Re: Subject: WYSIWIG drawing vs printing (was drawing scaled lines)
Re: Subject: WYSIWIG drawing vs printing (was drawing scaled lines)
- Subject: Re: Subject: WYSIWIG drawing vs printing (was drawing scaled lines)
- From: John Stiles <email@hidden>
- Date: Fri, 7 Jan 2005 15:39:21 -0800
That's nice from a computer-science perspective, but if you want to draw something on-screen that's an
actual inch, it's not helpful information. You need to scale things to match the monitor DPI. This should be as simple as a transformation matrix with a scale factor in it—which, of course, you wouldn't apply when printing.
On Jan 7, 2005, at 3:31 PM, Erik M. Buck wrote:
I am shocked that it has not been stated already or I missed it.
Quartz 2D is DEVICE INDEPENDENT!
Pixels are irrelevant.
DPI of the output device is irrelevant.
Only "real world" distance units like inches, centimeters, miles, yards,
light-years, and Postscript Points are relevant.
In an unscaled Quartz 2D coordinate system a distance of 1.0 is one
Postscript Point which is defined a 1/72 Inch.
To draw a one inch long line on any output device including a 300 DPI
printer or a 2000 DPI printer or a 100 DPI screen, draw a line that is 72
units long in an unscaled Quartz 2D coordinate system.
Because printers are calibrated, the printed line will be one inch long as
measured with a standard ruler.
Because computer displays are NOT calibrated and in fact CRTs can vary with
temperature and time, the 1 inch line drawn will not be one inch long as
measured with a standard ruler, but it will be one inch long as measured by
a ruler that is also drawn by Quartz in an unscaled coordinate system.
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