在 Java 中使用 Base64 编码来自 URL 的图像

Encode image from URL in Base64 in Java

提问by skunk a

I want to encode and save from an URL images in Base64. I found several example doing the encoding from a local file but not from an URL. Is there a possibility to do that?

我想对 Base64 中的 URL 图像进行编码和保存。我发现了几个从本地文件而不是从 URL 进行编码的示例。有没有可能做到这一点？

I tried something like that, but unsuccessfully. Any clue,help? Thanks for your answer.

我尝试过类似的事情，但没有成功。任何线索，帮助？感谢您的回答。

    public static void main(String[] args)  {
    String imageUrl = "http://www.avajava.com/images/avajavalogo.jpg";
    String destinationFile = "image.jpg";

    try {           
        // Reading a Image file from file system
        URL url = new URL(imageUrl);
        InputStream is = url.openStream();

        FileInputStream imageInFile = new FileInputStream(is.toString());
        byte imageData[] = new byte[2048];
        imageInFile.read(imageData);

        // Converting Image byte array into Base64 String
        String imageDataString = encodeImage(imageData);
        System.out.println("imageDataString : " + imageDataString);




        System.out.println("Image Successfully Manipulated!");
    } catch (FileNotFoundException e) {
        System.out.println("Image not found" + e);
    } catch (IOException ioe) {
        System.out.println("Exception while reading the Image " + ioe);
    }

}

/**
 * Encodes the byte array into base64 string
 *
 * @param imageByteArray - byte array
 * @return String a {@link java.lang.String}
 */
public static String encodeImage(byte[] imageByteArray) {
    return Base64.encodeBase64URLSafeString(imageByteArray);
}

采纳答案by milanboruvka

You should not use FileInputStream.

您不应该使用 FileInputStream。

Use something like:

使用类似的东西：

URL url = new URL(imageUrl);
BufferedInputStream bis = new BufferedInputStream(url.openConnection().getInputStream());

Also you need to read data in loop until you read all bytes of image.

您还需要循环读取数据，直到读取图像的所有字节。

回答by Jesper

Do you understand what this line does?

你明白这条线的作用吗？

FileInputStream imageInFile = new FileInputStream(is.toString());

First it calls toStringon an InputStreamobject. That will result in a string that looks something like: InputStream@23e5aa. Then it tries to open a file with that name. You don't want to read a file named InputStream@23e5aa, so this is totally wrong.

首先它调用toString一个InputStream对象。这将导致看起来像一个字符串：InputStream@23e5aa。然后它尝试打开具有该名称的文件。您不想读取名为 的文件InputStream@23e5aa，因此这是完全错误的。

What you want to do instead is read all the bytes in the original InputStream isinto a byte array. How to do that is explained in the answers to this question:

您想要做的是将原始文件中的所有字节读InputStream is入一个字节数组。在这个问题的答案中解释了如何做到这一点：

Convert InputStream to byte array in Java

在 Java 中将 InputStream 转换为字节数组

回答by Ketan Ramani

Try this function by passing image url in parameter.

通过在参数中传递图像 url 来尝试此功能。

private String getByteArrayFromImageURL(String url) {

    try {
        URL imageUrl = new URL(url);
        URLConnection ucon = imageUrl.openConnection();
        InputStream is = ucon.getInputStream();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int read = 0;
        while ((read = is.read(buffer, 0, buffer.length)) != -1) {
            baos.write(buffer, 0, read);
        }
        baos.flush();
        return Base64.encodeToString(baos.toByteArray(), Base64.DEFAULT);
    } catch (Exception e) {
        Log.d("Error", e.toString());
    }
    return null;
}

回答by shriram

Following code converts image into the base64 string:

以下代码将图像转换为 base64 字符串：

public String getBase64EncodedImage(String imageURL) throws IOException {
    java.net.URL url = new java.net.URL(imageURL); 
    InputStream is = url.openStream();  
    byte[] bytes = org.apache.commons.io.IOUtils.toByteArray(is); 
    return Base64.encodeBase64String(bytes);
}

P.S. Above code uses commons-ioas a dependency.

PS 以上代码commons-io用作依赖项。

回答by HARI HARAN

/**
     *
     * @param url - web url
     * @return - Base64 String
     * Method used to Convert URL to Base64 String
     */
    public String convertUrlToBase64(String url) {
        URL newurl;
        Bitmap bitmap;
        String base64 = "";
        try {
            StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
            StrictMode.setThreadPolicy(policy);
            newurl = new URL(url);
            bitmap = BitmapFactory.decodeStream(newurl.openConnection().getInputStream());
            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, outputStream);
            base64 = Base64.encodeToString(outputStream.toByteArray(), Base64.DEFAULT);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return base64;
    }