Table of Contents

1  Blurring a part of an image in Python
1.1  Blur all the image
1.2  Blur only an area of the image
1.3  Conclusion

Blurring a part of an image in Python

This very short notebook shows how to open an image (eg a PNG image), and nicely blur a part of it.

In [1]:
import numpy as np
import skimage
In [2]:
%load_ext watermark
%watermark -v -m -a "Lilian Besson (Naereen)" -p numpy,skimage -g

Lilian Besson (Naereen) 

CPython 3.6.3
IPython 6.2.1

numpy 1.14.0
skimage 0.13.1

compiler   : GCC 7.2.0
system     : Linux
release    : 4.13.0-25-generic
machine    : x86_64
processor  : x86_64
CPU cores  : 4
interpreter: 64bit
Git hash   : 334c698a8a98e845aad210b3a434b0e346ecb551

Blur all the image

Let's import one of the example image, and blur all of it using skimage.filters.gaussian.

In [9]:
from skimage import data, io, filters

image = data.astronaut()
In [10]:
def imshow(image):
    io.imshow(image)
    io.show()
In [11]:
imshow(image)

/usr/local/lib/python3.6/dist-packages/skimage/io/_plugins/matplotlib_plugin.py:51: FutureWarning: Conversion of the second argument of issubdtype from `float` to `np.floating` is deprecated. In future, it will be treated as `np.float64 == np.dtype(float).type`.
  out_of_range_float = (np.issubdtype(image.dtype, np.float) and
In [5]:
from skimage.filters import gaussian
In [12]:
filtered_img = gaussian(image, sigma=1, multichannel=True)
imshow(filtered_img)

/usr/local/lib/python3.6/dist-packages/skimage/io/_plugins/matplotlib_plugin.py:51: FutureWarning: Conversion of the second argument of issubdtype from `float` to `np.floating` is deprecated. In future, it will be treated as `np.float64 == np.dtype(float).type`.
  out_of_range_float = (np.issubdtype(image.dtype, np.float) and
In [13]:
filtered_img = gaussian(image, sigma=2, multichannel=True)
imshow(filtered_img)

/usr/local/lib/python3.6/dist-packages/skimage/io/_plugins/matplotlib_plugin.py:51: FutureWarning: Conversion of the second argument of issubdtype from `float` to `np.floating` is deprecated. In future, it will be treated as `np.float64 == np.dtype(float).type`.
  out_of_range_float = (np.issubdtype(image.dtype, np.float) and

Blur only an area of the image

In [17]:
image.shape
Out[17]:
(512, 512, 3)
In [71]:
def blur(image, x0, x1, y0, y1, sigma=1, imshowall=False):
    x0, x1 = min(x0, x1), max(x0, x1)
    y0, y1 = min(y0, y1), max(y0, y1)
    im = image.copy()
    sub_im = im[x0:x1,y0:y1].copy()
    if imshowall: imshow(sub_im)
    blur_sub_im = gaussian(sub_im, sigma=sigma)
    if imshowall: imshow(blur_sub_im)
    blur_sub_im = np.round(255 * blur_sub_im)
    im[x0:x1,y0:y1] = blur_sub_im
    return im
In [72]:
filtered_img = blur(image, 80, 180, 170, 270, sigma=1)
imshow(filtered_img)

/usr/local/lib/python3.6/dist-packages/skimage/filters/_gaussian.py:108: RuntimeWarning: Images with dimensions (M, N, 3) are interpreted as 2D+RGB by default. Use `multichannel=False` to interpret as 3D image with last dimension of length 3.
  warn(RuntimeWarning(msg))
/usr/local/lib/python3.6/dist-packages/skimage/io/_plugins/matplotlib_plugin.py:51: FutureWarning: Conversion of the second argument of issubdtype from `float` to `np.floating` is deprecated. In future, it will be treated as `np.float64 == np.dtype(float).type`.
  out_of_range_float = (np.issubdtype(image.dtype, np.float) and
In [76]:
filtered_img = blur(image, 80, 180, 170, 270, sigma=5)
imshow(filtered_img)

/usr/local/lib/python3.6/dist-packages/skimage/filters/_gaussian.py:108: RuntimeWarning: Images with dimensions (M, N, 3) are interpreted as 2D+RGB by default. Use `multichannel=False` to interpret as 3D image with last dimension of length 3.
  warn(RuntimeWarning(msg))
/usr/local/lib/python3.6/dist-packages/skimage/io/_plugins/matplotlib_plugin.py:51: FutureWarning: Conversion of the second argument of issubdtype from `float` to `np.floating` is deprecated. In future, it will be treated as `np.float64 == np.dtype(float).type`.
  out_of_range_float = (np.issubdtype(image.dtype, np.float) and
In [73]:
filtered_img = blur(image, 80, 180, 170, 270, sigma=10)
imshow(filtered_img)

/usr/local/lib/python3.6/dist-packages/skimage/filters/_gaussian.py:108: RuntimeWarning: Images with dimensions (M, N, 3) are interpreted as 2D+RGB by default. Use `multichannel=False` to interpret as 3D image with last dimension of length 3.
  warn(RuntimeWarning(msg))
/usr/local/lib/python3.6/dist-packages/skimage/io/_plugins/matplotlib_plugin.py:51: FutureWarning: Conversion of the second argument of issubdtype from `float` to `np.floating` is deprecated. In future, it will be treated as `np.float64 == np.dtype(float).type`.
  out_of_range_float = (np.issubdtype(image.dtype, np.float) and
In [74]:
filtered_img = blur(image, 80, 180, 170, 270, sigma=20)
imshow(filtered_img)

/usr/local/lib/python3.6/dist-packages/skimage/filters/_gaussian.py:108: RuntimeWarning: Images with dimensions (M, N, 3) are interpreted as 2D+RGB by default. Use `multichannel=False` to interpret as 3D image with last dimension of length 3.
  warn(RuntimeWarning(msg))
/usr/local/lib/python3.6/dist-packages/skimage/io/_plugins/matplotlib_plugin.py:51: FutureWarning: Conversion of the second argument of issubdtype from `float` to `np.floating` is deprecated. In future, it will be treated as `np.float64 == np.dtype(float).type`.
  out_of_range_float = (np.issubdtype(image.dtype, np.float) and

Conclusion

That's it.