Otherwise, e.g. if a message is a large GIF, but its viewtype is set to `Image` by the app, this GIF
will be recoded to JPEG to reduce its size. GIFs and other special viewtypes must be always detected
and sent as is.
Check if a sticker has at least one fully transparent corner and otherwise change the Sticker type
to Image. This would fix both Android and iOS at the same time and prevent similar bug on future
platforms that may get this bug like Ubuntu Touch.
I.e. > 500K for the balanced media quality and 130K for the worse one. This can remove animation and
transparency from PNG/WebP, but then a user always can send an image as a file.
Also don't reduce wide/high images if they aren't huge. Among other benefits, this way most of PNG
screenshots aren't touched.
Also remove Exif from all images, not from JPEGs only.
