Re: Again: canvas size

[Harald H. <h.h...@tu...>]

On Wed, 12 Oct 2005, Ethan Merritt wrote:

> On Wednesday 12 October 2005 06:34 am, Harald Harders wrote:
> > set xscreenrange [0:1]
> > set yscreenrange [0:2]
> >
> > Have a look at http://www.harald-harders.de/gnuplot/canvas/
>
> I remain unconvinced.
>
> The only reason that your plots need to have these odd screen
> ranges is that they specify per-plot arrows in terms of
> screen coordinates rather than graph coordinates.
>
> If you don't want the arrow to scale with the screen size,
> then why are you specifying them in screen coordinates?

Because I also do not want them to scale with the graph size. I do want to
have arrows that have the same length in absolute coordinates, say mm or
inches. I use larger canvas sizes mainly for multiplots where two plots
are above each other, often with different heights. And all these plots,
single plots and multiplots have the same arrow lengths. Of course I could
use 'character' as absolute measure which does not scale with the canvas
size, but there is no fixed relation between x and y length.

Until now, the screen coordinates are the only measure (except character,
see above) that can remain constant independent on the graph, canvas or
whatever size. If the screen coordinate system is changed to be hardcoded
to range 0:1 the only absolute coordinate system gets lost.

And I also do not see why there shall not be a coordinate system that
allows two plots to have identical sizes independently on the canvas size.

Where is the advantage of generating two plots with the same size by
giving different measures:

set terminal png size 640,480
set multiplot
set size 1,1
...

and

set terminal png size 640,600
set multiplot
set size 1,480./600

I do not understand this.

I do not understand your reluctance against a coordinate system with an
absolute manner. In particular because I also agree that the default
should be that the screen coordinate system scale with the canvas.
Maybe, we have a different view of the canvas size. For you it appears to
be a scaling factor for the plots (but for that, I really can rescale my
output in standard size). For me, the canvas size is the size of an area
where I can put everything. If you use A3 paper instead of A4 paper, you
still have the possibility of plotting a square of 10 x 10 mm. You do not
have to say: "I plot a square of 10/sqrt(2) * 10/sqrt(2) A3-mm".

I of course would also agree with a new coordinate system that may really
use absolute coordinates as millimeters. But this seems not to be possible
because many terminals do not have this measure.

So, why not a coordinate system that's unit is constant, x mm for
Postscript, y Pixel for screen or pixel terminals independent on canvas
size?  And because pixel are not defined in postscript and inches,
millimeter, and pt are not defined for screen terminals (while they were
defined for pixel-based terminals if the resolution could be given), a
pragmatic default scaling has to be defined. And why not using range 0 to
1 for the default canvas size?

Maybe, a measure millimeter should be introduced that used a resolution
for pixel-based terminals and either the resolution of the window manager
or a fall-back of 75 or 72 dpi for screen terminals.

I am strict against to dispose a coordinate system that stays constant
when resizing the canvas.

I assume that you still are not convinced but I nevertheless hope so.

Best regards
Harald

-- 
Harald Harders
h.h...@tu...
http://www.harald-harders.de