GTKD Cairo get pixel color

[Basile B. via Digitalmars-d-learn]

On Tuesday, 5 January 2016 at 15:04:57 UTC, TheDGuy wrote:
> But i get "only one index allowed to index char". So it looks 
> like there is no 2D array but just a char.
> If i try like this:

The data is just a contiguous memory area. You have to implement 
your own opIndexAssign()/opIndex() to write/read a pixel at 
[line, column].

This is basically `dataPtr + (line * width + column) * 4`.

---
auto opIndex(size_t line, size_t column)
{
     auto ptr = basePtr + (line * width + column) * 4;
     // return something at "ptr".
}

void opIndexAssign(T)(auto ref T t, size_t line, size_t column)
{
     auto ptr = basePtr + (line * width + column) * 4;
     // assign t at "ptr".
}
---

(assuming format is ARGB, so 32bit, so "*4").