Why is My Matplotlib Savefig Producing a Blank Image?

Blank Output in Matplotlib's Savefig Method

In an attempt to save plots generated using Matplotlib, users may encounter an issue where the saved image appears blank. This article addresses this issue by examining a code snippet that attempts to save a plot with multiple subplots.

The provided code features three subplots, with one being conditional based on the availability of a variable named T0. The code sequence follows:

1. Creation of a new figure and subplots
2. Data visualization within the subplots
3. Call to plt.show to display the plot
4. Call to plt.savefig to save the plot in PNG format

However, the saved image (tesssttyyy.png) remains blank. To troubleshoot this issue, several factors need to be considered:

Impact of T0 existence:

• Verify the behavior of the code when T0 is not None. In such cases, an additional subplot may be created, potentially affecting the subplot indices.

Sequence of Function Calls:

• plt.show() creates a new figure. To ensure the correct figure is saved, it is recommended to call plt.savefig before plt.show(), or save the figure separately by fetching the current figure with plt.gcf().

Based on these considerations, here are two suggested resolutions:

Method 1:

• Call plt.savefig prior to plt.show() to save the initial figure before the new one is generated.

plt.savefig('tessstttyyy.png', dpi=100)
plt.show()
plt.draw()

Method 2:

• Save the current figure before calling plt.show() by using plt.gcf().

fig1 = plt.gcf()
plt.show()
plt.draw()
fig1.savefig('tessstttyyy.png', dpi=100)

Conclusion:

The blank image issue in Matplotlib's savefig method can be resolved by adjusting the sequence of function calls to ensure the correct figure is being saved or by handling the conditional creation of subplots based on T0's availability.

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