Each of these was a bit off:
- The SD callback started at `-1` and ended at `i`. Combined w/ the weird math on the previous `calc_percentage` util, this caused the progress bar to never finish.
- The MultiDiffusion callback had the same problems as SD.
- The FLUX callback didn't emit a pre-denoising step 0 image. It also reported total_steps as 1 higher than the actual step count.
Each of these now emit the expected events to the frontend:
- The initial latents at 0%
- Progress at each step, ending at 100%
- Update the step callback methods in the invocation API to use the new signal_progress API
- Copy and update the `calc_percentage`, reducing special handling for step and total_steps - a followup commit will fix callers of the step callbacks
## Summary
This PR makes some improvements to the FLUX image-to-image and
inpainting behaviours.
Changes:
- Expand inpainting region at a cutoff timestep. This improves seam
coherence around inpainting regions.
- Add Trajectory Guidance to improve the ability to control how much an
image gets modified during image-to-image/inpainting (see the code for a
more technical explanation - it's well-documented).
## `trajectory_guidance_strength` Usage
- The `trajectory_guidance_strength` param has been added to the `FLUX
Denoise` invocation.
- `trajectory_guidance_strength` defaults to `0.0` and should be in the
range [0, 1].
- `trajectory_guidance_strength = 0.0` has no effect on the denoising
process.
- `trajectory_guidance_strength = 1.0` will guide strongly towards the
original image.
## FLUX image-to-image usage tips
- As always, prompt matters a lot.
- If you are trying to making minor perturbations to an image, use
vanilla image-to-image by setting the `denoising_start` param.
- If you are trying to make significant changes to an image, using
trajectory guidance will give more control than using vanilla
image-to-image. Set `denoising_start=0.0` and adjust
`trajectory_guidance_strength` to control the amount of change in the
image.
- The 'transition point' where the image changes the most as you adjust
`trajectory_guidance_strength` or `denoise_start` varies depending on
the noise. So, set a fixed noise seed, then tune those params.
## QA Instructions
- [x] Vanilla image-to-image - No change in output
- [x] Vanilla inpainting - No change in output
- [x] Vanilla outpainting - No change in output
- Trajectory Guidance image-to-image
- [x] TGS = 0.0 is identical to Vanilla case
- [x] TGS = 1.0 guides close to the original image
- Not as close as I'd like, but it's not broken.
- [x] Smooth transition as TGS varies
- [x] Smoke test: TGS with denoise_start > 0.0
- TG inpainting
- [x] TGS = 0.0 is identical to Vanilla case
- [x] TGS = 1.0 guides close to the original image
- Not as close as I'd like, but it's not broken
- [x] Smooth transition as TGS varies
- [x] Smoke test: TGS with denoise_start > 0.0
- TG outpainting
- [x] TGS = 0.0 is identical to Vanilla case
- [x] Smoke test TGS outpainting
- [x] Smoke test FLUX text-to-image
- [x] Preview images look ok for all of above.
## Known issues (will be addressed in follow-up PRs)
- The current TGS scale biases towards creating more change than desired
in the image. More tuning of the TG change schedule is required.
- TGS does not work very well for outpainting right now. This _might_ be
solvable, but more likely we'll just want to discourage it in the Linear
UI.
## Merge Plan
No special instructions.
## Checklist
- [x] _The PR has a short but descriptive title, suitable for a
changelog_
- [x] _Tests added / updated (if applicable)_
- [x] _Documentation added / updated (if applicable)_
