looks like a good idea to me
Ian
On Wed Jan 28 2015 at 1:46:08 PM Andrea Aime <andrea.a...@geo-solutions.it>
wrote:
> Hi,
> I am looking into making the GeoTools rendering subsystem more useful
> in a set of maps with legal value where the label positioning has a number
> of rules that need to be respected, including linear and polygonal
> obstacles,
> use of leader lines, and the requirement that all labels must be present
> in the
> map, no matter what, pushing us to add a number of extra options to make
> this possible, including accepting label overlap if all other options are
> exhausted.
>
> The amount of changes is large... I'm going to add it all in this mail
> using HTML
> so give it a bit of structure, but let me know if you prefer a PDF
> attachment instead.
>
>
> -------------------------------------------------------------------------------------------------------------
>
> New modified/vendor options leader
>
> This option will activate the usage of a leader line in case the label was
> moved away from its original position. It will play along with
> maxDisplacement, which currently allows the label to move away from the
> label point without one, and will take into account the leader line itself
> to make sure it does not overlap with other labels.
>
>
> Default leader line:
>
> <VendorOption name=”leader”>true</VendorOption>
>
> Black leader line, 3 px wide:
>
> <VendorOption name=”leader”>#000000,3</VendorOption>
>
>
> In case of polygons, the leader line will be painted only if the label
> does not overlap the polygon.
> labelObstacle
>
> The current label obstacle vendor option acts by marking the bounding box
> of the obstacle as an obstacle for the labels. This will be modified to use
> the actual geometry, plus a buffer to take into account the size of the
> symbolizer.
>
>
> Moreover, obstacles will be classified as obstacles for labels only, and
> obstacles for labels and leader lines, defaulting as objstacles for labels
> only. The rationale is that we might not want the labels to overlap with
> some linework, but it’s ok to have the leader line cross it (this is
> especially true if we don’t want polygon labels to cross the polygon
> border, but the leader line pointing to a label outside the polygon has no
> choice but cross)
>
>
> Obstacle for labels only:
>
> <VendorOption name=”labelObstacle”>labelsOnly</VendorOption>
>
> Obstacle for labels and leader lines only (backwards compatible setting):
>
> <VendorOption name=”labelObstacle”>true</VendorOption>
>
> <VendorOption name=”labelObstacle”>leaderLabels</VendorOption>
>
>
> This will require a classification of obstacles in the label cache and
> conflict engine.
> autoReduce
>
> The new autoReduce vendor option will allow the renderer to reduce the
> size of labels up to a certain percentage, with an optional step (default
> step reduction value, 10%).
>
>
> Examples (reduce down to 50%px, down to 50% with steps of 25%)
>
> <VendorOption name=”autoReduce”>0.5</VendorOption>
>
> <VendorOption name=”autoReduce”>0.5,0.25</VendorOption>
>
>
> autoGoodnessOfFit
>
> This option will allow the labeller to reduce the goodness of fit for
> polygon labels, allowing the label to gradually move out of the polygon,
> with an optional reduction step (10% by default)
>
>
> Examples (reduce gof to 0 in steps of 10%, reduce gof to 0 in steps of
> 25%):
>
> <VendorOption name=”autoGoodnessOfFit”>0</VendorOption>
>
> <VendorOption name=”autoGoodnessOfFit”>0,0.25</VendorOption>
> alterationOrder
>
> When all the label movement options are set on points and polygons, they
> are applied in the following order:
>
> 1.
>
> Simple movement without rotation
> 2.
>
> Polygon align (ortho, mbr, and go back to step one, moving)
> 3.
>
> Scale font (and go back to step one, moving and rotating)
> 4.
>
> Goodness of fit reduction
>
>
> A new vendor option, alterationOrder, will be used to control in which
> order the attempts are made:
>
> <VendorOption
> name=”alterationOrder”>maxDisplacement,polygonAlign,autoReduce,autoGoodnessOfFit</VendorOption>
> force
>
> When set to true, will force a label to be painted regardless of overlaps,
> in the position tested so far that has the least overlap with other labels
> and obstacles.
>
>
> Significant changes to LabelCacheImpl
>
> The internal works of LabelCacheImpl will be modified to allow the label
> position/charactesitics alteration in a pluggable system. Each alteration
> will be a ItemModifier, which generates an iteration of LabelCacheItem with
> some bits being modified:
>
>
> public interface ItemModifier {
>
> Iterator<LabelCacheItem> modify(LabelCacheItem item);
>
> }
>
>
> At each step in the iterator the modifier will attempt a different
> modification, returning a deep clone of the originalLabelCacheItem. The
> first modification will be however exactly the cache item provided in the
> modify method (first step is “no modification”).
>
>
> The label cache item will then feed the modified item to the next
> modified in the chain, until all possible combination of modifications are
> tested.This can be of course very expensive, depending on the number of
> label combinations attempted, so the stop flag will be checked during the
> iterations, and not only between one label and the next one.
>
>
> In order to support the new label obstacle requirements the LabelCache
> interface will be modified to allow using a geometry plus an eventual
> buffer, and the type of obstable:
>
>
> enume ObstacleType {FULL, LABEL};
>
>
> LabelCache.put(Geometry g, int distancePixels, ObstacleType type);
>
>
> In order to satisfy the requirements of the “force” option a quick way
> to compute the overlap area is required, compounded with the need to check
> two different types of overlap, and the desire to check two different types
> of overlap, will require the LabelIndex class to be re-implemented using a
> raster based approach:
>
> -
>
> Two black and white mask images, one for pure leader line obstacles,
> one for full obstacles
> -
>
> The label bounding rectangle will be tested against these two images
> for conflicts, and eventualy painted to the full obstacles one in case
> there is no conflict
> -
>
> In case the label bounding rectangle is not aligned to the axis, it
> will be painted to a third black and white image to identify which pixels
> fall inside the area of interest
> -
>
> As a memory optimization, the target masks will be split into smaller
> tiles that are not allocated in memory when fully empty or fully busy
>
>
> -------------------------------------------------------------------------------------------------------------------------
>
> If you're wondering why this is not a proposal, it's because the funding
> is not secured yet
> (which is the main point of proposals, make sure there is full resourcing
> to carry it out).
> Of course, this would be scheduled for 14.x
>
> Feedback welcomed!
>
> Cheers
> Andrea
>
> --
> ==
> GeoServer Professional Services from the experts! Visit
> http://goo.gl/NWWaa2 for more information.
> ==
>
> Ing. Andrea Aime
> @geowolf
> Technical Lead
>
> GeoSolutions S.A.S.
> Via Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
> phone: +39 0584 962313
> fax: +39 0584 1660272
> mob: +39 339 8844549
>
> http://www.geo-solutions.it
> http://twitter.com/geosolutions_it
>
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Dive into the World of Parallel Programming. The Go Parallel Website,
sponsored by Intel and developed in partnership with Slashdot Media, is your
hub for all things parallel software development, from weekly thought
leadership blogs to news, videos, case studies, tutorials and more. Take a
look and join the conversation now. http://goparallel.sourceforge.net/
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