color-correction

Color Correction (measure, don't eyeball)

The core principle

You cannot reliably judge color from a storyboard / contact sheet. "Is it washed out?" flip-flops by eye, especially on AI-gen video. Make color measurable with the analyze_color MCP tool, read the numbers like a colorist reads scopes, then pick the fix the data points to — and re-measure to confirm. The whole skill is this loop:

extract a frame ─► analyze_color ─► read black/white points + contrast + saturation
       ▲                                          │
       │                                          ▼
   re-measure  ◄──── apply fix (levels / contrast / match) ◄── diagnose from the numbers

Origin: on a WAN-Animate render we argued for many turns over whether the clip was "washed out." The instant we measured it, the answer was unambiguous and the correct fix (a contrast stretch, NOT the color-match nodes we'd been adding) fell straight out.

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The analyze_color tool

Read-only. Source = asset_id, a ComfyUI output ref (filename/subfolder/type), or an image path (absolute, or under the output dir). It returns per-image stats + heuristic flags + a one-line verdict, and (optional) an overlaid R/G/B/luma histogram PNG.

analyze_color({ filename: "render_00007_.png" })                 # absolute numbers
analyze_color({ path: "frame.png", reference_path: "src.jpg" })  # + shot-match deltas
analyze_color({ filename: "x.png", histogram: true })            # + histogram image

Videos: analyze_color is image-only (no ffmpeg dep). Extract a frame first with the ComfyUI venv's cv2:

"<comfy-venv>/python" -c "import cv2; c=cv2.VideoCapture(r'IN.mp4'); n=int(c.get(7)); \
  c.set(1, n//2); _,f=c.read(); cv2.imwrite(r'frame.png', f)"

(grab the middle frame, or frame 0; for window-drift checks grab a frame from each window.)

What the numbers mean (8-bit)

Field	Reads like a scope	Healthy-ish
luma.blackPoint (1st pct)	where shadows bottom out	~0–16 (lifted if >16)
luma.whitePoint (99th pct)	where highlights top out	~240–255 (dim if <235)
luma.contrast (std)	overall punch	~45+ (flat if <45)
luma.dynamicRange	white−black	wide is good
saturation.meanSaturation (HSV S)	vectorscope spread	~0.25+ (dull if <0.22)
channels.{r,g,b}Mean + castHint	RGB parade / white balance	spread <~12 = neutral
luma.clippedHighPct/LowPct	blown / crushed pixels	keep low (<~2%)