For me, it won't be wrong, think of an 8-bit image etc, it depends on the quality of the image that is being saved. Images that are of high quality might require more space and meaningly, more data for each of the pixel notation on the screen, that is why most images in low quality would take 200kb, and in high-quality might take upto 4mb of space.
Different format of images require different space size etc, and covering them all here won't be enough. Understanding the
Digital Image[
^] is the core concept to understand what is an image in computers. Then once this is done, there comes other articles and blogs to explain the concept to store the images in binary format.
http://www.ehow.com/about_6625295_graphics-images-stored-computer_.html[
^]
https://en.wikipedia.org/wiki/Binary_image[
^]
http://pippin.gimp.org/image_processing/chap_dir.html[
^]
Go through these posts, to learn on this topic. I believe, that this can be as semantic as it can be, more the quality of the image, more the size to represent each of the pixel on screen.