w, h = template.shape[::-1] results in Value Error too many values to unpack

Question

Im on Python 2.7 (x86) ,Open CV 3.1.0, Windows 7 (x64)

Trying some simple template matching on Open CV

The image

The code

dark_elixir_sample = cv2.imread('dark_elixir_sample.png')

w, h = dark_elixir_sample.shape[::-1]

I'm trying to get w,h for further usage in my script, however the script returns the following error.

The error

ValueError: too many values to unpack

This: `[::-1]` reverses the array, you are looking for `[:-1]` — Tamas Hegedus, Jun 30 '16 at 12:26

score 6 · Accepted Answer · edited May 23 '17 at 10:32

6

Your image shape returns 3 dimensions

im.shape
>>> (24, 28, 3)

If you only want the first 2 do:

w, h = im.shape[:-1]
>>> (24, 28)

or

w, h, _ = im.shape
# w is 24, h is 28

Because otherwise, you are trying to unpack 3 values into only 2 variables, that won't work in Python hence your error. The _ is like a convention in Python for variables you don't want to use, or a "throwaway".

edited May 23 '17 at 10:32

Community

answered Jun 30 '16 at 12:24

bakkal

score 0 · Answer 2 · edited Feb 15 '19 at 14:01

0

dark_elixir_sample = cv2.imread('dark_elixir_sample.png',0)
w, h = dark_elixir_sample.shape[::-1]

edited Feb 15 '19 at 14:01

answered Feb 15 '19 at 14:00

Hemant

score 0 · Answer 3 · edited Sep 03 '20 at 00:21

0

you are doing

w, h = im.shape

what is happening-

w, h = imageHeight,imageWidth, number (3 for rgb, 2 for gray)

solution

w, h, _ = in.shape[::-1]

or convert into gray image

edited Sep 03 '20 at 00:21

Sylvain Lejamble

answered Jun 05 '19 at 10:14

keshavrockzz

3 Answers3