Bitmap/Midpoint circle algorithm: Difference between revisions

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<br>a good aspect ratio.

The program automatically shows all of the plot's points by finding the minimum and maximum X,Y coördinates.

The program automatically shows all of the plot's points by finding the minimum and maximum   '''X''','''Y'''   coördinates.

<lang rexx>/*REXX program plots three circles using midpoint/Bresenham's circle algorithm. */

@.= '·' /*fill the array with middle─dots char.*/

minX=0; maxX=0; minY=0; maxY=0 /*initialize the minimums and maximums.*/

minX= 0; maxX= 0; minY= 0; maxY= 0 /*initialize the minimums and maximums.*/

call drawCircle 0, 0, 8, '#' /*plot 1st circle with pound character.*/

call drawCircle 0, 0, 11, '$' /* " 2nd " " dollar " */

call drawCircle 0, 0, 19, '@' /* " 3rd " " commercial at. */

border=2 /*BORDER: shows N extra grid points.*/

border= 2 /*BORDER: shows N extra grid points.*/

minX=minX-border*2; maxX=maxX+border*2 /*adjust min and max X to show border*/

minX= minX - border*2; maxX= maxX + border*2 /*adjust min and max X to show border*/

minY=minY-border ; maxY=maxY+~~border~~ /* " " " " Y " " " */

minY= minY - border ; maxY= maxY + border /* " " " " Y " " " */

if @.0.0==@. then @.0.0='┼' /*maybe define the plot's axis origin. */

if @.0.0==@. then @.0.0= '┼' /*maybe define the plot's axis origin. */

/*define the plot's horizontal grid──┐ */

do h=minX to maxX; if @.h.0==@. then @.h.0='─'; end /* ◄───────────┘ */

do h=minX to maxX; if @.h.0==@. then @.h.0= '─'; end /* ◄───────────┘ */

do v=minY to maxY; if @.0.v==@. then @.0.v='│'; end /* ◄──────────┐ */

do v=minY to maxY; if @.0.v==@. then @.0.v= '│'; end /* ◄──────────┐ */

/*define the plot's vertical grid───┘ */

do y=maxY by -1 to minY; _= /* [↓] draw grid from top ──► bottom.*/

do x=minX to maxX; _=_ || @.x.y /* ◄─── " " " left ──► right. */

do x=minX to maxX; _= _ || @.x.y /* ◄─── " " " left ──► right. */

end /*x*/ /* [↑] a grid row should be finished. */

say _ /*display a single row of the grid. */

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/*──────────────────────────────────────────────────────────────────────────────────────*/

drawCircle: procedure expose @. minX maxX minY maxY

parse arg xx,yy,r 1 y,plotChar; fx=1; fy=-2*r /*get X,Y coördinates*/

parse arg xx,yy,r 1 y,plotChar; fx= 1; fy= -2*r /*get X,Y coördinates*/

f=1-r

f= 1 - r

do x=0 while x<y /*~~▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒~~*/

do x=0 while x<y /*▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒*/

if f>=0 then do; y=y-1; fy=fy+2; f=f+fy; ~~end~~ /*▒*/

if f>=0 then do; y= y - 1; fy= fy + 2; f= f + fy; end /*▒*/

~~fx=fx+2;~~ ~~f=f+fx~~ /*▒*/

fx= fx + 2; f= f + fx /*▒*/

call plotPoint xx+x, yy+y /*▒*/

call plotPoint xx+y, yy+x /*▒*/

call plotPoint xx+y, yy-x /*▒*/

call plotPoint xx+x, yy-y /*▒*/

call plotPoint xx-y, yy+x /*▒*/

call plotPoint xx-x, yy+y /*▒*/

call plotPoint xx-x, yy-y /*▒*/

call plotPoint xx-y, yy-x /*▒*/

end /*x*/ /* [↑] place plot points ══► plot.~~▒▒▒▒▒▒▒▒▒▒▒▒▒~~*/

end /*x*/ /* [↑] place plot points ══► plot.▒▒▒▒▒▒▒▒▒▒▒▒*/

return

/*──────────────────────────────────────────────────────────────────────────────────────*/

plotPoint: parse arg c,r; @.c.r=~~plotChar~~ /*assign a character to be plotted. */

plotPoint: parse arg c,r; @.c.r= plotChar /*assign a character to be plotted. */

minX=min(minX,c); maxX=max(maxX,c) /*determine the minimum and maximum X.*/

minX= min(minX,c); maxX= max(maxX,c) /*determine the minimum and maximum X.*/

minY=min(minY,r); maxY=max(maxY,r) /* " " " " " Y.*/

minY= min(minY,r); maxY= max(maxY,r) /* " " " " " Y.*/

return</lang>

'''output'''

<pre>

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