ausboss-ComfyUI-AusBoss/js/docs/AUSBOSS_NODES_RealignToSource.md

Realign to Source (EXPERIMENTAL)

Undoes the zoom and shift an edit model adds to a broad edit. Wire the edit into edited and the picture it was made from into source: the node measures where the edit's content sits against the source and warps the edit back onto the source's frame, at the source's size, in one resample.

Experimental. It is measured on Qwen Image 2.1 edits and planted drifts, not yet on other edit models. Its sockets and settings keep their names from here on; how it measures may still improve.

Why

Qwen Image 2.1 redraws a broad edit with slightly different proportions. Watercolor, anime and oil edits come back about 4% taller on average and up to 12%: 30-40 px at the edges of a 1 MP picture, up to 90. It changes with the seed and the prompt, and snapping sizes to 32, 64 or 112 does not help. Light edits (a colour change, "keep it the same") hold within 0.4%. Sampling on the Qwen encoder's own latent output matters too: a canvas of another size makes the model shrink the whole picture to fit inside it, which is a separate zoom this node is not meant to undo.

What it fixes, and what it doesn't

• Fixes: the whole-frame zoom (separately across and down) and shift, so the edit sits on the source's frame again: horizons, posts and faces land back where they were.
• Doesn't fix: shapes a restyle redrew in a new place. A watercolor that moved a boat or widened a face keeps that change, so the result lines up closely, not pixel for pixel.
• Leaves alone: a frame it cannot measure, such as a picture with too little shared structure, a zoom past Max zoom, or an edit made on a canvas of another shape. That frame is only scaled to the source's size, its empty_mask is all black, and report says why.

Controls

• edited: The edit, at any size. It is compared as if scaled to the source's exact size, which also undoes the Qwen 2.1 encoder's stretch to its 32 px grid. An alpha channel is ignored; the output is RGB.
• source: The picture the edit was made from, at the size the model saw it (in the Qwen Image 2.1 Edit + Realign example, the Image Resize output). One frame, or one per edited frame. The result comes out at this size.
• Fit (fit):
  • zoom + shift: a horizontal and a vertical zoom plus a shift, which is how Qwen edits drift. The default.
  • affine: also a slight rotation or shear.
• Empty fill (empty_fill): what the strip with no content shows. The model pushed that strip out of view, so the edit has nothing for it.
  • edge: stretches the nearest edge pixels. The default.
  • source: the original's pixels.
  • gray: flat #808080, for an inpaint pass.
• Max zoom (max_zoom): the largest zoom, in percent, it will undo; 20 by default. Past it the edit most likely changed the framing on purpose, so the frame is left as it is.

Outputs

• image: The edit on the source's frame, at the source's size.
• empty_mask: White where the realigned edit has no content: the strip the model pushed out of view, along the top and bottom for a vertical stretch. On the style edits measured it was 4.4% of the frame at the median and 10.5% at the 90th percentile. Crop it off or inpaint it. All black for a frame that was left as it is.
• report: One line per frame (prefixed frame N: for a batch). The watercolor in the Qwen Image 2.1 Edit + Realign example reads realigned: zoom x +0.46%, y +6.64%; shift x +0.1, y +0.9 px; worst corner 41.3 px (59 of 150 areas agree, fit error 3.3 px); empty strip 6.7% of the frame. The zoom is per axis, the shift is measured at the picture's centre, and the worst corner is how far the worst of the four corners had moved. Wire it to Show Text 🆎 to read it.

How it measures

Both pictures become edge maps (gradient strength, normalised by its surroundings), so a restyle, a relight or inverted tones still line up. Blocks are compared by band-limited phase correlation: first at 256 px on the long side to find the drift, then twice at 768 px after warping the edit by the estimate, so the blocks are compared at the same scale. A robust fit turns the block shifts into the zoom and shift; blocks that disagree with it by more than a few pixels (8 at most), such as a redrawn boat or a new cloud, are left out. It trusts the fit when at least 10 blocks, and at least a quarter of them, agree.

It runs on the CPU in a fraction of a second per 1 MP frame. No new dependencies, and no model.

Tips

• Keep the sampler on the Qwen encoder's latent output, and feed the same picture the encoder saw into source.
• The drift changes with every seed. If the empty strip is too wide to crop, another seed often drifts less.
• The report is worth a glance on light edits: a zoom under 0.5% means the model held the frame and the node changed next to nothing.

Measured

• Planted drifts (zoom up to 12% per axis, shifts, a slight rotation with affine, restyled copies, edits at another resolution): recovered within about 0.1 px at the corners.
• 166 real Qwen Image 2.1 edits of four pictures at the Qwen 2.1 Edit example's settings: 164 measured. The two it left alone were sampled on a 1024x1024 canvas for an 832x1216 picture (the wrong-canvas squeeze), and the report names that. Re-measured by a separate estimator after realigning, the worst corner of the 94 style edits went from 35.5 px to 4.6 px (median); light edits from 2.1 px to 0.1 px.