Convert image from PIL to openCV format

I’m trying to convert image from PIL to OpenCV format. I’m using OpenCV 2.4.3.
here is what I’ve attempted till now.

>>> from PIL import Image
>>> import cv2 as cv
>>> pimg = Image.open('D:\traffic.jpg')                           #PIL Image
>>> cimg = cv.cv.CreateImageHeader(pimg.size,cv.IPL_DEPTH_8U,3)    #CV Image
>>> cv.cv.SetData(cimg,pimg.tostring())
>>> cv.cv.NamedWindow('cimg')
>>> cv.cv.ShowImage('cimg',cimg)
>>> cv.cv.WaitKey()

But I think the image is not getting converted to CV format. The Window shows me a large brown image.
Where am I going wrong in Converting image from PIL to CV format?

Also , why do i need to type cv.cv to access functions?

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

use this:

pil_image = PIL.Image.open('Image.jpg').convert('RGB') 
open_cv_image = numpy.array(pil_image) 
# Convert RGB to BGR 
open_cv_image = open_cv_image[:, :, ::-1].copy()

Method 2

This is the shortest version I could find,saving/hiding an extra conversion:

pil_image = PIL.Image.open('image.jpg')
opencvImage = cv2.cvtColor(numpy.array(pil_image), cv2.COLOR_RGB2BGR)

If reading a file from a URL:

import cStringIO
import urllib
file = cStringIO.StringIO(urllib.urlopen(r'http://stackoverflow.com/a_nice_image.jpg').read())
pil_image = PIL.Image.open(file)
opencvImage = cv2.cvtColor(numpy.array(pil_image), cv2.COLOR_RGB2BGR)

Method 3

The code commented works as well, just choose which do you prefer

import numpy as np
from PIL import Image


def convert_from_cv2_to_image(img: np.ndarray) -> Image:
    # return Image.fromarray(cv2.cvtColor(img, cv2.COLOR_BGR2RGB))
    return Image.fromarray(img)


def convert_from_image_to_cv2(img: Image) -> np.ndarray:
    # return cv2.cvtColor(numpy.array(img), cv2.COLOR_RGB2BGR)
    return np.asarray(img)

Method 4

Here are two functions to convert image between PIL and OpenCV:

def toImgOpenCV(imgPIL): # Conver imgPIL to imgOpenCV
    i = np.array(imgPIL) # After mapping from PIL to numpy : [R,G,B,A]
                         # numpy Image Channel system: [B,G,R,A]
    red = i[:,:,0].copy(); i[:,:,0] = i[:,:,2].copy(); i[:,:,2] = red;
    return i; 

def toImgPIL(imgOpenCV): return Image.fromarray(cv2.cvtColor(imgOpenCV, cv2.COLOR_BGR2RGB));

Convert from OpenCV img to PIL img will lost transparent channel. While convert PIL img to OpenCV img will able to keep transparent channel, although cv2.imshow not display it but save as png will gave result normally.

• You can call cv2.imwrite(“./”+”fileName.png”, img); to export and check the transparent result of OpenCV img.
• Or toImgPIL(img).save(‘test.png’, ‘PNG’) to check PIL img.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0