procedure abba ( ipref, sp1, sp2, opref, so1 , flat, geomap )
#
# Procedure to take ABBA differences
# Richard Elston 3/6/93
#
string ipref    {prompt="input image prefix"}
int    sp1      {prompt="starting number of input image"}
int    sp2      {prompt="stopping number of input image"}
string opref    {prompt="output image prefix"}
int    so1      {prompt="starting output number"} 
string flat     {prompt="flat field image"}
string geomap   {prompt="geotran image name"}

begin
	int i
	string sa1, sa2, sb1, sb2, oname   
	string wrk1, wrk2
	string num1

	string inpref, outpref
	int p1, p2, o1

	inpref = ipref
	p1 = sp1
	p2 = sp2
	outpref = opref
	o1 = so1

	wrk1 = mktemp("xyz")
	wrk2 = mktemp("xyz")

for ( i = p1 ; i <= p2 ; i += 1) {

	if ( i < 10 ) {
		sa1 = inpref//"00"//i
	}
	else if ( i < 100 ) {
		sa1 = inpref//"0"//i
	}
	else {
		sa1 = inpref//i
	}

	i = i+1
	if ( i < 10 ) {
		sb1 = inpref//"00"//i
	}
	else if ( i < 100 ) {
		sb1 = inpref//"0"//i
	}
	else {
		sb1 = inpref//i
	}

	i = i+1

	if ( i < 10 ) {
		sb2 = inpref//"00"//i
	}
	else if ( i < 100 ) {
		sb2 = inpref//"0"//i
	}
	else {
		sb2 = inpref//i
	}

	i = i+1

	if ( i < 10 ) {
		sa2 = inpref//"00"//i
	}
	else if ( i < 100 ) {
		sa2 = inpref//"0"//i
	}
	else {
		sa2 = inpref//i
	}


	if ( o1 < 10 ) {
		oname = outpref//"00"//o1
	}
	else if ( o1 < 100 ) {
		oname = outpref//"0"//o1
	}
	else {
		oname = outpref//o1
	}

	o1=o1+1
	imarith(sa1, "+", sa2, wrk1)
	imarith(sb1, "+", sb2, wrk2)
	imarith(wrk1,"-",wrk2, wrk1)
	imarith (wrk1, "/", flat, oname) 
	hedit(oname, "DISPAXIS", "2", add+, ver-)
	transform(oname,oname,geomap)
	imdel(wrk1,ver-)
#	background(oname,wrk1)
#	imdel(oname,ver-)
#	imrename(wrk1, oname)
	display(oname, 1)

	imdel(wrk1,ver-)
	imdel(wrk2,ver-)

}

	end