System Information

• Python 3.12.2
• opencv-python-headless 4.11.0.86
• macOS ARM64 14.6.1
• mypy 1.14.1
• Numpy 2.2.2

Detailed description

The color parameter to cv2.line is overly strict. The parameter is marked as a Scalar value which is typed as Sequence[float]. However, for single channel images, the functions also accept a standard float.

Consider this program:

import cv2
import numpy as np

image = np.zeros((10, 10), dtype=np.uint8)
cv2.line(image, (1, 1), (8, 8), color=255)

With the following Mypy configuration:

[tool.mypy]
strict = true
plugins = [
    "numpy.typing.mypy_plugin",
]

Running Mypy produces an error:

$ mypy main.py
main.py:5: error: No overload variant of "line" matches argument types "ndarray[tuple[int, int], dtype[unsignedinteger[_8Bit]]]", "tuple[int, int]", "tuple[int, int]", "int"  [call-overload]
main.py:5: note: Possible overload variants:
main.py:5: note:     def line(img: Mat | ndarray[Any, dtype[integer[Any] | floating[Any]]], pt1: Sequence[int], pt2: Sequence[int], color: Sequence[float], thickness: int = ..., lineType: int = ..., shift: int = ...) -> Mat | ndarray[Any, dtype[integer[Any] | floating[Any]]]
main.py:5: note:     def line(img: UMat, pt1: Sequence[int], pt2: Sequence[int], color: Sequence[float], thickness: int = ..., lineType: int = ..., shift: int = ...) -> UMat
Found 1 error in 1 file (checked 1 source file)

But the program executes fine.

This same issue also affects floodFill's newVal parameter

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues, forum.opencv.org, Stack Overflow, etc and have not found any solution
• I updated to the latest OpenCV version and the issue is still there
• There is reproducer code and related data files (videos, images, onnx, etc)