Write Base64-encoded image to file

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.

Assuming the image data is already in the format you want, you don't need ImageIO at all - you just need to write the data to the file:

// Note preferred way of declaring an array variable
byte[] data = Base64.decodeBase64(crntImage);
try (OutputStream stream = new FileOutputStream("c:/decode/abc.bmp")) {
    stream.write(data);
}

(I'm assuming you're using Java 7 here - if not, you'll need to write a manual try/finally statement to close the stream.)

If the image data isn't in the format you want, you'll need to give more details.

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();