C****************************************************************
C* 								*
C*								*
C*	DIGITAL EQUIPMENT CORPORATION ASSUMES NO RESPONSIBILITY *
C*	EITHER FOR THE CREATION OR FOR THE CLINICAL EFFICACY	*
C*	OF THIS PROGRAM. USERS MUST ASSUME FULL RESPONSIBILITY	*
C*	FOR ANY RESULTS OR DIAGNOSES OBTAINED FROM THE USE	*
C*	OF THIS PROGRAM. QUESTIONS ON THE EXECUTION OF THIS	*
C*	PROGRAM MUST BE REFERRED BACK TO THE ORIGINAL AUTHOR.	*
C*								*
C* AUTHOR:	SALLY FORSTER					*
C*		C/O DEPARTMENT OF NUCLEAR MEDICINE		*
C*		GUY'S HOSPITAL				*
C*		LONDON, ENGLAND					*
C*								*
C*		TEL: 01-407-7600 EXT 2583/4			*
C*								*
C****************************************************************
	SUBROUTINE INTERP(AINTER,AX0,AX1,AY0,AY1,ICOLC,ICOLT)
C*****DRAW A STRAIGHT LINE FROM AX0,AY0 TO AX1,AY1 IN COLOUR ICOLT
	IMPLICIT LOGICAL*1 (A)
	IMPLICIT INTEGER*2 (D-Z)
	Y2=AY1.AND."000377
	Y1=AY0.AND."000377
	X2=AX1.AND."000377
	X1=AX0.AND."000377
	IF(.NOT.AINTER)GOTO50
	IF(X1.EQ.X2)GOTO20
C*****CM IS GRADIENT
	CM=FLOAT(Y2-Y1)/FLOAT(X2-X1)
C*****CB IS INTERCEPT
	CB=FLOAT(Y2)-CM*FLOAT(X2)
C*****PLOTS ALL POINTS FROM X1 TO X2
	OJ=INT(CM*FLOAT(X1)+CB)
	DO 10 I=X1,X2
	II=I
	J=INT(CM*FLOAT(I)+CB)
	IF(OJ-J)3,10,5
3	N=1
	GOTO 7
5	N=-1
C*****FILL IN ANY SPARE Y COORDS
7	OJ=OJ+N
	IF(OJ.EQ.J)GOTO 10
	CALL PLOTB(II,OJ,1,ICOLC,ICOLT)
	GOTO 7
10	CALL PLOTB(II,J,1,ICOLC,ICOLT)
	RETURN
C*****VERTICAL LINE
20	IF(Y2-Y1)30,50,40
30	N=-1
	GOTO 45
40	N=1
45	J=Y1-N
47	J=J+N
	CALL PLOTB(X1,J,1,ICOLC,ICOLT)
	IF(J.EQ.Y2)RETURN
	GOTO47
C*****SINGLE POINT
50	CALL PLOTB(X1,Y1,1,ICOLC,ICOLT)
	RETURN
	END