OpenCV fitEllipse_1

OpenCV fitEllipse_1 is fitEllipse_0 under a different number. Same single input (points, an NPARRAY of at least 5 2D points), same cv2.fitEllipse call, same single output: a literal (STRING) carrying the fitted ellipse as a RotatedRect - ((center_x, center_y), (width, height), angle). The duplicate is the pack's standard MatLike/UMat artifact from OpenCV's type stubs; there's no behavioral difference to weigh.

The useful content is all in the _0 article. Recap: least-squares fit of an ellipse to a point set, ideal for "describe my blob" workflows. Get your points from findNonZero off a thresholded mask (the pack's natural point-list producer), keep them as floats, and the node returns the ellipse's center, axes, and angle as a serialized value. Feed those values back into this pack's ellipse node (as a literal) to draw the fit.

What to actually watch for

• The output isn't an image. It's a composite value serialized as text. Trying to preview it throws the pack's 'NoneType' object has no attribute 'shape' error. Read it, or feed its parts into drawing nodes.
• Five points minimum, floats required. Fewer and OpenCV asserts; integers and OpenCV grumbles. np.float32 is the safe cast.
• Garbage in, confident ellipse out. The fit always produces an ellipse; it won't tell you that your point set wasn't ellipse-like. That's a you problem, not a node problem.

Install

Same pack. ComfyUI Manager → search opencv-comfyui → install → restart, or:

cd ComfyUI/custom_nodes
git clone https://github.com/geroldmeisinger/opencv-comfyui

requirements.txt installs opencv-contrib-python, numpy, torch. Startup failure almost always means cv2 didn't import - duplicate OpenCV installs are the usual suspect, and Cannot import name 'guidedFilter' is the symptom.

Use _0 or _1, doesn't matter. When you need a more outlier-robust fit, fitEllipseAMS is the sibling function worth knowing about.