A utility class to convert Bitmap image to Base64 and vice versa.

ImageUtil.java

public class ImageUtil {
    /**
     * 
     * @param base64Str Base64 string for the image.
     * @return Bitmap value for the image.
     * @throws IllegalArgumentException
     */
    public static Bitmap convert(String base64Str) throws IllegalArgumentException {
        byte[] decodedBytes = Base64.decode(
                base64Str.substring(base64Str.indexOf(",") + 1),
                Base64.DEFAULT
        );

        return BitmapFactory.decodeByteArray(decodedBytes, 0, decodedBytes.length);
    }

    /**
     * 
     * @param bitmap Bitmap image to be converted to base64
     * @return Base64 String for the bitmap passed as paramater
     */
    public static String convert(Bitmap bitmap) {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, outputStream);

        return Base64.encodeToString(outputStream.toByteArray(), Base64.DEFAULT);
    }

}