Right, you can not rely on the tileindex from doing anything more than
say these are the objects that intersect with your bbox.
There are no specific controls over how the objects interact other than
items are draw in the order they are found in the data sources. This is
why sorting efected your example.
Explicitly burning NODATA or mask bands is the right way to control the
images if your need that.
-Steve W
On 1/19/2017 1:08 PM, Peter Schmitt wrote:
Thanks for the sortshp tip! You are correct -- sorting the tileindex
yields the result I expected.
If the black pixels cover the full extents of black.tif (ie. with zero
NODATA values), then Mapserver will render either an all black or an all
gray image, regardless of the sorting order in the non-overlapping
geometries in the tileindex. When I internally tile the source images
and zoom in, Mapserver does something curious: If the intersection
between the tileindex and the requested bbox contain a single record,
Mapserver will render the correct image. When I zoom in, Mapserver
renders an aliased image on the 256x256 WMS requests sent by the
client. I would guess the requested BBOX is intersected with the
tileindex. When the intersection yields a single item in tileindex, it
renders the correct image. When there are two items in the intersection
of the requested BBOX and tileindex, the images are painted over the
full requested BBOX in the order provided by the tileindex.
I also could not find any docs/requirements on a tileindex guaranteeing
ordering of the stacking images returned by the tileindex... so I guess
it's best to not rely on this and just burn in NODATA/an external mask
to my source images if I need such behavior.
Thanks again,
Pete
On Thu, Jan 19, 2017 at 4:31 AM, thomas bonfort
<thomas.bonf...@gmail.com <mailto:thomas.bonf...@gmail.com>> wrote:
Peter, if I understand correctly....
I'm not aware that there is any documentation or requirement that
using a tileindex with mapserver garantees any ordering in the
stacking of the images returned by the tileindex. Namely, if your
tileindex returns your gray (opaque) image after (i.e. on top of)
your black/white image, then your black/white image will be
completely obscured by your gray image.
This is what I'd try:
- try using the sortshp utility on your tileindex (once in ascending
order, once in descending) and see if the resulting image is affected
- use a postgis based tileindex layer with explicit ORDER BY clauses
to enforce that transparent images get rendered after opaque ones
--
thomas
On Thu, Jan 19, 2017 at 12:31 AM Peter Schmitt <pschm...@gmail.com
<mailto:pschm...@gmail.com>> wrote:
Hi,
I have a tile index to render a layer from two images. The
images are black.png
https://github.com/pedros007/mapserver-tindex-problem/blob/master/black.png?raw=true
<https://github.com/pedros007/mapserver-tindex-problem/blob/master/black.png?raw=true>
which has NODATA values over the white areas and grayscale
pixels with intensity 1 and gray.png with intensity 128 and zero
NODATA values in the image
https://github.com/pedros007/mapserver-tindex-problem/blob/master/gray.png?raw=true
<https://github.com/pedros007/mapserver-tindex-problem/blob/master/gray.png?raw=true>
I have a
tileindex http://bl.ocks.org/d/968e0f11f1fd9b02444c3765bbb285a1
<http://bl.ocks.org/d/968e0f11f1fd9b02444c3765bbb285a1> that
basically stacks/flattens the black image on top of the gray
one. However, when I make a WMS request to the layer:
LAYER
NAME my_layer
TYPE RASTER
TILEINDEX tindex.shp
TILEITEM "location"
OFFSITE 0 0 0
STATUS OFF
END
END
I get only the gray image. In other words, I expected to get this:
https://github.com/pedros007/mapserver-tindex-problem/blob/master/expected.png?raw=true
<https://github.com/pedros007/mapserver-tindex-problem/blob/master/expected.png?raw=true>
but instead I get this:
https://github.com/pedros007/mapserver-tindex-problem/blob/master/gray.png?raw=true
<https://github.com/pedros007/mapserver-tindex-problem/blob/master/gray.png?raw=true>
I have a couple of work-arounds that I'm not crazy about:
1. Add Layer masks
http://www.mapserver.org/development/rfc/ms-rfc-79.html
<http://www.mapserver.org/development/rfc/ms-rfc-79.html> to two
separate layers, make two WMS requests and stack the results
client side. I have gotten this working for two layers. However,
I may need to render a very large number of such layers and
think this wont work client-side (via OpenLayers-3).
2. I could burn in NODATA values (or use a mask) to gray.tif,
but I'd rather not modify my source data.
A version of this email & example files are in a GitHub
repo: https://github.com/pedros007/mapserver-tindex-problem
<https://github.com/pedros007/mapserver-tindex-problem>
--
Pete
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--
Pete
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