * 1024) {
                targetWidth = (int) (targetWidth * 0.9);
                targetHeight = (int) (targetHeight * 0.9);
                originalImage = resizeImage(originalImage, targetWidth, targetHeight);
            }
        }
        byte[] imageData = toByteArray(originalImage, "jpg");
        // save the image data to a file or MultipartFile
        // ...
    }
}

在上述代码中，`readImage()`函数用于从指定的URL读取图片，`resizeImage()`函数用于调整图片大小，`toByteArray()`函数用于将图片转换为字节数组。当读取的图片不符合要求时，通过不断调整大小来使其符合要求。最终得到的图片数据可以保存到一个文件或者MultipartFile对象中。