how to convert an RGB image to numpy array?

I have an RGB image. I want to convert it to numpy array. I did the following

im = cv.LoadImage("abc.tiff")
a = numpy.asarray(im)

It creates an array with no shape. I assume it is a iplimage object.

Solution 1:

You can use newer OpenCV python interface (if I'm not mistaken it is available since OpenCV 2.2). It natively uses numpy arrays:

import cv2
im = cv2.imread("abc.tiff",mode='RGB')
print type(im)

result:

<type 'numpy.ndarray'>

Solution 2:

PIL (Python Imaging Library) and Numpy work well together.

I use the following functions.

from PIL import Image
import numpy as np

def load_image( infilename ) :
    img = Image.open( infilename )
    img.load()
    data = np.asarray( img, dtype="int32" )
    return data

def save_image( npdata, outfilename ) :
    img = Image.fromarray( np.asarray( np.clip(npdata,0,255), dtype="uint8"), "L" )
    img.save( outfilename )

The 'Image.fromarray' is a little ugly because I clip incoming data to [0,255], convert to bytes, then create a grayscale image. I mostly work in gray.

An RGB image would be something like:

 outimg = Image.fromarray( ycc_uint8, "RGB" )
 outimg.save( "ycc.tif" )

Solution 3:

You can also use matplotlib for this.

from matplotlib.image import imread

img = imread('abc.tiff')
print(type(img))

output: <class 'numpy.ndarray'>

Solution 4:

As of today, your best bet is to use:

img = cv2.imread(image_path)   # reads an image in the BGR format
img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)   # BGR -> RGB

You'll see img will be a numpy array of type:

<class 'numpy.ndarray'>