option nolet
ask pixels z1,z2
print "----------------------------------------------------------"
print " graph pixel   : part 2c , sub,draw circle    version 1.0 "
print " peter.vlasschaert@gmail.com,18/02/2019                   "
print "----------------------------------------------------------"
print
!*******************************************
! filename : graphpixelpart2cfinalsub.tru 
!*******************************************
! online : help
! info : https://www.truebasic.com/node/1025
!*******************************************
xmin = -5
xmax = 5
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  => funcpict2c.bmp "
print "--------------------------------------------"
print
asp = x_pix/y_pix   ! aspect ratio
set window 0,(x_pix-1),(y_pix-1),0
set color "blue"
! draw axis
call draw_xas_usertopix(x_pix,y_pix,ymin,ymax)
call draw_yas_usertopix(x_pix,y_pix,xmin,xmax)
! draw F(x) => circle (parametric plot)
print " x = rr*cos(theta);y = rr*sin(theta), 'red '| cos(x) 'green' "
set color "red"
rr  = 70          ! radius circle
val = 0.01        ! step value
for theta = 0 to 6.28 step val
!*******************************
! parametric equation of circle
!*******************************
     x = rr*cos(theta)
     y = rr*sin(theta)
!call convers_usertopix(x_pix,y_pix,xmin,xmax,ymin,ymax,x,y,px,py)
     plot x_pix/2+x,y_pix/2+y
next theta
set color "green"
for  x = xmin to xmax step val
     y = cos(x) 
call convers_usertopix(x_pix,y_pix,xmin,xmax,ymin,ymax,x,y,px,py)
     plot px,py
next x
!***********************************
! box :  xl < x < xr , yt < y < yb *
!***********************************
box keep x_pix/2-rr,x_pix/2+rr,y_pix/2-rr,y_pix/2+rr in kep1$
!***********************************************
! draw box " circle + some parts of the circle "
!***********************************************
! syntax : PLOT TEXT, at -1, 5 : "Test Results"
!***********************
! fourth : quadrant  =>*
!***********************
cor = 10   ! correct display text
BOX SHOW kep1$ at x_pix/2+3*rr,y_pix/2+3*rr ! Draw at new position (+,+)
set color "red"
PLOT TEXT, at x_pix/2+3*rr, y_pix/2+3*rr+cor  : "fourth qudrant  :pos circle (+,+)"
!***********************
! second : quadrant  =>*
!***********************
BOX SHOW kep1$ at x_pix/2-3*rr,y_pix/2-3*rr ! Draw at new position (-,-)
set color "blue"
PLOT TEXT, at x_pix/2-3*rr, y_pix/2-3*rr+cor  : "second quadrant :pos circle (-,-)"
!***********************
! first : quadrant   =>*
!***********************
BOX SHOW kep1$ at x_pix/2+3*rr,y_pix/2-3*rr ! Draw at new position (+,-)
set color "green"
PLOT TEXT, at x_pix/2+3*rr, y_pix/2-3*rr+cor : "first quadrant   :pos circle (+,-)"
!***********************
! thrid : quadrant   =>*
!***********************
BOX SHOW kep1$ at x_pix/2-3*rr,y_pix/2+3*rr ! Draw at new position (-,+)
set color "black"
PLOT TEXT, at x_pix/2-3*rr, y_pix/2+3*rr+cor : "third quadrant   :pos circle (-,+)"

!************************************************
! How to save canvas as a picture. (funcpict.bmp)
!************************************************
call save_pixfullwin(z1,z2,keep$)
!------------------------------------------------------------------------,
!  Create a filename. Don't need an extention; the SUB will put ".bmp"
!------------------------------------------------------------------------,
ff$="C:\download\funcpict2c.bmp" ! make sure this is a valid path...
CALL Write_Image("MS BMP", keep$, ff$) ! or you can use this 

print
end

sub save_pixfullwin(z11,z22,kep$)
! <help> 
! z11 : number of pixels x-direction , start :0 to z11-1,integer >0
! z22 : number of pixels y-direction , start :0 to z22-1,integer >0
! picture hold string : kep$
!************************************************
box keep 0, z11-1, z22-1, 0 in kep$ ! kep$ memory
end sub

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 convers_usertopix(z11,z22,x_min,x_max,y_min,y_max,xx,yy,pxx,pyy)
! < help >
! z11 : number of pixels x-direction , start :0 to z11-1,integer >0
! z22 : number of pixels y-direction , start :0 to z22-1,integer >0
! x-direction : x_min < =  x < = x_max , float
! y-direction : y_min < =  y < = y_max , float
! pxx,pyy : integer > 0
!********************************************************************
dx = (x_min-x_max)
dy = (y_min-y_max)
pxx=(z11*x_min)/dx-(xx*z11)/dx
pyy=(yy*z22)/dy-(z22*y_max)/dy
end sub

sub draw_xas_usertopix(z11,z22,y_min,y_max)
! < help >
! z11 : number of pixels x-direction , start :0 to z11-1,integer >0
! z22 : number of pixels y-direction , start :0 to z22-1,integer >0
! y-direction : y_min < =  y < = y_max , float
!*******************************************************************
dy = (y_min-y_max)
pxa=0
pxb=z11
pxc=-(z22*y_max)/dy
plot lines : pxa,pxc ;pxb,pxc
end sub

sub draw_yas_usertopix(z11,z22,x_min,x_max)
! < help >
! z11 : number of pixels y-direction , start :0 to z11-1,integer >0
! z22 : number of pixels y-direction , start :0 to z22-1,integer >0
! x-direction : xmin < =  x < = x_max , float
!*******************************************************************
dx = (x_min-x_max)
pxaa=z22
pxbb=0
pxcc=(z11*x_min)/dx
plot lines : pxcc,pxaa ;pxcc,pxbb
end sub