option nolet
ask pixels z1,z2
print "----------------------------------------------------------"
print " graph pixel   : part 2a ,                    version 1.0 "
print " peter.vlasschaert@gmail.com,10/02/2019                   "
print "----------------------------------------------------------"
! filename : graphpixelpart2afinal.tru    
xmin = -5
xmax = 5
ymin = -7
ymax = 7
x_pix = z1
y_pix = z2
print
print "--------------------------"
print " draw a function y = F(x) "
print "--------------------------"
print
print "-------------------------------------------"
print " How to save pixel window  => funcpict.bmp "
print "-------------------------------------------"
print
set window 0,z1-1,z2-1,0
set color "blue"
! draw axis
pxa=0
pxb=x_pix
pxc=-(y_pix*ymax)/(ymin-ymax)
plot lines : pxa,pxc ;pxb,pxc
pxaa=y_pix
pxbb=0
pxcc=(x_pix*xmin)/(xmin-xmax)
plot lines : pxcc,pxaa ;pxcc,pxbb
! draw F(x) =>
print " x: ->  y = sin(x) 'red ',cos(x) 'green' "
set color "red"
val = 0.01
for  x = xmin to xmax step val
     y = sin(x) 
     px=(x_pix*xmin)/(xmin-xmax)-(x*x_pix)/(xmin-xmax)
     py=(y*y_pix)/(ymin-ymax)-(y_pix*ymax)/(ymin-ymax)
     plot px,py
next x
set color "green"
for  x = xmin to xmax step val
     y = cos(x) 
     px=(x_pix*xmin)/(xmin-xmax)-(x*x_pix)/(xmin-xmax)
     py=(y*y_pix)/(ymin-ymax)-(y_pix*ymax)/(ymin-ymax)
     plot px,py
next x
!************************************************
! How to save canvas as a picture. (funcpict.bmp)
!************************************************
box keep 0, z1-1, z2-1, 0 in keep$ ! area for the picture (*.bmp)
!------------------------------------------------------------------------,
!  Create a filename. Don't need an extention; the SUB will put ".bmp"
!------------------------------------------------------------------------,
ff$="C:\download\funcpict.bmp" ! make sure this is a valid path...
CALL Write_Image("MS BMP", keep$, ff$) ! or you can use this 
print
end