See over the edge (of Linux)

[Ted Miller]

In dealing with some strange results of single-edge images, I wanted to see what MTFMapper thought the edge looked like, so I tracked down the --esf argument, and then wrote a short script to turn the raw-esf-values.txt into a simple graph. I was very revealing in what it showed about my problems.

In case you want to try it, here is my script.

#!/bin/bash
# plot first line of an edge file, as provided in single-edge mode
# $1 name of raw_esf_values.txt file 
head -n1 "$1" |tr " " "\n" > tempdata.txt
gnuplot -p -e  "set xrange [0:256] ;plot 'tempdata.txt' with line"
rm tempdata.txt

You just copy this to a text file. I called mine plot_edge.sh. To plot a certain edge file, I just type from the command line:

./plot_edge.sh <file name>

and you get a display that looks something like the one I attached (or maybe it doesn't).

If you have a better way to view edges, tell us about it.

[Frans van den Bergh]

Hi Ted,

That script looks good to me. The ESF, maybe not so much :)

You could potentially smooth out those oscillations by using --esf-model loess, or if you are certain that your edge does not have any undershoot/overshoot (should not happen to raw images, only sharpened ones), you can try the as-of-yet-undocumented --monotonic-esf-filter flag.

But both of those options are likely to be like sticking band-aids to an axe wound. Was this edge perhaps extracted from a raw, un-demosaiced image?

Regards,
Frans

[Ted Miller]

It was an unmosaiced image. This one wasn't the one that made me look for the problems, but I will keep in mind that unmosaiced images are likely to have ripples in them.