[Mapserver-dev] Label rotation...

[Stephen Woodbridge]

We could add an addition option to CW, CCW, COMPASS where COMPASS would 
be zero north and CW.

Sorry, I meant CW not CC in my earlier post, but I guess you figured 
that out ;)

-Steve

Paul Ramsey wrote:

> Yes, I always considered the label behavior correct, because here in BC 
> our toponymy comes with CCW label angles, so applying them directly gave 
> me the "correct" looking results. If you invert the behavior then I have 
> to negate all my input values before drawing :)
> 
> Unfortunately there is no standard here, people will definately have 
> angles of both sorts. (And different start points for measurement too... 
> start at north, or start at the positive X axis?)
> 
> P.
> 
> Stephen Woodbridge wrote:
> 
>> Steve Lime wrote:
>>
>>> Just ran into an issue with GD. I probably knew about it but never
>>> really considered it a problem until working on a specific issue
>>> recently. Anyway, GD interprets angles in a counter-clockwise fashion.
>>> So, if you take the letter 'A' and rotate it 90 degrees it points west
>>> instead of east. That's counter intuitive if you're used to compass
>>
>>
>>
>> But exactly what is expected if you are used to vector algebra.
>>
>>> bearings or if you're using labels for "pointing". The fix, for labels
>>> at least, is to simply negate the angle before passing to GD. What do
>>> folks think?
>>
>>
>>
>> What angles are we talking about? Would this change mean that it would 
>> change the sense of angle for all existing mapfiles? What happens to 
>> people that have angles in their attribute fields?
>>
>>> Note the docs are do not specify a rotation direction...
>>
>>
>>
>> What about adding an optional CC and CCW argument to angles in the 
>> mapfile with the default being the CCW like it is today. For example:
>>
>> ANGLE 90
>> ANGLE 90 CC
>> ANGLE 90 CCW
>>
>> or better because it would work with LABELANGLEITEM
>>
>> ANGLE 90
>> ANGLE CC 90
>> ANGLE CCW 90
>> ANGLE CC
>> ANGLE CCW
>>
>> Where the last two would be used anywhere a _____ANGLEITEM field is 
>> specific.
>>
>> or also add CC and CCW as trailing optional fields to _____ANGLEITEM 
>> like:
>>
>> LABELANGLEITEM "myangles" [CC|CCW]
>>
>> -Steve W.
>>
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> 
> 
>