Oops, if we read in a char type, it's assumed to be a character. So read into a temporary integer first.
And set the whole structure as 'defined' after reading in.
Check the WebP encoder config structure and throw an error if it doesn't pass.
Tweak the status messages.
Get a little more robust in parsing chunks as they're being emitted - the lossless WebP encoder does things a little differently.
Set WebP options for previews and converted scans.
Set the 'use_argb' flag if we're writing a lossless WebP image.
For some reason the alpha channel is thrown away when we do lossless.