OpenCV line_1

Straight to it: OpenCV line_1 and OpenCV line_0 are identical. Every _0/_1 pair in this pack is the same function twice, because OpenCV declares its functions with two overloads (plain matrices and OpenCL-backed UMat) and the pack's generator numbered them instead of deduplicating. So the real question isn't "which one do I need" - it's "do I need this at all."

The answer is: when you want to draw a line on an image inside a workflow, without loading a model, this is how. It's cv2.line wrapped as a node - the primitive underneath every box overlay, ruler callout, and "look at this region" arrow in image-processing land. If you've ever wanted to mark two points on a generated frame and save the result, this is a one-node solution.

What you actually type

Because the pack parses composite types as Python-literal strings, the drawing coordinates and the color are text boxes, not nice number widgets:

• pt1 = [50, 50] - start point
• pt2 = [400, 300] - end point
• color = [0, 255, 0] - BGR, not RGB (green here; flip it to [255, 0, 0] and you get blue - one of OpenCV's most reliable footguns)

Parens work too: (50, 50). Malformed syntax gives you the pack's signature invalid syntax (<unknown>, line 0).

The remaining inputs:

• img - NPARRAY in (remember Image2Nparray/Nparrays2Image to cross between Comfy and OpenCV world).
• thickness - pixels wide; 1–2 for hairlines, higher for markers.
• lineType - 16 is anti-aliased (LINE_AA, use it), 8 is not. 4 is 4-connected.
• shift - sub-pixel bit-shift precision. 0.

One output, nparray, the image with the line drawn.

Install

Same as every node in the pack:

cd ComfyUI/custom_nodes
git clone https://github.com/geroldmeisinger/opencv-comfyui
pip install opencv-contrib-python

Restart ComfyUI. Or use ComfyUI Manager (search "opencv"). Dependencies are just opencv-contrib-python, numpy, torch - no models to fetch.

The gotchas

• Wrong color / invisible line - check BGR ordering, and make sure pt1/pt2 are within the image bounds. Drawing outside the frame isn't an error, it's just nothing.
• invalid syntax - a typo in a literal string. The error message is unhelpful; check the string boxes first.
• Batch error - Only images with batch_size==1 are supported! → ImageFromBatch with length=1 before converting.

One more honest note: the author himself said in his r/comfyui announcement that this pack isn't simpler than the big image-processing suites - "No ;)" was his literal answer when asked. It's for people who want raw, intentional cv2 access. If drawing lines is all you need, a dedicated annotation pack will give you friendlier inputs; if you're already elbow-deep in nparrays, line_1 is right there.