procedure abba ( ipref, sp1, sp2, opref, so1 , flat )
#
# 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"}
bool   backg    {yes, prompt="Fit and remove background residual",mode="h"}
string bksamp   {"*", prompt="Sample of points to use for Background",mode="h"}
bool   bkinter  {yes, prompt="Fit background interactively",mode="h"}

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
	print("A1 = ",sa1,"    A2 = ",sa2)
	print("B1 = ",sb1,"    B2 = ",sb2)
	print( oname, " = A1+A2-B1-B2")
	imarith(sa1, "+", sa2, wrk1)
	imarith(sb1, "+", sb2, wrk2)
	imarith(wrk1,"-",wrk2, wrk1)
	imarith(wrk1,"/", 2.0, wrk1)
	xdispflatten(wrk1, flat, oname) 
	xdisplay(oname)

	if (backg) {
		
 	print ("******Fiting Residual Background*******")	
	imdel (wrk1, ver-)

background (oname//".ksub.imh",
wrk1, axis=2, interactive=bkinter, sample=bksamp, naverage=1,
function="chebyshev", order=1, low_reject=2., high_reject=2., niterate=5,
grow=0., graphics="stdgraph", cursor="")

	imdel (oname//".ksub.imh")
	imrename (wrk1, oname//".ksub.imh")

background (oname//".hsub.imh",
wrk1, axis=2, interactive=bkinter, sample=bksamp, naverage=1,
function="chebyshev", order=1, low_reject=2., high_reject=2., niterate=5,
grow=0., graphics="stdgraph", cursor="")

	imdel (oname//".hsub.imh")
	imrename (wrk1, oname//".hsub.imh")

background (oname//".jsub.imh",
wrk1, axis=2, interactive=bkinter, sample=bksamp, naverage=1,
function="chebyshev", order=1, low_reject=2., high_reject=2., niterate=5,
grow=0., graphics="stdgraph", cursor="")

	imdel (oname//".jsub.imh")
	imrename (wrk1, oname//".jsub.imh")

background (oname//".isub.imh",
wrk1, axis=2, interactive=bkinter, sample=bksamp, naverage=1,
function="chebyshev", order=1, low_reject=2., high_reject=2., niterate=5,
grow=0., graphics="stdgraph", cursor="")

	imdel (oname//".isub.imh")
	imrename (wrk1, oname//".isub.imh")
	
	xdisplay(oname)

	}

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

}

	end