Your photo must be 600px by 600px with a correct head size and correct distance between eye line and the bottom of the photo, but it also must not be greater than 240 KB in size.
Visafoto.com knows all the visa photo requirements for various countries and does everything automatically in seconds. It crops the picture and correctly scales it, so the head size is correct and all distances are right. It fixes background, fixes head tilt, image contrast, and besides all of these, it makes sure that the result photo does not exceed 240KB.
So if you have your photo ready, you can convert it to a correct passport or visa photo right now at visafoto.com.