You also....

Need to understand logical mathematics. Especially, working with binary, and hexedecimal numbers. So, bone up on you eigth grade math (in the US, this is taught in the eight grade). Without this, you probably won't understand the turning on/off of pixels.

Need to understand Algebra. I mean really really understand algebra. This is not too important, if you are not writing your own graphic library, but it is critical, if you are writing or modifying one. Raster graphics calculations are all done with algebra.

Neet to understand Geometry. Nuff said....

And as already mentioned, other maths are important too. There is some good news... I have never found the need to use my Calculus skills when working with graphics...

Henry