raja@bombay.cps.msu.edu (Narayan S. Raja) (12/11/90)
Some of my images have noise stripes (i.e. periodic noise at a particular orientation, that visually looks like stripes). Is there any publicly available software that will filter out noise of a particular orientation and spatial frequency from images? (i.e. a notch filter -- the opposite of a bandpass filter, of course in the spatial frequency domain). Thanks in advance, Narayan Sriranga Raja.
raja@bombay.cps.msu.edu (Narayan S. Raja) (12/13/90)
In article <1990Dec11.031331.22486@msuinfo>, I wrote:
< Some of my images have noise stripes (i.e.
< periodic noise at a particular orientation,
< that visually looks like stripes).
Well, there weren't any good tips about
this one, but I did get some requests to
summarize the info.
I managed to solve the problem anyway, so
here goes:
1. by separating the red, blue, and green
planes I found that the red image was
very stripy, while blue and green were
absolutely clean -- must have been
something goofy about the red sensors.
2. Moreover, the stripes were fairly narrow
and in any given image, were either
vertical or horizontal.
I was able to remove the stripes with very
little loss of sharpness by convolving the
stripy (red) image plane with a small mask
tailored to average the intensities in either
horizontal or vertical directions (depending
on whether the stripes were vertical or
horizontal. In case of horizontal stripes,
average the intensities vertically, and vice
versa).
E.g., in case of vertical stripes, the mask
0.11 0.00 0.11
0.11 0.34 0.11
0.11 0.00 0.11
worked well for me. After de-striping the
red image satisfactorily, a better-quality
colour image is obtained by recombining the
r,g,b planes.
Narayan Sriranga Raja.