CODEWITHSUNDEEP
c++pythoncopencvpython-imaging-library
fang
fang

Reputation: 617

Python PIL Image.tostring('raw') and IplImage->imageData of OpenCV

As stated in documentation:

IplImage.imageData (from OpenCV library):

A pointer to the aligned image data

Image.tostring() (from Python PIL):

Returns a string containing pixel data, using the standard "raw" encoder.

What is the difference between the results of Image.tostring() and IplImage.imageData ? What should I do if I want to get exactly the same data as returned by IplImage.imageData in Python ?

EDIT: Just to clarify, I need to use PIL to load images as I have a python service to receive data from internet and there's no straightforward way in OpenCV to load an image from memory instead of disk.

Upvotes: 1

Views: 5062

Answers (2)

Andreas Bruse
Andreas Bruse

Reputation: 31

There is a straightforward way of reading images from memory in opencv.

Using cv (version 1)

import cv

# First get the compressed image data. This can be retrieved from
# a socket, a file, or whatever you want.
jpegdata = open('myimage.jpg','r').read()

# Create an opencv matrix to hold the compressed data
cvmat = cv.CreateMatHeader(1, len(jpegdata), cv.CV_8U)
cv.SetData(cvmat, jpegdata, len(jpegdata))

# Now let opencv decompress your image
cvimage = cv.DecodeImage(cvmat, cv.CV_LOAD_IMAGE_COLOR)

Using cv2 (and numpy)

import cv2
import numpy as np

# First get the compressed image data. This can be retrieved from
# a socket, a file, or whatever you want.    
jpegdata = open('myimage.jpg','r').read()

# Convert your compressed data to a numpy array
nparr = np.fromstring(jpegdata, np.uint8)

# Now use imdecode to decompress it
cvimage = cv2.imdecode(nparr, cv2.CV_LOAD_IMAGE_COLOR)

Upvotes: 3

Vinayak Kolagi
Vinayak Kolagi

Reputation: 1881

While Opencv image, pixel data is ordered as BGR, in PIL it is RGB. You can convert a PIL image data to opencv as below.

import Image, cv
pi = Image.open('building.jpg')       # PIL image
cv_im = cv.CreateImageHeader(pi.size, cv.IPL_DEPTH_8U, 3)
cv.SetData(cv_im, pi.tostring())

For more information here.

http://opencv.willowgarage.com/documentation/python/cookbook.html

Upvotes: 1

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