Most of us keep our pictures on the phone. If you send a photo stored in the phone gallery, send the photo from the place where it was saved. Don’t take a screenshot! Screenshot is not the picture itself and its real size is reduced. You can see how it works in the attached example:
CAMERA 9,4MP 23004 x 4096 3,1MB
vs
SCREENSHOT 1,1MP 720 x 1520 1,2MB