convert image from CV_64F to CV_8U

Question

I want to convert an image of type CV_64FC1 to CV_8UC1 in Python using OpenCV.

In C++, using convertTo function, we can easily convert image type using following code snippet:

image.convertTo(image, CV_8UC1);

I have searched on Internet but unable to find any solution without errors. Any function in Python OpenCV to convert this?

Answer 1

You can convert it to a Numpy array.

import numpy as np

# Convert source image to unsigned 8 bit integer Numpy array
arr = np.uint8(image)

# Width and height
h, w = arr.shape

It seems OpenCV Python APIs accept Numpy arrays as well. I've not tested it though. Please test it and let me know the result.

Answer 2

I faced similar issue and when I trying to convert the image 64F to CV_U8 I would end up with a black screen.

This link will help you understand the datatypes and conversion. Below is the code that worked for me.

from skimage import img_as_ubyte
cv_image = img_as_ubyte(any_skimage_image)

Answer 3

For those getting a black screen or lots of noise, you'll want to normalize your image first before converting to 8-bit. This is done with numpy directly as OpenCV uses numpy arrays for its images.

Before normalization, the image's range is from 4267.0 to -4407.0 in my case. Now to normalize:

# img is a numpy array/cv2 image
img = img - img.min() # Now between 0 and 8674
img = img / img.max() * 255

Now that the image is between 0 and 255, we can convert to a 8-bit integer.

new_img = np.uint8(img)

This can also be done by img.astype(np.uint8) .