option nolet
ask pixels z1,z2
print "---------------------------------------------------------------------"
print " user coord.   : part 3 ,sub,draw circle,aspect ratio    version 1.0 "
print " peter.vlasschaert@gmail.com,19/02/2019                              "
print "---------------------------------------------------------------------"
print
!*******************************************
! filename : graphuserpart3finalsub.tru 
!*******************************************
! online : help
! info : https://www.truebasic.com/node/1025
!*******************************************
xmin = -7
xmax = 7
ymin = -7
ymax = 7
dx = xmax-xmin
dy = ymax-ymin
x_pix = z1
y_pix = z2
print
print "--------------------------"
print " draw a function y = F(x) "
print "--------------------------"
print
print "--------------------------------------------"
print " How to save pixel window  => funcpict3.bmp "
print "--------------------------------------------"
print
! draw F(x) => circle (parametric plot)
print " x = rr*cos(theta);y = rr*sin(theta), 'red '| cos(x) 'green' "
asp = x_pix/y_pix   ! aspect ratio
set window xmin,xmax,ymin,ymax
!********************************
! parametric plot of circle "red"
!********************************
set color "red"
rr  = 1           ! radius circle
val = 0.01        ! step value
!*************************************
! need have same axis for both x and y
!*************************************
for theta = 0 to 6.28 step val
!*******************************
! parametric equation of circle
!*******************************
     x = rr*cos(theta)
     y = rr*sin(theta)
 plot points :x,y*asp
next theta
!******************************
! F(x) =>
!******************************
set color "green"
for  x = xmin to xmax step val
     y = cos(x) 
     plot x,y*asp
next x
!******************************
! draw x-axis and y-axis
!******************************
set color "blue"
call draw_xas_user(xmin,xmax)
call draw_yas_user(ymin,ymax)
!***********************************
! box :  xl < x < xr , yb < y < yt *
!***********************************
! corrected with asp 'see above
box keep 0-rr,0+rr,(0-rr)*asp,(0+rr)*asp in kep1$
!*************************************************
! draw box " circle + some parts of the function "
!*************************************************
cor = 0.5 ! corrected position txt
#!*************************************************
#! math : first quadrant (x>0,y>0), also here.
#!*************************************************
BOX SHOW kep1$ at 1,1 ! Draw at new position circle
set color "black"
PLOT TEXT, at 1+cor,1-cor : "new circle"

!************************************************
! How to save canvas as a picture. (funcpict.bmp)
!************************************************
call save_userfullwin(xmin,xmax,ymin,ymax,keep$)
!------------------------------------------------------------------------,
!  Create a filename. Don't need an extention; the SUB will put ".bmp"
!------------------------------------------------------------------------,
ff$="C:\download\funcpict3.bmp" ! make sure this is a valid path...
CALL Write_Image("MS BMP", keep$, ff$) ! or you can use this 
print
end

sub save_userfullwin(x_min,x_max,y_min,y_max,kep$)
! <help>
! x-direction : x_min < =  x < = x_max , float
! y-direction : y_min < =  x < = x_max , float
! picture hold string : kep$
!***************************************************
box keep x_min, x_max, y_min, y_max in kep$ ! kep$ memory
end sub


sub draw_xas_user(x_min,x_max)
! <help>
! x-direction : x_min < =  x < = x_max , float
! picture hold string : kep$
!***************************************************
pxa = 0
pxb = x_min
pxc = 0
pxd = x_max
plot lines : pxa,pxb ;pxc,pxd
end sub

sub draw_yas_user(y_min,y_max)
! <help>
! y-direction : y_min < =  x < = x_max , float
! picture hold string : kep$
!***************************************************
pxaa = y_min
pxbb = 0
pxcc = y_max
pxdd = 0
plot lines : pxaa,pxbb ;pxcc,pxdd
end sub