Resized large images for the thumbnails when needed

[Alterrien]

This PR is not to be merged right now, I'm waiting for more feedback on how the different thumbnails look on different sized screens (if somebody has a 2k-plus monitor, he's welcome to give some feedback)
I've resized the thumbnails to 854x480 using convert $file -resize 854x480 $newfile, which should give good enough results. Other solutions could be tried.

Cheers !

Resolves #59

[Wonskcalb]

Tested on my Oneplus 2 5.5" 1920*1080 display, and although layout is broken on small displays, stills render correctly.

[Alterrien]

Paging @aubincleme for input (especially for this : should we be keeping the larger-size images ?)

[aubincleme]

854x480 should be a good resolution

[aubincleme]

I think that larger-size images should be kept somewhere else, without weighing this repository.

[Wonskcalb]

cdn.atilla.org ?

[Wonskcalb]

This will let us to serve multiple size

[aubincleme]

Nope, it’s also another repository, it’s the same problem ; I think that we should keep the original images in where we actually store them (drive.google.com), and diffuse them only if needed.

[Wonskcalb]

I do not agree on this. This website will certainly need a some point higher DPI version of those images if the website is shown on a high DPI screen

[aubincleme]

Ok, let’s make some calculations here :

• Let’s consider that the industry standard in terms of screen resolution is 4K (even if it’s not the case at all)
• We can display about 10 conference / talk / author «rows» on a 4K screen
• In each row, the thumbnail takes about 1/12 of the page width
• The native 4K resolution is 4 096 × 2 160

With all this, we can calculate an approximation of the minimal resolution of a thumbnail in this configuration :

4096 * (1/12) ~= 340
2160 * (1/10) = 216

There you have it, in order to be correctly displayed on a 4K screen, a thumbnail should have a resolution greater than 340*216

So,
Will the website need high-DPI thumbnails at some point ? Maybe
Should we prepare for this ? Certainly not ; we will be able to add high-DPI images in the future anyway.

[Wonskcalb]

I'm not telling do this now. Certainly not. Re-read what I've written. I just meant to say the cdn will be the way to go. It is supposed to, in any matter. I've proposed the High-DPI version here #60. Period.

[Alterrien]

So, we actually need to come to a decision : I guess the image resolution is good, but what will we do with the higher-res images ? Do we have a backup of them somewhere else ? Could we use our OwnCloud to store them ?

[Wonskcalb]

We already have backups of those images oh the Google drive of the comm team. We can delete those safely

[Alterrien]

Alright, I'll delete the Hi-res files and merge after lunch.

[Wonskcalb]

I can do this right now, it won't take long