Back|Forward

DCL:GRPH2:UEPACK: Tone Fill Routines: Explanation of Subroutines

9.2.3 UEGTLA

1.

Function

Sets the value of the tone level used by UETONE by the minimum & maximum values and step size, or by the number of levels.

2.

Call

CALL UEGTLA(XMIN,XMAX,DX)

3.

Explanation of Parameters

XMIN, XMAX	(R)	The minimum and maximum values of the tone levels. The levels do not necessarily need to have conveniently rounded numbers.
DX	(R)	When DX<0, uses DX as the step size.
		When DX=0, inquires 'NLEV' and generates approximately NLEV tone levels.
		When DX>0, generates approximately INT(ABS(DX)) tone levels.

4.

Notes

(a)

This routine uses the same algorithm as UDGCLA (see Section 8.2.3) to generate the level values. To unify the algorithm,  the same internal variables as 'NLEV' and 'ICYCLE' used in UDPACK are provided in UEPACK. When these variables are changed in the UDPACK, they must also be changed in the UEPACK.

(b)

Must be XMIN != XMAX.

(c)

The tone level is set as the step size specified by DX multiplied by an integer factor.

(d)

The difference in the values of color indices specified by the internal variables 'ICOLOR1' and 'ICOLOR2' (the initial values are 15 and 94, respectively) is divided by the number of tone levels to obtain the color index for each level. The pattern index  'ITPAT' (initial value is 999: solid fill) is added to the color index  to generate the tone pattern index. for the level.