I used this method to the offset value on my laptop which has a screen
resolution of 1280x800 running QPC2
WINDOW SCR_XLIM,SCR_YLIM,0,0
SCALE 800,0,0
offset = ((SCR_XLIM-SCR_YLIM)*2)/SCR_XLIM
this gives offset a value of .75 which when applied to
CIRCLE 100,100,50,offset,0 draws a good circle and square when x value is
also *offset, however I found by trial and error that taking off
0.01 from the 0.75 offset it was slightly more accurate at 0.74
and approximately 1/.74 = 1.35
on a 512x256 window SCALE of 256,0,0
the offset worked out to be = 1
Lee Privett
-------------------------------------------------------------
Sent from my Laptop running XP
but emulating the QL using QPC2
----- Original Message -----
From: "Rich Mellor" <[email protected]>
To: <[email protected]>
Sent: Sunday, January 16, 2011 3:58 PM
Subject: Re: [Ql-Users] scale and drawing on the QL
On 16/01/2011 15:39, gdgqler wrote:
On 16 Jan 2011, at 14:55, Lee Privett wrote:
Hey people, has anyone come across any articles or information that
allows the use of the line or circle command that draws to the screen
accurately accoding the known dot resolution?
Let me explain
Say you have a maximum screen of 1280w800h, and a window#1 of
1280x800x0x0
Using a SCALE command of 800,0,0 allows drawing a line from 0 to 768
that reaches from the bottom to the top accurately but the x value is
way off screen drawing to 1280
I have my own formulae for an x multiplication factor that seems to work
well making squares appear square on the screen and circles appear
circular on the screen as well, but not being a mathematics person my
formulae is not very scientific and I have yet to check it on larger
screens where any errors would be magnified.
It seems however to work on standard QL screen of 512x256 well. I was
just wondering before I explore any further if anyone else had writen
anything on it or if anyone had any comments?
As it happens I am just in the process of looking at this problem. The
problem is twofold. First the pixels may not be square. Indeed they
differ in shape between a Q40/60 and QPC2. Different sizes of Aurora
give different shapes too. The second problem is that the graphics
coordinates have a different effective size from pixels. I wanted to draw
lines using graphics between two points defined by pixel positions. This
is the reverse of trying to annotate diagrams drawn by the graphics
commands. SCALE x,y,a,b allows that. To draw lines between two pixel
positions is possible by setting SCALE h,0,0, where h is the height of
the window in pixels. The graphics coordinates of pixel position x, y
become x/1.35, h-y. This seems to work on Q60 and QPC2.
Circles and squares on a Q60 are ellipses and oblongs on QPC2 and
differing sizes of screen with Aurora. I found by trial and error values
that made circles circular and oblongs square. I don't know of any other
method. It depends on the shape of pixels and I don't know where that is
defined.
George
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From memory, my program should take account of the different shape of
pixels....
--
Rich Mellor
RWAP Services
http://www.rwapsoftware.co.uk
http://www.rwapservices.co.uk
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