Editing Guide to madagascar programs (section)

==sffkamo==
{| class="wikitable" align="center" cellspacing="0" border="1"
! colspan="4" style="background:#ffdead;" | Computes Azimuth Move-Out (AMO) operator in the f-k log-stretch domain 
|-
! colspan="4" | sffkamo < in.rsf > out.rsf h1= h2= f1= f2= maxe=10.
|-
| ''float  '' || '''f1=''' ||   || 	input azimuth in degrees
|-
| ''float  '' || '''f2=''' ||   || 	output azimuth in degrees
|-
| ''float  '' || '''h1=''' ||   || 	input offset
|-
| ''float  '' || '''h2=''' ||   || 	output offset
|-
| ''float  '' || '''maxe=10.''' ||   || 	stability constraint
|}
Sample workflow from [http://www.ahay.org/RSF/book/sep/fkamo/paper_html/ SEP-110, 63-70 (2001)], with the addition of a bandpass for the input:

Create input -- a (t,x,y) common-offset cube:
<syntaxhighlight lang="bash">
sfspike \
n1=128 o1=0.4 d1=0.0032 k1=65 label1=t \
n2=256 o2=-1.536 d2=0.012 k2=129 label2=x \
n3=128 o3=-1.024 d3=0.016 k3=65 label3=y | \
sfbandpass flo=5 fhi=60 > spikebps.rsf
</syntaxhighlight>

Apply log-stretch FFT:
<syntaxhighlight lang="bash">
<spikebps.rsf sfstretch rule=L dens=4 |\
sffft1 |\
sffft3 axis=2 |\
sffft3 axis=3 > spikefft3.rsf
</syntaxhighlight>

Compute the AMO operator for a file of the dimensions of <tt>spikefft3.rsf</tt>. The only information taken from stdin are the n, o, d parameters:
<syntaxhighlight lang="bash">
<spikefft3.rsf sffkamo h2=2 f2=10 h1=1.8 f1=30 >oper.rsf
</syntaxhighlight>

Apply the operator by multiplication and fft back to (t, mx, my):
<syntaxhighlight lang="bash">
< spikefft3.rsf sfadd mode=prod oper.rsf |\
sffft3 axis=3 inv=y |\
sffft3 axis=2 inv=y |\
sffft1 inv=y |\
sfstretch rule=L dens=4 inv=y > spikeamo.rsf
</syntaxhighlight>

Prepare for 8-bit greyscale visualization:
<syntaxhighlight lang="bash">
< spikeamo.rsf sfbyte pclip=100 gainpanel=a > spikebyte.rsf
</syntaxhighlight>

Picture from the middle of the impulse response:
<syntaxhighlight lang="bash">
<spikebyte.rsf sfgrey3 frame1=65 frame2=129 frame3=65 \
point1=0.333 title='AMO saddle, no f-k filter' | sfpen &
</syntaxhighlight>

Picture illustrating the artifacts (i.e. need for f-k filter):
<syntaxhighlight lang="bash">
< spikebyte.rsf sfgrey3 frame1=65 frame2=97 frame3=97 \
point1=0.333 title='No f-k filter' | sfpen &
</syntaxhighlight>

Apply the f-k filter and (in this case) visualize:
<syntaxhighlight lang="bash">
< spikeamo.rsf sffft1 |\
sffft3 axis=2 |\
sffft3 axis=3 |\
sfdipfilter v1=-2.5 v2=-1.5 v3=1.5 v4=2.5 taper=2 pass=0 dim=3 |\
sffft3 axis=3 inv=y |\
sffft3 axis=2 inv=y |\
sffft1 inv=y |\
sfbyte pclip=100 gainpanel=a |\
sfgrey3 frame1=65 frame2=97 frame3=97 point1=0.333 title='With f-k filter' |\
sfpen &
</syntaxhighlight>