Develop Reference

Saving grayscale image to a directory in python

I have a piece of code that takes in image data as grayscale values, and then converts into an image using matplotlib below
import matplotlib.pyplot as plt
import numpy
image_data = image_result.GetNDArray()
numpy.savetxt('data.cvs', image_data)
# Draws an image on the current figure
image = plt.imshow(image_data, cmap='gray')
I want to be able to export this data to LabView as a .png file. So I need to save these image to a folder where LabView and display them. Is there a function with pillow or os that can do this?

plt.imsave('output.png', image)
Does this work?

If image_data is a Numpy array of shape height x width with dtype=np.uint8 or dtype=np.uint16, you can make a PIL Image and save it as a PNG like this:
from PIL import Image
# Make PIL Image from Numpy array
pImage = Image.fromarray(image_data)
pImage.save('forLabView.png')
You can equally use OpenCV to save a Numpy array as a PNG for LabView like this:
import cv2
# Save Numpy array as PNG
cv2.imwrite('forLabView.png', image_data)
Check what your array is with:
print(image_data.shape, image_data.dtype)

Converting PIL.Image to skimage

I have 2 modules in my project: first works with image in bytes format, second requires skimage object. I need to combine them.
I have this code:
import io
from PIL import Image
import skimage.io
area = (...)
image = Image.open(io.BytesIO(image_bytes))
image = Image.crop(area)
image = skimage.io.imread(image)
But i get this error:
How can i convert an image (object/variable) to skimage? I don't necessarily need PIL Image, this is just one way to work with bytes image, cause i need to crop my image
Thanks!

Scikit-image works with images stored as Numpy arrays - same as OpenCV and wand. So, if you have a PIL Image, you can make a Numpy array for scikit-image like this:
# Make Numpy array for scikit-image from "PIL Image"
na = np.array(YourPILImage)
Just in case you want to go the other way, and make a PIL Image from a Numpy array, you can do:
# Make "PIL Image" from Numpy array
pi = Image.fromarray(na)

Creating an RGB picture in Python with OpenCV from a randomized array

I want to create a RGB image made from a random array of pixel values in Python with OpenCV/Numpy setup.
I'm able to create a Gray image - which looks amazingly live; with this code:
import numpy as np
import cv2
pic_array=np.random.randint(255, size=(900,800))
pic_array_8bit=slika_array.astype(np.uint8)
pic_g=cv2.imwrite("pic-from-random-array.png", pic_array_8bit)
But I want to make it in color as well. I've tried converting with cv2.cvtColor() but it couldnt work.
The issue might be in an array definition or a missed step. Couldn't find a similar situation... Any help how to make a random RGB image in color, would be great.
thanks!

RGB image is composed of three grayscale images. You can make three grayscale images like
rgb = np.random.randint(255, size=(900,800,3),dtype=np.uint8)
cv2.imshow('RGB',rgb)
cv2.waitKey(0)

First, you should define a random image data consisting of 3 channels using numpy as shown below-
import numpy as np
data = np.random.randint(0, 255, size=(900, 800, 3), dtype=np.uint8)
Now use, python imaging library as shown below-
from PIL import Image
img = Image.fromarray(data, 'RGB')
img.show()
You can also save the image easily using save function
img.save('image.png')

m is not a numpy array, neither a scalar

import cv2
import numpy as np
from PIL import Image
img = Image.open("test.jpg")
imgfilename = img.filename
imgb,imgg,imgr = cv2.split(img)
count = 0
I've been getting the following error when I try to run my code - this is the error I'm getting:
File "WB.py", line 9, in <module>
imgb,imgg,imgr = cv2.split(img)
TypeError: m is not a numpy array, neither a scalar

You're generally not supposed to use PIL together with numpy, these libraries don't interact a lot.
From numpy (and opencv)'s point of view, images are just 2D or 3D arrays of any given type (2D for grayscale, 3D for color). Also cv2 uses BGR by default...
Start with cv2.imread(path, cv2.IMREAD_COLOR) instead of Image.open(path).

You should use the split function available in PIL for this purpose.
Image.split()
This is because images are interpreted differently in OpenCV and PIL. Hence you cannot you the functions available in these packages interchangeably.

How to open a CR2 file in python OpenCV

I've managed to come very far on a program I'm writing. I don't know how to load CR2 files into an OpenCV Image. I've tried the following:
raw = rawpy.imread(sys.argv[1])
rgb = raw.postprocess()
PILrgb = scipy.misc.toimage(rgb)
image = cv2.imdecode(PILrgb, 1)
It was an attempt at converting the numpyarray returned by Postprocess the currently loaded RAW image and return the new resulting image as numpy array. Then calling spicy.misc.toimage to Takes a numpy array and returns a PIL image..
I get the following msg though TypeError: buf is not a numpy array, neither a scalar

It may be easier if you only rawpy
import rawpy
import cv2
raw = rawpy.imread(sys.argv[1]) # access to the RAW image
rgb = raw.postprocess() # a numpy RGB array
image = cv2.cvtColor(rgb, cv2.COLOR_RGB2BGR) # the OpenCV image