Add ability to enable full JPEG baseline compatibility about mozjpeg-rust HOT 2 OPEN

I'm assuming this is only about baseline quantization tables, not disabling progressive rendering.

It would be good to generate 8-bit tables indeed.

If I recall correctly 16-bit tables are generated only when necessary. If values fit in 8 bit, libjpeg-turbo will output 8-bit even if baseline wasn't requested. And values exceed 255 only at qualities lower than 30 or so (depending on qtable), so I'm not sure if that's a widespread problem.

I see two solutions:

1. From API perspective, a separate set_baseline() seems nicer. It would be trickier to change though, because the Rust side would have to "buffer" the settings in case quality is was first. But maybe that's a good thing anyway, given how fragile internal state of libjpeg is.

2. Don't add any option. Automatically force baseline qtables for qualities > 30. Below 30 JPEG falls apart anyway, so nobody should be using these.

from mozjpeg-rust.

I'm assuming this is only about baseline quantization tables, not disabling progressive rendering.

Exactly, this is what I meant. Progressive rendering is not an issue.

If I recall correctly 16-bit tables are generated only when necessary. If values fit in 8 bit, libjpeg-turbo will output 8-bit even if baseline wasn't requested. And values exceed 255 only at qualities lower than 30 or so (depending on qtable), so I'm not sure if that's a widespread problem.

I'm not very familiar with libjpeg-turbo implementation, but I also recall that it uses 8-bit tables when all values are in range 1..255.

I see two solutions:

1. From API perspective, a separate set_baseline() seems nicer. It would be trickier to change though, because the Rust side would have to "buffer" the settings in case quality is was first. But maybe that's a good thing anyway, given how fragile internal state of libjpeg is.

2. Don't add any option. Automatically force baseline qtables for qualities > 30. Below 30 JPEG falls apart anyway, so nobody should be using these.

Latter is easy to implement, while I agree that the former may be a better solution.

from mozjpeg-rust.