I have to do some image processing algorithms (noise removal) using Discrete Wavelet Transform (I've implemented Critically Sampled DWT). To do this, I want to

I have to do some image processing algorithms (noise removal) using Discrete Wavelet Transform (I've implemented Critically Sampled DWT). To do this, I want to intuitively understand: what that wavelet function is; why do we need to write integrals (with exponential in complex power!) - thus, why we have to make generalization CWT (Continuous WT) to effectively implement DWT; what parameters can I play with to obtain best result. Now it's black box for me.