I believe the instructions you linked differ slightly from the eAPR photo in that they specify dimensions of 50x70mm minimum-- the eAPR photo needs to be 35x45mm minimum, which is a slightly different proportion. When you get your document checklist for eAPR, it will include detailed photo instructions and that's what you should use; the instructions are as follows:
Frame size
- The final frame size of the photo must be at least 35mm x 45mm.
- The photographs must show a full front view of the head and tops of shoulders, with the face in the middle of the photograph.
- The size of the head, from chin to crown, must be between 31mm and 36mm.
- Digital dimensions are often expressed in pixels or DPI (dots per inch). The physical dimensions in pixels must be at least 420 x 540.
Quality/resolution
If an existing photo is being scanned, the minimum resolution must be 600 pixels per inch.
File format
- The file may be submitted in JPEG or JPEG2000 format.
- The final size of the image should ideally be 240 kB (kilobytes), but not less than 60 kB.
- The image must be in colour (24 bits per pixel) in RGB colour space, which is the common output for most digital cameras.
Also, I think the same specifications are available here:
http://www.cic.gc.ca/english/information/applications/photospecs.asp
Apparently the photo specs for visa applications differ from those for permanent residence, and for eAPR they use the
visa photo specs, not the PR specs-- very confusing! Walgreen's will create a photo using the PR specs, so you'll need to adjust it to meet the visa/eAPR specs.