How to set padding for base64 encoding

[Suliman via Digitalmars-d-learn]

It's look like my data have padding that cause crush on 
function:	std.file.write("output.png", Base64.decode(myimg));
> Invalid character:

It's look like I should to use template function, but I can't 
figure out how to use it. Could anybody show example?

My code:
http://www.everfall.com/paste/id.php?pzpdgvtyb3ji

https://dlang.org/phobos/std_base64.html#.Base64