http://www.cic.gc.ca/english/information/applications/photospecs-cit.asp
Specifications:
The frame size must be at least 35 mm x 45 mm (1 3/8″ x 1 3/4″).
The photographs must show the full front view of the head, with the face in the middle of the photograph, and include the top of the shoulders.
The size of the head, from chin to crown, must be between 31 mm (1 1/4″) and 36 mm (1 7/16″).
Crown means the top of the head or (if obscured by hair or a head covering) where the top of the head or skull would be if it could be seen.
If the photographs do not meet the specifications, you will have to provide new photographs before your application can be processed.