cv2imwrite

cv2.imwrite is a function in OpenCV's Python API that saves an image to a file on disk. It uses the filename extension to determine the encoder and output format (for example, JPEG, PNG, TIFF, or BMP). The function typically writes color images stored in BGR order, but it can also save grayscale images.

The signature is cv2.imwrite(filename, img, params=None) and it returns a boolean value indicating success. The filename is a string path to the destination file. The img argument is a NumPy array with height, width, and optional channel dimensions (HxW or HxWxC). For common formats, channels are 1 for grayscale, 3 for color, or 4 for BGRA.

The optional params parameter is a list of encoding parameters specific to the target format. For example, JPEG quality can be set with cv2.IMWRITE_JPEG_QUALITY, 90, and PNG compression can be adjusted with cv2.IMWRITE_PNG_COMPRESSION, 3. Example usage: cv2.imwrite('out.jpg', img, [cv2.IMWRITE_JPEG_QUALITY, 90]).

Return value and behavior: the function returns True if the image was written successfully and False otherwise. Failures can occur due to invalid paths, missing directories, unsupported formats, or mismatched image data types or channels. Ensure the input image is compatible with the chosen format (commonly 8-bit unsigned and appropriate channel count).

Notes: imwrite relies on the backend libraries available on the system and the file extension to select the encoder. If you need to avoid writing to disk, consider using cv2.imencode to obtain a memory buffer. See also: cv2.imencode, cv2.imwrite.