[mapserver-users] layer mask without clipping

[Lars Lingner]

Hi Thomas,

On 25.02.2014 11:11, thomas bonfort wrote:
> Lars,
> I don't understand what you're trying to obtain. Can you clarify
> and/or post a couple screenshots?
> 

In the image [1]  you can see a district (10e Arrondissement) in Paris
and his surrounding. The area of interest is only the district, which I
marked with a dotted line in gimp. Everything outside is rendered
differently, here in gray scale. But also some kind of hatching or a
colored transparent overlay would be thinkable. But only for the
unmasked area (outside) - the masked area (inside) should use the
original style.

My current work flow is
a) render the whole area with the gray style
b) render the district (applied mask) with the colored style
c) put b) on top of a) with image processing software

I probably should mention that this isn't for a interactive map, just
for one time rendering.

My first try was slightly different, which raises a issue at the border:

a) render the masked area
b) render everything else (masked area is a whole)
c) put a) and b) together

When you look at the result [1] you see
- doubled labels (blue A)
here was the feature labeled in the both (masked and inverted mask) and
they are overlapping

- cut labels (blue B)
The rendered label of the inverted mask is actually placed partially in
the masked area

I acknowledge these aren't issues at all when you stick to clipping the
mask. Don't know why I'm attracting lots of special use cases, but
then... this is what keeps my work with MapServer interesting. :)


Thanks for listening,

Lars


[1] http://s1.directupload.net/images/140226/w2kjgxbm.png