Procedural textures : How can I read pixel data from arbitrary pixels

[skitchy]

Is this possible with procedural textures code? Say the procedure is currently operating on pixel (1,2) but I want to know the red values of the pixels at (1,1) ánd (1,3) - how do I get that data?

Is there any sort of array structure I can use to store and index a lot of different values?

Can I directly access the pixel data of the image as an array?

Also is there a way of shifting the entire image or perhaps the current row/column by n pixels procedurally (like "affine" but in code)?

If not then please consider this a feature request.

Edited April 20, 2020 by skitchy

[firstdefence]

1. You could use the Colour Picker Tool (i) in conjunction with the Info Panel, View > Studio: Info Panel this will read out location data and colour information. https://affinity.help/photo/English.lproj/pages/Panels/infoPanel.html 
2. The only Array I can think of would be to create a colour palette from the image. https://affinity.help/photo/English.lproj/pages/Panels/swatchesPanel.html
3. With regards to Affine but in code, you have Filters > Distort: Equations... and also Filters > Colours > Procedural Texture… and you have Procedural Texture... as a Live filter on the Layer panel. You also have the Affine Filter under Filters > Distort: Affine 

[skitchy]

Thanks, but I am specifically looking for the actual code to do it with the "procedural textures" tool. I've updated the question to make it more clear.

[John Rostron]

You can shift pixels using Filters > Distort > Equations, with a similar effect to the Affine Transform (Filters > Distort > Affine), but I cannot see how to use these equations in a Procedural Texture (and I have tried).

The equations I used were:

x=   irem(x+a*w,w)
y=   irem(y+b*h,h)

I have  posted a thread in the Resources forum describing a macro to do this.

John