In my old phone, when I am copying a link. It has "m" instead of "i". Just like this (
http://m.imgur.com/DZDpUfu.jpg) so I usually change it to letter "i" (
https://i.imgur.com/DZDpUfu.jpg). If you encounters like that, just try to change the letter "m" of letter "i".
Secondly. Just like what bL4nkcode also said, it needs to put "s" in {http://}
I am an imgur user and I usually uploaded it here before I am using the bbcode here. Recently, I cannot post pictures because it says invalid. Eventhough I did the 1st and 2nd tip in changing.
What I did?
I downloaded the imgur app in my phone, I created an account here and sign in.
Follow this steps:
Open the imgur app, then click the upload button. It shows below.
Next, click desired picture from your gallery and select "next"
Next step, you can public or hide your post. I preferred to select hidden and select "Upload".
Next, wait for your picture/s to upload. Then, go to your profile and look for your upload picture/s.
Here is the tricky part because I realized that copying the link in upper left part of screen gave me an invalid picture.
So what I do? I press the picture (long press) until this appear.
When it appears, select the "copy url" and it will give you the correct bb code.
I hope it helps you.