Skip to content

Rewrite the barcode example #17922

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Jul 17, 2020
Merged

Rewrite the barcode example #17922

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
52 changes: 30 additions & 22 deletions examples/images_contours_and_fields/barcode_demo.py
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,33 +1,40 @@
"""
============
Barcode Demo
============

This demo shows how to produce a one-dimensional image, or "bar code".
=======
Barcode
=======
This demo shows how to produce a bar code.

The figure size is calculated so that the width in pixels is a multiple of the
number of data points to prevent interpolation artifacts. Additionally, the
``Axes`` is defined to span the whole figure and all ``Axis`` are turned off.

The data itself is rendered with `~.Axes.imshow` using

- ``code.reshape(1, -1)`` to turn the data into a 2D array with one row.
- ``imshow(..., aspect='auto')`` to allow for non-square pixels.
- ``imshow(..., interpolation='nearest')`` to prevent blurred edges. This
should not happen anyway because we fine-tuned the figure width in pixels,
but just to be safe.
"""

import matplotlib.pyplot as plt
import numpy as np

# Fixing random state for reproducibility
np.random.seed(19680801)

# the bar
x = np.random.rand(500) > 0.7

barprops = dict(aspect='auto', cmap='binary', interpolation='nearest')

fig = plt.figure()

# a vertical barcode
ax1 = fig.add_axes([0.1, 0.1, 0.1, 0.8])
ax1.set_axis_off()
ax1.imshow(x.reshape((-1, 1)), **barprops)
code = np.array([
1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 1, 1,
0, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0,
1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1,
1, 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1])

# a horizontal barcode
ax2 = fig.add_axes([0.3, 0.4, 0.6, 0.2])
ax2.set_axis_off()
ax2.imshow(x.reshape((1, -1)), **barprops)
pixel_per_bar = 4
dpi = 100
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

So not sure this matters, but we save at 200 dpi now, don't we?

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Um, I don't think so. When did that happen?

We now oversample the thumbnails in the gallery (#17734). But that does not affect the images in the examples themselves. Maybe you are mixig this up?


fig = plt.figure(figsize=(len(code) * pixel_per_bar / dpi, 2), dpi=dpi)
ax = fig.add_axes([0, 0, 1, 1]) # span the whole figure
ax.set_axis_off()
ax.imshow(code.reshape(1, -1), cmap='binary', aspect='auto',
interpolation='nearest')
plt.show()

#############################################################################
Expand All @@ -43,3 +50,4 @@
import matplotlib
matplotlib.axes.Axes.imshow
matplotlib.pyplot.imshow
matplotlib.figure.Figure.add_axes