More usability issues

[p0nce]

Emulate the imageformats functions as public API.

Main problem is just that I could not be ensured that the order is what I needed
so I needed to add a lot more code to make sure, eg. that all data was interleaved RGB(A)
maybe a toInterleaved8 and toInterleaved16 function pair that does the heavy lifting would make it easier...
together with a format parameter to specify whether conversion to RGB/RGBA should happen

you get:
channel count
bits per channel (8 or 16)
functions for auto-converting to the format you need if need be
Of course, for GPU-side compressed formats I'd rather need the raw binary blob together with width and height

imgformats makes it really easy to get the pixels out

All the extra flags you need to pass does make the API slightly more hard to wrap ones head around I'll be honest

[p0nce]

• channel count function
• bpc function
• easy load function just like in imgfmt
• Advertise more the functions convertTo people don't realize it exist

[p0nce]

comment from Dplug

// Note about gamut: would be way easier to use if there was a way to copy a single channel from another image,
// to fill a single channel with 255, to resize from an image to another, to easily crop a rectangle.

[p0nce]

• easy "toRef" function, to initialize an image as a reference to another. For now, have to use image.layer(0)

[p0nce]

• downallocation should not reallocate down until shrinkToFit is called? Else, it makes reusing a buffer with various size a realtime hazard, much like realloc vs Vec => rare case that would necessitate a .reserve call instead