How to export high quality image from the plot

[changliao1025]

Hi,
Currently, I see that I can use screenshot and save_graphic to export a image. However, both functions do not provide setting for DPI. The screenshot function provides the window_size to improve the quality, though.

So my question is, whether it is possible to set DPI directly somewhere?

Thank you.

[bjlittle]

Hey @changliao1025,

Great to hear from you.

Okay, as far as I'm aware you can't control the DPI from pyvista, but as you mention you can configure the window_size.

However, you could take the following approach to hand-off the saving with the relevant controls to matplotlib from pyvista (and geovista) e.g.,

import matplotlib.pyplot as plt
import pyvista as pv

plotter = pv.Plotter(off_screen=True)
_ = plotter.add_mesh(pv.Sphere())
plotter.show()

plt.imshow(plotter.image)
plt.savefig("sphere.png", dpi=500)

The resultant sphere.png:

Is this suitable for your workflow?

[bjlittle]

Note that, within matplotlib you can then control the saved image (as normal) e.g., turn-off the axes and border etc i.e.,

import matplotlib.pyplot as plt
import pyvista as pv

plotter = pv.Plotter(off_screen=True)
_ = plotter.add_mesh(pv.Sphere())
plotter.show()

plt.imshow(plotter.image)
plt.axis("off")
plt.savefig("sphere.png", dpi=500, bbox_inches="tight", pad_inches=0)

Now gives the following sphere.png:

[changliao1025]

That seems promising! I will give a try.

[changliao1025]

The quality is still very low. I think
plt.imshow(plotter.image)
would only take the raster image, so the DPI is not actually working anymore.

[bjlittle]

@changliao1025

If you play around with the following options, you may be able to hit the quality sweetspot e.g.,

import matplotlib.pyplot as plt
import pyvista as pv

plotter = pv.Plotter(off_screen=True)

plotter.window_size = (640, 480)       #  <--- set the window size
plotter.image_scale = 10               #  <--- scale screenshot image i.e., window_size * image_scale 

_ = plotter.add_mesh(pv.Sphere())
plotter.show()

plt.imshow(plotter.image)
plt.axis("off")
plt.savefig("sphere.png", dpi=500, bbox_inches="tight", pad_inches=0)

Does this help?

[bjlittle]

For reference see:

• https://docs.pyvista.org/api/plotting/_autosummary/pyvista.plotter.screenshot
• https://docs.pyvista.org/api/plotting/_autosummary/pyvista.plotter.image_scale

[bjlittle]

This certain demonstrates resolution improvements for the resultant png that you can control e.g.,

[changliao1025]

I wonder what is the benefit of using the combination of both, or simply just using the larger window size.

[bjlittle]

@changliao1025 Hmmm not sure really ... but I'd guess that image_scale might just be a simple convenience to easily scale the image without tinkering with the an explicitly or implicitly (default) plotter window size, thus giving you the extra resolution control that you might need.

@tkoyama010 Can you explain the difference?