ComfyUI-DeGrid

ComfyUI-DeGrid

One node: VAE DeGrid (Nyquist Notch) — removes the 2px pixel grid that the Qwen Image VAE (and, to a lesser extent, the Wan 2.1 VAE) leaves across decoded images. Affects Krea2, Qwen Image, Anima and anything else built on those VAEs.

The artifact is easy to miss at 100% zoom, but it gets amplified by any sharpening or upscaling applied afterwards. This node erases it exactly, with auto-calibration so there is nothing to tune.

Install

cd ComfyUI/custom_nodes
git clone https://github.com/lunaaispace-eng/ComfyUI-DeGrid

No dependencies beyond torch (no OpenGL/GLFW — works headless). Restart ComfyUI and search for degrid.

Quick start

1. Wire VAE Decode → VAE DeGrid → (everything else). It must sit before any sharpening, deconvolution, or upscaling — those amplify the grid, so remove it first.

2. Leave the defaults. auto mode measures each image and calibrates itself.

3. Run once. The node displays a status line, e.g.:

   grid ≈ 2.10/255 — removed (limit 0.019 auto) · edges protected: 1.2%
   

   That readout is your confirmation it worked — you don't need to pixel-peep.

Settings

| Widget | Default | What it does | |---|---|---| | enabled | on | Off = the image passes through completely untouched. Flip it for a quick A/B comparison. | | mode | auto | auto (recommended): measures the grid strength per image and sets the removal limit itself — nothing to tune, adapts to different VAEs and content. manual: uses the limit widget instead. Only switch if auto visibly under- or over-corrects. | | limit | 0.02 | Manual mode only (ignored in auto). Maximum per-pixel correction on the 0–1 scale. The VAE grid is usually 0.005–0.02. Too low → grid partially survives in contrasty areas. Too high → fine 2–3px texture (skin pores, fabric weave) gets slightly softened. | | grid_gain | 10 | Brightness amplification of the removed_grid preview only — never affects the cleaned image. Raise it if the preview looks like flat gray. | | grid_view | 4x zoom | Framing of the removed_grid preview. full frame shows the whole image (reads as gray noise at preview size — see below). 4x zoom / 8x zoom show a magnified center crop where the actual 2px lattice is visible. Preview only; the cleaned image is never cropped. |

Status line

After each run the node shows what it measured:

• grid ≈ X/255 — the estimated artifact amplitude. The raw Qwen-VAE grid is typically 1–5/255. Below ~0.5/255 the node reports the image as already clean (the filter then changes almost nothing — that's correct).
• limit N (auto|manual) — the correction cap that was applied.
• edges protected: N% — percentage of pixels where the correction hit the cap. Those are real edges/detail being passed through unsoftened. A few percent is normal; a very high number means lots of legitimate high-frequency content (or a manual limit set too low).

Reading the removed_grid preview

"It's just gray noise — is it even doing anything?" Yes. That is exactly what success looks like, and here is why: the artifact is a 2-pixel pattern. A node preview shows a 1728px image at a few hundred pixels wide, so a 2px lattice is far below what the thumbnail can render — it aliases into uniform gray "noise". The information is real; the zoom level just can't show it.

Two ways to actually see it:

• Set grid_view to 4x zoom or 8x zoom (default is 4x): the preview becomes a magnified center crop and the regular lattice pattern is plainly visible.
• Or open the preview image at 100%+ zoom.

What to look for:

| removed_grid shows | Meaning | |---|---| | Uniform fine grid / speckle, brighter over textured areas | Working correctly | | Nearly flat gray | Little or no grid in this image (check the status line — likely negligible) | | Recognizable faces, fabric, edges | Limit too high — switch to manual and lower limit |

A faint silhouette of the subject is normal (the artifact is slightly stronger over detailed areas). Recognizable detail is not.

Troubleshooting

| Symptom | Fix | |---|---| | Grid still visible in contrasty areas after filtering | mode: manual, raise limit toward 0.03–0.04 | | Fine texture (pores, weave) looks softened | mode: manual, lower limit toward 0.01 | | Status says negligible but you see a grid | The grid may be coming from a later node (sharpener, upscaler) — this node only fixes what the VAE decode produced. Check the chain order. | | removed_grid looks like flat gray | Raise grid_gain, or the image simply has no grid |

How it works

A separable Nyquist notch: 9-tap alternating-sign binomial kernel (1D response sin⁸(ω/2)), combined as center − Bx − By + Bxy, which factors into (1 − sin⁸(ωx/2))(1 − sin⁸(ωy/2)). That is an exact zero for any 2px-period pattern — vertical stripes, horizontal stripes, or checkerboard — and exact unity at DC with an 8th-order flat zero, so gradients pass through without banding.

The correction is then amplitude-clamped before subtraction, so strong real edges and legitimate fine texture pass through unsoftened — only the low-amplitude artifact band is removed. In auto mode the clamp limit is estimated per image from a robust percentile of the extracted grid component, so it adapts to different VAEs, LoRA stacks, and content automatically.

Based on the GLSL notch-filter approach shared by u/Haiku-575 on r/StableDiffusion, reimplemented in pure PyTorch with a narrower 9-tap kernel, amplitude limiting, and per-image auto-calibration.

License

Apache-2.0