RHEF
The Radial Histogram Equalizing Filter. Solar images usually show a bright ball in a dark void; RHEF shows the corona that is actually there, on the disk and off the limb, with no parameters to tune.
rhef() at its defaults, nothing tuned.
SDO/AIA 171 Å, 2011-06-07, from the SunPy sample data.pip install sunkit-imageimport sunpy.map
from sunkit_image.radial import rhef
rhef(sunpy.map.Map("aia_171.fits")).peek()The paper (Solar Physics, 2025) Worked example API reference
- Works frame by frame, so movies need no dataset-wide statistics.
- Treats the disk and the off-limb corona the same way across the whole field of view.
- Optional Upsilon tone curve, a symmetric cousin of gamma correction, for finer control.
- Part of sunkit-image, SunPy's image-processing package. An IDL version is described in the paper.
Gilly & Cranmer (2025), Visualization of High Dynamic Range Solar Imagery and the Radial Histogram Equalizing Filter, Solar Physics.