数据URI - 如何在Java中创建它们？

image java data-uri

2022-09-02 21:29:01

我刚刚被告知使用数据URI发送图像的缩略图。我一直在搜索它，但我发现的只是它基本上是文件的文本表示，可以直接在HTML中使用。我真的找不到如何在Java中制作数据URI。我有一个文件的输入流。有人可以对此有所了解，并指出一种生成它的方法吗？

答案 1

例如，对于图像：

ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
    ImageIO.write(image, "png", baos);
} catch (IOException e) {
    e.printStackTrace();
}
String imageString = "data:image/png;base64," +
    Base64.getEncoder().encodeToString(bytes);

例

运行下面的代码。如果 FF 是默认浏览器，您可能会看到如下内容：

Data URI image in FF

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import java.util.Base64;

public class DataUriConverter {

    static String getImageAsString(BufferedImage image) throws Exception {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        // serialize the image
        ImageIO.write(image, "png", baos);
        // convert the written image to a byte[]
        byte[] bytes = baos.toByteArray();
        System.out.println("bytes.length " + bytes.length);
        // THIS IS IT! Change the bytes to Base 64 Binary
        String data = Base64.getEncoder().encodeToString(bytes);
        // add the 'data URI prefix' before returning the image as string
        return "data:image/png;base64," + data;
    }

    static BufferedImage getImage() {
        int sz = 500;
        BufferedImage image = new BufferedImage(
                sz, sz, BufferedImage.TYPE_INT_ARGB);

        // paint the image..
        Graphics2D g = image.createGraphics();
        g.setRenderingHint(
                RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        g.setColor(new Color(0,0,255,63));
        g.setStroke(new BasicStroke(1.5f));
        for (int ii = 0; ii < sz; ii += 5) {
            g.drawOval(ii, ii, sz - ii, sz - ii);
        }
        g.dispose();

        return image;
    }

    public static void main(String[] args) throws Exception {
        String imageString = getImageAsString(getImage());
        String htmlFrag = "<html><body><img src='%1s'></body></html>";
        String html = String.format(htmlFrag, imageString);

        // write the HTML
        File f = new File("image.html");
        FileWriter fw = new FileWriter(f);
        fw.write(html);
        fw.flush();
        fw.close();

        // display the HTML
        Desktop.getDesktop().open(f);
    }
}

答案 2

这是我的例子。

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;

import javax.xml.bind.DatatypeConverter;

public class ToDataURI {

    public static void main(String[] args) throws IOException {

        // source file
        File file = new File("movie.mp4");

        // check content type of the file
        String contentType = Files.probeContentType(file.toPath());

        // read data as byte[]
        byte[] data = Files.readAllBytes(file.toPath());

        // convert byte[] to base64(java7)
        String base64str = DatatypeConverter.printBase64Binary(data);

        // convert byte[] to base64(java8)
        // String base64str = Base64.getEncoder().encodeToString(data);

        // cretate "data URI"
        StringBuilder sb = new StringBuilder();
        sb.append("data:");
        sb.append(contentType);
        sb.append(";base64,");
        sb.append(base64str);

        System.out.println(sb.toString());

    }
}

加工流程

检查文件内容类型
将文件数据读入字节[]
将字节 [] 数据转换为 base64
创建“数据 URI”格式

你可以得到像

data:video/mp4;base64,AAAAIGZ0eXBpc29tAAACAGlzb21p....