Iphone user can't receive the picture message from samsung s3 why?

My friend who has the samsug galaxy s3 is trying to send me picture messages to my iphone 4s. But whenever i get the picture message on my iphone 4, it says

A Picture/Video Message!
The image file ___2.png is not supported and was deleted.

Why is this happening? How can we fix this?

I used to be able to see the picture he sends from s3 to my iphone but now i'm not getting anything!

There could be many reasons:
1. The file sent is corrupted
2. The png is not standard encryption.
3. If you are jailbroken some software is coming in between.
4. Maybe iphone 4 does not support the format.
Solutions:
1. Try sending it on Whatsapp
2. Try converting the image format.
3. Try sending it on blue tooh or Wi-Fi direct