Python – OpenCv CreateImage Function isn’t working

opencvpython

I'm trying to create an image using opencv v 2.1, but I get this error:

image=cv.CreateImage((w,h),no_of_bits,channels)

AttributeError: 'module' object has no attribute 'CreateImage'

The code is

#!/usr/bin/python

import cv 
from opencv import *
from opencv.cv import *
from opencv.highgui import *
import sys

import PIL

w=500
h=500
no_of_bits=8
channels=3
image=cv.CreateImage((w,h),no_of_bits,channels) 

cv.ShowImage('WindowName',image) 
cvWaitKey()

Best Solution

Since there aren't that many good examples how to create new blank image filled with a color using cv2, here's one:

Create OpenCV image of certain (R, G, B) color:

import cv2
import numpy as np

def create_blank(width, height, rgb_color=(0, 0, 0)):
    """Create new image(numpy array) filled with certain color in RGB"""
    # Create black blank image
    image = np.zeros((height, width, 3), np.uint8)

    # Since OpenCV uses BGR, convert the color first
    color = tuple(reversed(rgb_color))
    # Fill image with color
    image[:] = color

    return image

# Create new blank 300x300 red image
width, height = 300, 300

red = (255, 0, 0)
image = create_blank(width, height, rgb_color=red)
cv2.imwrite('red.jpg', image)

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Python – Calling a function of a module by using its name (a string)

Assuming module foo with method bar:

import foo
method_to_call = getattr(foo, 'bar')
result = method_to_call()

You could shorten lines 2 and 3 to:

result = getattr(foo, 'bar')()

if that makes more sense for your use case.

You can use getattr in this fashion on class instance bound methods, module-level methods, class methods... the list goes on.

Python – Using global variables in a function

You can use a global variable within other functions by declaring it as global within each function that assigns a value to it:

globvar = 0

def set_globvar_to_one():
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def print_globvar():
    print(globvar)     # No need for global declaration to read value of globvar

set_globvar_to_one()
print_globvar()       # Prints 1

Since global variables have a long history of introducing bugs (in every programming language), Python wants to make sure that you understand the risks by forcing you to explicitly use the global keyword.

See other answers if you want to share a global variable across modules.

Best Solution

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Python – Calling a function of a module by using its name (a string)

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