Support ICO files in image preview

[Denisov21]

I would like Brackets could also view the *. ICO, as similar with *.JPG files.
I'd like to see a preview of the ICO file on Brackets. I thought to see this image. As regards the actual size on the screen is not interested, I thought you could only see the larger image. I hope someone can implement this feature. Currently I do not know Javascript API that can do this!

[Denisov21]

Can you merge this #7018? Thank you. Sorry for error!!

[peterflynn]

If we only want to show the largest size in the ICO file, this is probably a 'starter bug' because the browser preview seems to select the largest size automatically.

I'd be concerned though that that's not very useful functionality for most people -- typically ICO files contain multiple sizes, with the largest size being one of the least frequently used. Showing all the sizes would be a big 'move to backlog' since it would require parsing the ICO binary.

[peterflynn]

Related forum thread: https://groups.google.com/forum/#!topic/brackets-dev/hkYFFPB4lQc

[marcelgerber]

@peterflynn I'd suggest to first implement showing just the largest one - that's at least better than nothing.
We can add more functionality later on.

[peterflynn]

Fair enough. Marking 'starter bug' for someone to just add .ico to the image file type list and see how well it works!

[marcelgerber]

It works. Should we do unit tests or show a hint (only the biggest icon of the .ico is shown. There may be other ones included.)?

[peterflynn]

We don't have unit tests for any of the other ImageViewer stuff, so probably no tests needed for now (unless you want to write a bunch of them :-)

I like the idea of adding a label explaining the size caveat (although I'd maybe say "largest" instead of "biggest"). @larz0 any thoughts on label placement, wording, etc.?

[larz0]

@peterflynn @SAplayer for the format we could try "256 × 256 pixels (largest) — 700 KB"

[peterflynn]

Cleaned up title (was "New wish in Brackets, open file ICO")