创建具有自定义图像比例的绘图表达图像

Question

I'm trying to build a very simple plot in plotly express with custom dimensions but cannot get the result I want.

My image is an array with dimensions 300 and 5000, I want it to be stretched into a smaller dimension, such that it looks big on a screen.

It is super easy to do in matplotlib , but I get weird results in plotly . This is what I have using matplotlib :

plt.figure(figsize=(20, 10), dpi=80)
image = np.random.random([300, 5000])
plt.imshow(image, vmin=0, vmax=1, cmap='gray_r', aspect='auto')

Answer 1

If I understand correctly, this is what you currently have:

# Missing imports
import matplotlib.pyplot as plt
import numpy as np

# Your code from the question
plt.figure(figsize=(20, 10), dpi=80)
# Smaller array to speed things up
image = np.random.random([30, 500])
plt.imshow(image, vmin=0, vmax=1, cmap="gray_r", aspect="auto")

This results in the following output:

Now you want to use plotly. You can plot the same image with the default settings:

# Plotly default
import plotly.express as px
fig = px.imshow(image)
fig.show()

Resulting in:

To get the same colour and aspect ratio you need to add some arguments to px.imshow . Note that here the width and height are in pixels, so you need to convert your (20, 10) numbers accordingly using the dpi of 80.

# Plotly to match matplotlib
fig = px.imshow(image, color_continuous_scale="gray_r", aspect="auto", width=1600, height=800)
fig.show()

This results in: