I am writing an experimental project in VB.net to modify the colour data in a picture.
I've finished the simple version using BMP file and now want to add JPEGs

From what I read the JPEG compression uses the Discrete Cosine function which (if I understand the process) effectively compares pixels in successive 8x8 grids to produce a smooth "averaging" of the colours in that area to reduce the number of colours used which then allows RLE pixel count to store the data in the same way as TIFF

I admit - trying to work the DCF without using pre-written libraries is way beyond my maths skills... So I want to attack the data store, avoid the complexity of the DCF function and just tinker with the colour values (lighten, darken, enrich, sepiarise)

It may not work, but I'd like to try.

Assuming I'm right in my supposition, can anyone help with the Image start point and the format of the image data.