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Module: novice

skimage.novice

A special Python image submodule for beginners.

Description

skimage.novice provides a simple image manipulation interface for beginners. It allows for easy loading, manipulating, and saving of image files.

This module is primarily intended for teaching and differs significantly from the normal, array-oriented image functions used by scikit-image.

Note

This module uses the Cartesian coordinate system, where the origin is at the lower-left corner instead of the upper-right and the order is x, y instead of row, column.

Examples

We can create a Picture object open opening an image file:

>>> from skimage import novice
>>> from skimage import data
>>> picture = novice.open(data.data_dir + '/chelsea.png')

We can display pictures (after running this command, close the window to access the prompt again):

>>> picture.show()  

Pictures know their format:

>>> picture.format
'png'

… and where they came from:

>>> picture.path.endswith('chelsea.png')
True

… and their size:

>>> picture.size
(451, 300)
>>> picture.width
451

As a reminder, we can preview the picture with our earlier command:

>>> picture.show()  

Changing size resizes the picture.

>>> picture.size = (45, 30)

We can preview the changes we made to the picture with the compare command:

>>> picture.compare()  

You can iterate over pixels, which have RGB values between 0 and 255, and know their location in the picture.

>>> for pixel in picture:
...     if (pixel.red > 128) and (pixel.x < picture.width):
...         pixel.red = pixel.red / 2

Pictures know if they’ve been modified from the original file

>>> picture.modified
True
>>> print(picture.path)
None

Pictures can be indexed like arrays

>>> picture[0:20, 0:20] = (0, 0, 0)

Saving the picture updates the path attribute, format, and modified state.

>>> picture.save('save-demo.jpg')
>>> picture.path.endswith('save-demo.jpg')
True
>>> picture.format
'jpeg'
>>> picture.modified
False

An image can also be restored to its original state after modification:

>>> picture[0:20, 0:20] = (0, 0, 0)
>>> picture.compare()  
>>> picture.reset()
>>> picture.compare()  
skimage.novice.open(path) Return Picture object from the given image path.
skimage.novice.Picture([path, array, xy_array]) A 2-D picture made up of pixels.

open

skimage.novice.open(path)[source]

Return Picture object from the given image path.

Picture

class skimage.novice.Picture(path=None, array=None, xy_array=None)[source]

Bases: object

A 2-D picture made up of pixels.

Examples

Load an image from a file:

>>> from skimage import novice
>>> from skimage import data
>>> picture = novice.open(data.data_dir + '/chelsea.png')

Load an image from a URL (the URL must start with http(s):// or ftp(s)://):

>>> picture = novice.open('http://scikit-image.org/_static/img/logo.png')

Create a blank 100 pixel wide, 200 pixel tall white image:

>>> pic = Picture.from_size((100, 200), color=(255, 255, 255))

Use numpy to make an RGB byte array (shape is height x width x 3):

>>> import numpy as np
>>> data = np.zeros(shape=(200, 100, 3), dtype=np.uint8)
>>> data[:, :, 0] = 255  # Set red component to maximum
>>> pic = Picture(array=data)

Get the bottom-left pixel:

>>> pic[0, 0]
Pixel(red=255, green=0, blue=0, alpha=255)

Get the top row of the picture:

>>> pic[:, pic.height-1]
Picture(100 x 1)

Set the bottom-left pixel to black:

>>> pic[0, 0] = (0, 0, 0)

Set the top row to red:

>>> pic[:, pic.height-1] = (255, 0, 0)

Attributes

path The path to the picture.
array Image data stored as numpy array.
xy_array Image data stored as numpy array with origin at the bottom-left.
__init__(path=None, array=None, xy_array=None)[source]
alpha

The transparency component of the pixel (0-255).

array

Image data stored as numpy array.

blue

The blue component of the pixel (0-255).

compare()[source]

Compare the image to its unmodified version.

format

The image format of the picture.

static from_size(size, color='black')[source]

Return a Picture of the specified size and a uniform color.

Parameters:

size : tuple

Width and height of the picture in pixels.

color : tuple or str

RGB or RGBA tuple with the fill color for the picture [0-255] or a valid key in color_dict.

green

The green component of the pixel (0-255).

height

The height of the picture.

modified

True if the picture has changed.

path

The path to the picture.

red

The red component of the pixel (0-255).

reset()[source]

Reset image to its original state, removing modifications.

rgb

The RGB color components of the pixel (3 values 0-255).

rgba

The RGBA color components of the pixel (4 values 0-255).

save(path)[source]

Saves the picture to the given path.

Parameters:

path : str

Path (with file extension) where the picture is saved.

show()[source]

Display the image.

size

The size (width, height) of the picture.

width

The width of the picture.

xy_array

Image data stored as numpy array with origin at the bottom-left.