Write Base64-encoded image to file

Question

How to write a Base64-encoded image to file?

I have encoded an image to a string using Base64. First, I read the file, then convert it to a byte array and then apply Base64 encoding to convert the image to a string.

Now my problem is how to decode it.

byte dearr[] = Base64.decodeBase64(crntImage);
File outF = new File("c:/decode/abc.bmp");
BufferedImage img02 = ImageIO.write(img02, "bmp", outF); 

The variable crntImage contains the string representation of the image.

Answer 1

With Java 8's Base64 API

byte[] decodedImg = Base64.getDecoder()
                    .decode(encodedImg.getBytes(StandardCharsets.UTF_8));
Path destinationFile = Paths.get("/path/to/imageDir", "myImage.jpg");
Files.write(destinationFile, decodedImg);

If your encoded image starts with something like data:image/png;base64,iVBORw0..., you'll have to remove the part. See this answer for an easy way to do that.

Answer 2

No need to use BufferedImage, as you already have the image file in a byte array

    byte dearr[] = Base64.decodeBase64(crntImage);
    FileOutputStream fos = new FileOutputStream(new File("c:/decode/abc.bmp")); 
    fos.write(dearr); 
    fos.close();

Answer 3

import java.util.Base64;

.... Just making it clear that this answer uses the java.util.Base64 package, without using any third-party libraries.

String crntImage=<a valid base 64 string>

byte[] data = Base64.getDecoder().decode(crntImage);

try( OutputStream stream = new FileOutputStream("d:/temp/abc.pdf") ) 
{
   stream.write(data);
}
catch (Exception e) 
{
   System.err.println("Couldn't write to file...");
}

Answer 4

Other option using apache-commons:

import org.apache.commons.codec.binary.Base64;
import org.apache.commons.io.FileUtils;

...
File file = new File( "path" );
byte[] bytes = Base64.decodeBase64( "base64" );
FileUtils.writeByteArrayToFile( file, bytes );