chop the top & bottom from a noisy screenshot

cropify.sh

# Figure out how big the input image is
GEO_INPUT=`identify $1 | cut -f 3 -d ' '`
X_INPUT=`echo $GEO_INPUT | cut -f 1 -d x`
Y_INPUT=`echo $GEO_INPUT | cut -f 2 -d x`

# Slice off a 2 pixel wide strip from the left side of the image
# Store as temp.jpg
convert $1 -crop 2x${Y_INPUT}+0+0 temp.jpg

# Now trim off the top of the temp.jpg. But we have to create a new image
# to do this.
convert temp.jpg -gravity South \
   -background red -splice 0x5 \
   -background green -splice 0x5 \
   temp2.jpg

convert temp2.jpg -trim +repage temp3.jpg
convert temp3.jpg -gravity South -chop 0x5 temp4.jpg
GEO_TOP=`identify temp4.jpg | cut -f 3 -d ' '`
Y_TOP=$(( $Y_INPUT - `echo $GEO_TOP | cut -f 2 -d x` ))

rm temp2.jpg temp3.jpg temp4.jpg
# Now do the same for the bottom.
convert temp.jpg -gravity North \
   -background red -splice 0x5 \
   -background green -splice 0x5 \
   temp2.jpg

convert temp2.jpg -trim +repage temp3.jpg
convert temp3.jpg -gravity North -chop 0x5 temp4.jpg
GEO_BOTTOM=`identify temp4.jpg | cut -f 3 -d ' '`
Y_BOTTOM=$(( $Y_INPUT - `echo $GEO_BOTTOM | cut -f 2 -d x` ))
rm temp2.jpg temp3.jpg temp4.jpg

rm temp.jpg

# Now crop the top and bottom from the image
convert $1 -crop ${X_INPUT}x$(( $Y_INPUT - $Y_TOP - $Y_BOTTOM ))+0+${Y_TOP} $2

and just execute it with:
./cropify.sh input.jpg output.jpg