Reading and displaying multiple images in opencv

Question

I'm using this code with python and opencv for displaying about 100 images. But imshow function throws an error.

Here is my code:

nn=[]
for j in range (187) :
    nn.append(j+63)

images =[]
for i in nn:
    path = "02291G0AR\\"
    n1=cv2.imread(path +"Bi000{}".format(i))
    images.append(n1)

cv2.imshow(images)

And here is the error:

imshow() missing required argument 'mat' (pos 2)

imshow() can display only one image - to display many images you have to use imshow() many times OR you can concatenate all images into one image and then display it. But it would be big image so you would have to resize it to make it smaller. — furas
– furas, Commented Dec 12, 2019 at 10:23
Think twice about loading large numbers of images into lists unnecessarily - they take lots of memory! Maybe you can just hold their names in a list and load them one at a time to display them.... — Mark Setchell
– Mark Setchell, Commented Dec 12, 2019 at 10:23

ndrplz · Accepted Answer · 2019-12-12 10:19:03Z

2

You have to visualize one image at a time, while you are passing images which is a list
cv2.imshow() takes as first argument the name of the window

So you should iterate on your loaded images like:

for image in images:
    cv2.imshow('Image', image)
    cv2.waitKey(0)  # Wait for user interaction

You may want to take a look to the python opencv documentation about displaying images here.

answered Dec 12, 2019 at 10:19

ndrplz

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Mano · Accepted Answer · 2019-12-12 10:32:36Z

2

You can use the following snippet to montage more than one image:

from imutils import build_montages
im_shape = (129,196)
montage_shape = (7,3)
montages = build_montages(images, im_shape, montage_shape)

im_shape : A tuple containing the width and height of each image in the montage. Here we indicate that all images in the montage will be resized to 129 x 196. Resizing every image in the montage to a fixed size is a requirement so we can properly allocate memory in the resulting NumPy array. Note: Empty space in the montage will be filled with black pixels.

montage_shape : A second tuple, this one specifying the number of columns and rows in the montage. Here we indicate that our montage will have 7 columns (7 images wide) and 3 rows (3 images tall).

edited Dec 12, 2019 at 10:32

answered Dec 12, 2019 at 10:24

Mano

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