  Images of the extended solar corona, as observed by white-light coronagraphs
as observed by different white-light coronagraphs include the K- and F-corona
and suffer from a radial variation in intensity. These images require
separation of the two coronal components with some additional image-processing
to reduce the intensity gradient and analyse the structures and processes
occurring at different heights in the solar corona within the full field of
view. To process these bulk coronagraph images with steep radial-intensity
gradients, we have developed an algorithm: Simple Radial Gradient Filter
(SiRGraF). This algorithm is based on subtracting a minimum background
(F-corona) created using long-duration images and then dividing the resultant
by a uniform intensity gradient image to enhance the K-corona. We demonstrate
the utility of this algorithm to bring out the short time-scale transient
structures of the corona. SiRGraF could be used to reveal and analyse such
structures. It is not suitable for quantitative estimations based on intensity.
We have successfully tested the algorithm on images of the LASCO-C2 onboard the
Solar and Heliospheric Observatory (SOHO), and COR-2A onboard the STEREO with
good signal to noise ratio (SNR) along with low-SNR images of STEREO/COR-1A and
the KCoronagraph. We also compared the performance of SiRGraF with Normalising
Radial Gradient Filter (NRGF). We found that when hundreds of images have to be
processed, SiRGraF works faster than NRGF, providing similar brightness and
contrast in the images and separating the transient features. Moreover, SiRGraF
works better on low-SNR images of COR-1A than NRGF, providing better
identification of dynamic coronal structures throughout the field of view. We
discuss the advantages and limitations of the algorithm.
