Roger

As part of the FileOptimiser's optimisation process. The optimised file has the file header modified (and also some other data).

No.... The color type. fileld in the file header is being modified from 0 (GrayScale) to 3 (Indexed channel containing indices into a palette of colors) . The26th byte in this particular file. You can test it out by using a hex editor and changing the 26th byte back to 0 (from 3). There wil be inversion of colours be cause you are not remapping the colour table back. But that is 'proof' that bit-depth is changed.

No.... The color type. fileld in the file header is being modified from 0 (GrayScale) to 3 (Indexed channel containing indices into a palette of colors) . The26th byte in this particular file. You can test it out by using a hex editor and changing the 26th back to 0 (from 3). There wil be inversion of colours be cause you are not remapping the colour table back. But that is 'proof' that bit-depth is changed.

Attached is Before and After. Note I used Photoshop to load the After file, and it was a 8-bit indexed colour file. Some other programs that are just viewers, report it as 1-Bit but that is probably because only 2 colours are used in the image.

Yes. LossLESS.

This is for Version 13.x (can you move it to tha MileStone) and delete THIS message

The approach is to be visually lossless. No, it is to be completly Lossless (not visually), as the Allow Lossy Optimisations option is NOT enabled when this happens.

Unless you want to take it up with the tools authours, ask them to have an option to Allow this to happen, an implement it with the Optimiser.