|Syntax||DRAW x1,y1 TO x2,y2 ,colour|
|Location||Fast PLOT/DRAW Toolkit|
This command draws a line in absolute co-ordinates on the screen. Any windows and window attributes are ignored. x1 and x2 range from 0 to 511, y1 and y2 from 0 to 255. DRAW uses the screen base address defined with SCRBASE (which enables it to draw on a screen stored in memory as well as the currently visible screen. It is therefore compatible with QL emulators and Minerva’s dual screen mode, although it cannot support higher resolutions). The range for the colour parameter is 0..7, other values give odd results without being dangerous.
Here is a procedure which draws a line given in polar co-ordinates. A point in a polar system is specified by a radius and angle.
170 DEFine PROCedure POLAR_DRAW (r1,phi1,r2,phi2,col) 180 REMark less precise but fast version 190 LOCal r,phi,r_old,phi_old,dr,dphi 200 LOCal x1,x2,y1,y2,dist 210 r_old=r1: phi_old=phi1 220 r=r1: phi=phi1 230 x1=1.35*r_old*SIN(phi_old+PI/2)+255 240 y1=r_old*COS(phi_old+PI/2)+127 250 dist=(r1+r2)/2 * (phi1+phi2)/PI 260 IF dist==0 THEN RETurn 270 dr=(r2-r1)/dist: dphi=(phi2-phi1)/dist 280 REPeat Drawing 290 IF r>=r2 AND phi>=phi2 THEN EXIT Drawing 300 r=r_old+dr: phi=phi_old+dphi 310 x2=1.35*r*SIN(phi+PI/2)+255 320 y2=r*COS(phi+PI/2)+127 330 DRAW x1,y1 TO x2,y2 ,col 340 r_old=r: phi_old=phi 350 x1=x2: y1=y2 360 END REPeat Drawing 370 END DEFine POLAR_DRAW
POLAR_DRAW 0,0 TO 100,8*PI ,7
draws an archimedic spiral and these few lines create a polar pattern:
10 SCLR 0 20 FOR a=0 TO 50 STEP 10 30 POLAR_DRAW a,0 TO a,2*PI ,7 40 POLAR_DRAW 0,PI*a/25 TO 50,PI*a/25, 7 50 END FOR a 60 REFRESH
DRAW is specific to the resolution of 512x256 pixels. It can however be used to draw on Minerva’s second screen by using the command SCRBASE SCREEN(#3) (assuming that #3 is open on the second screen).
|Syntax||DRAW [#ch,] x2,y2|
|Location||DRAW (DIY Toolkit - Vol G)|
This command draws a line in absolute co-ordinates on the screen with reference to the specified window channel (if any - default #1). The line is drawn from the last point plotted with the PLOT command from the same toolkit, to the point specified by x2,y2. This is quicker than using the SuperBASIC LINE command and unlike other similar commands, it will support the current INK colour and OVER mode.
<CTRL><F5> will pause the line drawing and it will even work in MODE 4, 8 and 12 (on the THOR XVI, provided that you have v1.6+). The main limitation on this command is that the line must appear fully within the specified window, so x2 and y2 cannot exceed the width or height of the specified window (in pixels) nor be less than zero.
Although DRAW will work wherever the screen base is located, it assumes that a line of pixels takes 128 bytes - it will not therefore currently work on higher resolutions.