Physical Screen Size

[Luis]

Ok, what about attaching a scanner that you have already calibrated?
Should be easy to up the contrast and then scan for edges.

Another option would be to grab a pair of cheap electronic calipers and
hacking them onto a USB device to read the output values.

Alternatively: Hack a USB mouse and rig the H and V rollers to a table.
Then attach a 'pointer' to these rollers and read the H and V values as
the item is 'drawn' and translate them into the appropriate size  
(knowing
the dimensions of the table and calibrating accordingly). Hmmm, maybe
a graphics tablet would do, but it'd get damaged easily.

It would avoid the monitor getting damaged...!

I reckon the scanner would be the more accurate option and you can then
store that for each client.

I wouldn't count on the pixels being square by the way.

Cheers,

Luis.


On 30 Jan 2007, at 18:52, Walton Sumner wrote:

> I have a survey instrument which can require interface elements to  
> have
> exact physical lengths, especially a "visual analog scale" that is
> traditionally 10 cm. Not knowing what the screen settings will be  
> on client
> machines, I have for the time being put a button on the first  
> screen of the
> survey instrument that allows a survey administrator to drag it's  
> right edge
> until it is 2 cm long. Then anything else in the stack that needs an
> absolute size can be rescaled accordingly. You can put some  
> constraints on
> the assertions, like expecting no more than 100 pixels/2cm and no  
> less than
> 50 (one real value is 83 on this iMac). So far I've assumed that  
> pixels are
> squares, hope that's safe.
>
> As long as the survey instrument resides on a given machine, this is a
> one-time, set-and-forget event. The rev program reads instructions
> (including VAS lengths) in text files to implement new surveys, so the
> client holding the pixels/cm data should not be replaced very often.
>
> It is not at all elegant, but I expect that the obvious variations  
> on this
> theme are pretty reliable (eg, "How long is this line?", "Click 3  
> cm from
> the end of this line"), and perhaps less trouble for the user than  
> asking
> for several unfamiliar measurements. Still, if there is a  
> transparent way,
> I'd like to use it!
>
> To use the info that Luis found, it seems like you would have to  
> assert a
> pagerect in a print command, then get the printscale used in  
> printing the
> page, then calculate the absolute size of the card on screen. Has  
> anyone
> tried that?
>
> Seems like the simplest thing to do should be to read the diagonal  
> of used
> screen space from the hardware, but I do not see a rev command to  
> do that.
> Maybe there is a shell command to read the diagonal on some  
> systems, but I
> have not found it.
>
> Walton Sumner
>
>> Found this under the 'print' entry in the Rev Dictionary:
>>
>> 'The pageRect is the rectangle into which the card is printed, and
>> consists of four integers separated by commas: the left, top,  
>> right, and
>> bottom edges of the printed card, in points. (There are 72 points  
>> to an
>> inch.) The card is scaled to fit the specified pageRect. If you don't
>> specify a pageRect, the card's size depends on the printScale  
>> property.'
>>
>> Might help in calibrating the size.
>>
>> Cheers,
>>
>> Luis.
>>
>>
>>
>> Luis wrote:
>>> Hmmm, ok. What you could then do is open a dialogue box asking for
>>> dimensions (17 inch, 19 inch, etc), resolution, type (CRT, LCD or
>>> Plasma) and dpi. If the dpi is unknown by the user you could try to
>>> default to the most common dpi for that 'type' of monitor.
>>>
>>> Cheers,
>>>
>>> Luis.
>>>
>>>
>>> Mark Schonewille wrote:
>>>> Hi Luis,
>>>>
>>>> Yup, my main monitor is of the brand "unknown".
>>>>
>>>> Mark
>>>>
>>>> -- 
>>>>
>>>> Economy-x-Talk
>>>> Consultancy and Software Engineering
>>>> http://economy-x-talk.com
>>>> http://www.salery.biz
>>>>
>>>> Get your store on-line within minutes with Salery Web Store  
>>>> software.
>>>> Download at http://www.salery.biz
>>>>
>>>> Op 19-jan-2007, om 17:00 heeft Luis het volgende geschreven:
>>>>
>>>>> Hiya,
>>>>>
>>>>> If you can determine the monitor type you could probe a  
>>>>> database of
>>>>> configurations/resolution/dpi settings etc and then calculate the
>>>>> image size (using its coordinates) based on this information.
>>>>> I haven't looked into this but I reckon OSX and WXP have these  
>>>>> in the
>>>>> system somewhere (so they can 'plug and play').
>>>>>
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Luis.
>
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