Convert colour image into grayscale
image_ret= cv_rgb2gray_image(image)
Image that is to be converted into grayscale
Image is read from the path and returned to output variable "image_ret"
Convert the RGB image into grayscale
Image is provided by user, then the image is converted into grayscale and grayscale image is returned to the user via output variable. Converting rgb image into grayscale using this function preserves depth of the image.