Unable to pass multiple images to OpenCv at once

Question

I've been reading fairly obsessively for days now, but I'm only a few weeks into learning python and openCv and I'm at a total loss with this.

I have a class function that draws rectangles around a "needle" image found on a "haystack" image. The haystack is an application window I'm capturing in real-time.

class Search:

def __init__(self, needle_img_path, method=cv.TM_CCOEFF_NORMED):
    
    # set the method used to load the image 
    self.method = method

    # load the needle image
    self.needle_img = cv.imread(needle_img_path, cv.IMREAD_UNCHANGED)

    # Save the dimensions of the needle image
    self.needle_w = self.needle_img.shape[1]
    self.needle_h = self.needle_img.shape[0]

This is how I'm passing a single image into the above function.

# the window to capture 
wincap = WindowCapture('X')

# set the needle image
images = x.jpg

# perform the search 
search = Search(images)

When I try passing more images in directly images = ("x.jpg","y.jpg")

I get the error:

   self.needle_img = cv.imread(needle_img_path, cv.IMREAD_UNCHANGED)
TypeError: Can't convert object of type 'tuple' to 'str' for 'filename'

And when I try storing the the images in an array images = [cv.imread(file) for file in glob.glob('localpath')]

I get the error:

    self.needle_img = cv.imread(needle_img_path, cv.IMREAD_UNCHANGED)
TypeError: Can't convert object of type 'list' to 'str' for 'filename'

When I place print(images) below a single successfully loaded image images = x.jpg it returns x.jpg so I think it's expecting a string and not an array but I'm not sure how to do that.

Answer 1

If your argument is passed as a tuple, you'll need to iterate over the list of image paths. If it's passed as a string, you'll want to pass that directly to the imread call.

Consider making the following modification:

import cv2 as cv

class Search:
    def __init__(self, needle_img_path, method=cv.TM_CCOEFF_NORMED):
        # set the method used to load the image
        self.method = method
        self.needle_imgs = []

        # load the needle image
        if type(needle_img_path) is str:
            self.needle_imgs.append(cv.imread(needle_img_path, cv.IMREAD_UNCHANGED))
        elif type(needle_img_path) is list or tuple:
            for img in needle_img_path:
                self.needle_imgs.append(cv.imread(img, cv.IMREAD_UNCHANGED))

    def do_something_with_images(self):
        for img in self.needle_imgs:
            print(img.shape)

# set the needle image
images = ("C:\\Test\\x.jpg", "C:\\Test\\y.jpg")

# perform the search
search = Search(images)

# Do something to each individual image
search.do_something_with_images()