Whereas before imaging 2.1 (in Magnolia 4.3.8) it was possible to set the outputFormat for a generator chain, the outputFormat node is seemingly ignored in imaging 2.1.

It seems that the output format is now always taken from the source image.

This makes it impossible to override the output format for a given generator, which is a feature that we are using.

Note also:

it would actually be preferable to set the outputFormat on the variation definition (in the theme) rather than for the whole generator chain.
In this way magnolia would be flexible - different outputFormats could be specified for different variations, and if none is specified, the source image format is used.

That would be ideal.