Improve image preview quality

[darktorres]

As demonstrated in the link: https://docs.rs/image/latest/image/imageops/enum.FilterType.html

[alexislefebvre]

Bilinear doesn't appear on the link or when searching in the doc: https://docs.rs/image/latest/image/imageops/enum.FilterType.html?search=Bilinear

How does it work?

[darktorres]

The manual for the change I made is in here:
https://docs.gtk.org/gdk-pixbuf/enum.InterpType.html
The first link is only for the images examples.

[darktorres]

Gdk Bilinear is closest to imageops Triangle

[darktorres]

I made a before/after in czkawka:

[qarmin]

What is time difference in loading big images?
The main reason why I choose such resizing algorithm is quite big loading/resizing times of files with >10 millions pixels.
If such times are too big, then only smallest files should be used to resized with this algorithm

[darktorres]

There is a increase in time but I would say it's small considering the time spent loading the pixbuf.

Big image 124MP	Nearest	Bilinear
Load pixbuf	1389ms	1393ms
Resize pixbuf	23ms	199ms

Average image 1.3MP	Nearest	Bilinear
Load pixbuf	12ms	11ms
Resize pixbuf	0ms	9ms

[God-damnit-all]

It seems like it makes more sense to keep using nearest, the preview is just supposed to give you a rough idea of what you're working with, right?

[alexislefebvre]

@ImportTaste With this PR, it should be easier to compare similar images since there will be less resizing artifacts in the previews of images.

[qarmin]

Thanks!