cv2cvtColor

cv2.cvtColor is a function in OpenCV’s Python interface used to convert an image from one color space to another. It takes two required arguments: src, the input image as a NumPy array, and code, a conversion flag that specifies the source and destination color spaces. The function returns a new image in the target color space. The conversion flag is one of many COLOR_* constants, such as COLOR_BGR2GRAY, COLOR_BGR2RGB, COLOR_BGR2HSV, COLOR_RGB2Lab, COLOR_YCrCb2BGR, and so on. OpenCV uses BGR ordering by default for color images in Python, not RGB, so many conversions start from BGR.

Common tasks include converting to grayscale for thresholding or feature detection, converting to HSV for color filtering, or converting between RGB and BGR for compatibility with other libraries. The function is central to many preprocessing and feature extraction pipelines in computer vision.

Input compatibility and behavior: cv2.cvtColor supports a range of image depths, typically 8-bit, and may handle other depths depending on the conversion. If an unsupported conversion code is provided for the input type, OpenCV raises an error. The operation is implemented in optimized native code, making it efficient for routine image processing.

Example: gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) to convert a color image to grayscale for subsequent processing.