Cannot properly decode Base64 MIME image to byte array (Java)

Question

I'm trying to write some selenium/java test that checks 2FA configuration process. Thus I have to scan some QR code from a page in order to process it with zxing. The image format is Base64 and I'm struggling with decoding it to the byte array. The following code should convert base64 string to byte array, and then write it to the file.

Here is the code I wrote:

String base64Source = LocalDriverManager.get().findElement(By.xpath("//img[@class='qr-code']")).getAttribute("src");
String base64Image = base64Source.split(",")[1];
byte[] decoded = Base64.getMimeDecoder().decode(base64Image);

try (OutputStream stream = new FileOutputStream("QR_CODE.png")){
                stream.write(decoded);
            }

This code compiles with no errors, but when I try to open generated png file I get only "Fatal error reading PNG image file: Decompression error in IDAT". I know that base64 string is valid as I was able to convert it to the image using some online converter. Also, I checked the string with online validator and it said that this is a valid base64 MIME string. Example of the base64 code below:

iVBORw0KGgoAAAANSUhEUgAAAeoAAAHqAQAAAADjFjCXAAAET0lEQVR4nO2dXYrrOgyAP50E5jGB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%0AFuoX02DU2vMAAAAASUVORK5CYII=

Succesfully converted to img with this: codebeautify.org/base64-to-image-converter And valided as MIME standard with this tool: base64.guru/tools/validator — turbotramp

Mega Mbo Mega Mbo · Accepted Answer · 2019-04-29T13:15:30

try this

String base64Source = LocalDriverManager.get().findElement(By.xpath("//img[@class='qr-code']")).getAttribute("src");
String base64Image = base64Source.split(";")[1].split(",")[1]; //Try this
byte[] decoded = Base64.getMimeDecoder().decode(base64Image);

try (OutputStream stream = new FileOutputStream("QR_CODE.png")){
                stream.write(decoded);
            }

Cannot properly decode Base64 MIME image to byte array (Java)

2 Answers