Comments on some functions in Sub-Graphics.php

[VBGAMER45]

Ran into an issue today in a gallery modification which created thumbnails.
Issues were with thumbnails for bmp images were not working. I checked some of code and notified a couple things.

First the createThumbnail($source, $max_width, $max_height) function does have a way to set the preferred format ie gif,jpeg,png
I would suggest another parameter for that. In my case had to create my own version of that function to do it correctly.

Next the function
function resizeImageFile($source, $destination, $max_width, $max_height, $preferred_format = 0)

Has notes that say the preferred format (0 to use jpeg, 1 for gif, 2 to force jpeg, 3 for png, 6 for bmp and 15 for wbmp)
But yet does not have code to do so. Only has options for gif,png and jpeg which is the default.
imagebmp and imagewbmp functions are not included and not an option.
Would suggest either to add support for those image functions. Maybe future proof with support for imagewebp as well.

I would tag this for after final probably though.

[albertlast]

About the webp support see #6271

[Sesquipedalian]

I don't see a lot of need to support BMP for thumbnail images. The whole point of thumbnails is to save bandwidth, after all, so why on earth would anyone store them in BMP format?

The second part of this issue makes sense to me, though.

[Sesquipedalian]

Please test to confirm that #7355 fixes this issue (or rather, the second part of this issue).

[albertlast]

Why not #6271 ?

[Sesquipedalian]

Why not #6271 ?

As @sbulen mentioned in the comments on that PR:

Note that IMAGETYPE_WEBP is only defined in php 7.1+.

We support PHP 7.0, so not an option yet.