I understand that you are using an HP Officejet 4500 All-in-One Printer with a Mac that you have recently upgraded to OS X 10.11 El Capitan and picture you scanned did not come out when you attached it to an email. I would like to help with that.
Are you able to use the HP Easy Scan App to scan and save the picture to your Mac? If you need assistance with scanning this document can help - How to Scan to a Mac (OS X).
I will watch for your reply so I can look into this further for you. Please reply at your convenience.
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