C	PROGRAM BFOLLOW.FT
C	----------------
C
C
C
C	###SUBROUTINE BFOLLOW(JX,JY,IOPR)
C
C	PETER LEMKIN
C	IMAGE PROCESSING UNIT, DCBD
C	NATIONAL CANCER INSTITUTE
C	NATIONAL INSTITUTES OF HEALTH
C	9000 ROCKVILLE PIKE
C	BETHESDA, MD. 20014
C
C	NOV 15, 1977
C	NOV 14, 1977
C	NOV 11, 1977
C	JUNE 10, 1977
C	MAY 14, 1977
C	MAY 13, 1977
C	MARCH 28, 1977
C	MARCH 17, 1977
C	FEB 26, 1977
C	NOV 15, 1976
C	NOV 10, 1976
C	NOV 4, 1976
C
C	PURPOSE
C	-------
C	BFOLLOW FOLLOWSTHE CURVE SPECIFIED BY (IX,IY) WHEN IT
C	IS INITIALIZED BY OPR #1,#2. SUCCESSIVE CALLS RETURN
C	NEW CURVE POINTS UNTIL THE INITIAL POINT IS LOCATED
C	IN WHICH CASE (-1,TRUE PERIMETER) IS RETURNED IN (IX,IY).
C
C	NOTE: (MEM,IBYTE,IX,IY,IZ) IN COMMON ARE SAVED
C	ON ENTRY AND RESTORED ON THE RETURN.
C
C	IOPR	FUNCTION
C	----	--------
C	1	DEFINE THE BM (MEM,IBYTE) TO SEARCH FROM (JX,JY).
C
C	2	DEFINE THE CONNECTED COMPONENT COLOR TO SEARCH FOR
C		IN JX.
C
C	3	START NEW BOUNDARY FOLLOWING STARTING AT
C		POINT (IX,IY) ==>(IXFIRST,IYFIRST).
C
C	4	GET NEXT (IX,IY) POINT ON BOUNDARY. RETURN
C		(IX,IY) IF VALID NEXT POINT, CHAIN CODE DIRECTION ==>MQ
C		(-1,TRUE PERIMETER) IF REACHED THE INITIAL (IXFIRST,IYFIRST),
C		(-2,0) IF ISOLATED PIXEL,
C		(-3,0) IF COMPONENT GOT LOST.
C	OPDEFS
C	------
S	OPDEF	TADI	1400
S	OPDEF	DCAI	3400
C
C
S	OPDEF	DISP1	6435
S	OPDEF	DISP2	6436
C
C
S	OPDEF	MUY	7405
S	OPDEF	DVI	7407
C
S	OPDEF	MQA	7501
S	OPDEF	MQL	7421
S	OPDEF	BSW	7002
C
C
C	[0] DISPATCH
S	DUMMY JX
S	DUMMY JY
S	DUMMY IOPR
S	ENTRY BFOLL
C
S	CPAGE 10
S JX,	BLOCK 2
S JY,	BLOCK 2
S IOPR,	BLOCK 2
C
S BFOLL,	BLOCK 2
C
C	GET THE ARGS
S	TAD I BFOLL
S	DCA JX
S	INC BFOLL#
S	TAD I BFOLL
S	DCA JX#
S	INC BFOLL#
C
S	TAD I JX
S	DCA \JX
C
S	TAD I BFOLL
S	DCA JY
S	INC BFOLL#
S	TAD I BFOLL
S	DCA JY#
S	INC BFOLL#
C
S	TAD I JY
S	DCA \JY
C
S	TAD I BFOLL
S	DCA IOPR
S	INC BFOLL#
S	TAD I BFOLL
S	DCA IOPR#
S	INC BFOLL#
C
S	TAD I IOPR
S	DCA \IOPR
C
C
	J=0
	K=0
C
C
C	DISPATCH
	GOTO (1,2,3,4), IOPR
C
C	[0.1] RETURN
2047	CONTINUE
S	RETRN BFOLL
C	[1] INIT THE (KMEM,KBYTE)
1	KMEM=JX
	KBYTE=JY
C
C	RESET THE PERIMETER COUNTERS
	IPERIMETER=0
	ISQPERIMETER=0
	GOTO 2047
C	[2] INIT THE FOLLOW SEGMENT COUNTER
2	CONTINUE
	NC=JY
C
	GOTO 2047
C	[3] INIT THE FIRST (X,Y)<==(JX,JY)
3	CONTINUE
C
C
	IXFIRST=JX
	IYFIRST=JY
	LSTX=JX
	LSTY=JY
	ITHETA=45
	GOTO 2047
C
C
C
C	[4] FOLLOW THE OUTSIDE BORDER 1 POINT.
4	CONTINUE
C
C
C	[4.1] GET NEIGHBORHOOD
	IX=LSTX
	IY=LSTY
C
C
C	GET NEIGHBORHOOD
	MEM=KMEM
	IBYTE=KBYTE
C
C	DO FRESH NEIGHBORHOOD FETCH
	CALL GETI1
C***********DEBUG*****
S	6344 /FBW4
S	AND (0100
S	SNA CLA
S	JMP \1997
	WRITE(3,1996)MEM,IBYTE,IX,IY
     1,I13,I12,I11,I14,I18,I10,I15,I16,I17
1996	FORMAT(' BFLW (BM,BY,X,Y)=',4I5,3(/,' ',3I4))
1997	CONTINUE
C******************************
C
C	[4.2] TEST IF ISOLATED PIXEL
C			THEN RETURN (-2,-2)==>(JXJY)
	IF(I10+I11+I12+I13+I14+I15+I16+I17)910,902,910
902	CONTINUE
C
	JX=-2
	JY=0
S	TAD \JX
S	DCA I JX
S	TAD \JY
S	DCA I \JY
	GOTO 2047
C
C
C	[4.3] FIND THE MINIMUM COMPUTING WINDOW
910	NUMBERTIMESAROUND=0
C
C
C	[4.4] DISPATCH ACCORDING TO ANGLE IN DEGREES
900	CONTINUE
S	TAD \ITHETA
S	MQL
S	CPAGE 2
S	DVI
S	55 /45 DECIMAL
S	CLA
C
C	0:315==>1:9
S	MQA
S	IAC /+1
S	DCA \IVAL
C
C
	GOTO(1000,1045,1090,1135,1180,1225,1270,1315),IVAL
C
C
C
C
C	[4.5.1.45]
1045	IF(I11-1)1000,645,745
745	IF(I11-NC)1000,845,1000
C	BEGIN "45 DEGREES"
645	ISQPERIMETER=ISQPERIMETER+1
845	IY=IY-1
	IX=IX+1
	JTHETA=1
	ITHETA=180
	GOTO 207
C	END "45"
C
C
C	[4.5.1.0]
1000	IF(I10-1)1315,600,700
700	IF(I10-NC)1315,800,1315
C	BEGIN "00 DEGREES"
600	IPERIMETER=IPERIMETER+1
800	IX=IX+1
	JTHETA=0
	ITHETA=90
	GOTO 207
C	END "00"
C
C
C	[4.5.1.315]
1315	IF(I17-1)1270,631,731
731	IF(I17-NC)1270,831,1270
C	BEGIN "315 DEGREES"
631	ISQPERIMETER=ISQPERIMETER+1
831	IY=IY+1
	IX=IX+1
	JTHETA=7
	ITHETA=90
	GOTO 207
C	END "315"
C
C
C	[4.5.1.270]
1270	IF(I16-1)1225,627,727
727	IF(I16-NC)1225,827,1225
C	BEGIN "270 DEGREES"
627	IPERIMETER=IPERIMETER+1
827	IY=IY+1
	JTHETA=6
	ITHETA=0
	GOTO 207
C	END "270"
C
C
C	[4.5.1.225]
1225	IF(I15-1)1180,622,722
722	IF(I15-NC)1180,822,1180
C	BEGIN "225 DEGREES"
622	ISQPERIMETER=ISQPERIMETER+1
822	IY=IY+1
	IX=IX-1
	JTHETA=5
	ITHETA=0
	GOTO 207
C	END "225"
C
C
C	[4.5.1.180]
1180	IF(I14-1)1135,618,718
718	IF(I14-NC)1135,818,1135
C	BEGIN "180 DEGREES"
618	IPERIMETER=IPERIMETER+1
818	IX=IX-1
	JTHETA=4
	ITHETA=270
	GOTO 207
C	END "180"
C
C
C
C	[4.5.1.135]
1135	IF(I13-1)1090,613,713
713	IF(I13-NC)1090,813,1090
C	BEGIN "135 DEGREES"
613	ISQPERIMETER=ISQPERIMETER+1
813	IY=IY-1
	IX=IX-1
	JTHETA=3
	ITHETA=270
	GOTO 207
C	END "135"
C
C
C
C	[4.5.1.90]
1090	IF(I12-1)209,690,790
790	IF(I12-NC)209,890,209
C	BEGIN "90 DEGREES"
690	IPERIMETER=IPERIMETER+1
890	IY=IY-1
	JTHETA=2
	ITHETA=180
	GOTO 207
C	END "90"
C
C
C
C
C
C
C	[4.6] TEST IF WENT AROUND TWICE
C		THEN FAIL
C		ELSE GOTO [4.5.45]
209	NUMBEROFTIMESAROUND=NUMBEROFTIMESAROUND+1
S	TAD (-2
S	TAD \NUMBERTIMESAROUND
S	SPA CLA
S	JMP \1045 /NOT YET
C
C
C	[4.6.1] GOT LOST CONTINUE ANYWAYS
	JX=-3
	JY=0
S	TAD \JX
S	DCA I JX
S	TAD \JY
S	DCA I JY
	GOTO 2047
C
C
C	[4.6.2] FOUND (IX,IY) TEST IF DONE.
207	CONTINUE
C	RETURN JTHETA IN THE MQ
S	TAD \JTHETA
S	MQL
C@C***********DEBUG*****
C@S	6344 /FBW4
C@S	AND (0040 /BIT 6
C@S	SNA CLA
C@S	JMP \1999
C@	JTHETA=JTHETA*45
C@	WRITE(3,1998)JTHETA,IX,IY,ITHETA
C@1998	FORMAT(' BFOLLOW[4.6.2] MOVED THETA=',I4,',[IX:IY]=[',I3,':',
C@     1I3,'], NEW THETA=',I4)
C@1999	CONTINUE
C@C*************************
C
C	SAVE LAST XY
	LSTX=IX
	LSTY=IY
C
C	PASS BACK (X,Y) AND TEST IF DONE
	JX=IX
	JY=IY
S	TAD \JX
S	DCA I JX
S	TAD \JY
S	DCA I JY
C
S	TAD \IX
S	CIA
S	TAD \IXFIRST
S	SZA CLA
S	JMP \2047 /NO
C
S	TAD \IY
S	CIA
S	TAD \IYFIRST
S	SZA CLA
S	JMP \2047 /NO
C
C
C	[4.7] YES,  DONE WITH FSM CLOSE OUT THE SEGMENT
	JX=-1
	JY=IPERIMETER+IFIX(1.41412*FLOAT(ISQPERIMETER))
S	TAD \JX
S	DCA I JX
S	TAD \JY
S	DCA I JY
	GOTO 2047
C	POINTERS
C	--------
C
C
C
C
	END
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