On Aug 28, 9:26 pm, Paul Kulchenko <[email protected]> wrote:
> I'm writing visualization using canvas and would like to align my
> canvas objects with map tiles. Right now I'm using GTileLayer and
> toDataUrl to generate data: URLs and everything works fine.
> Unfortunately, one of my target platforms doesn't support toDataUrl,
> so I need to find some other mechanism.
>
> I'm considering generating one canvas per tile and the problem is with
> aligning my elements with the tiles; every generated image has this
> style:
>
> <img style="border: 0px none ; margin: 0px; padding: 0px; position:
> absolute; left: 315px; top: -149px; width: 256px; height: 256px; -moz-
> user-select: none; opacity: 0.5;"
>
> I'm after these "left: 315px; top: -149px;" coordinates to position my
> object in exactly the same way as this particular tile. Is there a way
> to find the image for a tile (its DOM object) based on having tile.x,
> tile.y and zoom information without doing brute force scanning of
> "map" element children searching for images with the right src value?
>
> Also these coordinates seem to change when the map is moved (not with
> every move, but when new tiles are loaded). I can probably have
> DOMListener to handle that, but the same question remains: how do I
> find what new coordinates are assigned to the tile that my particular
> div/canvas is covering?
>
> Is there a better way to align my elements with tiles? I wish there
> was a getTileDiv as there is getTileURL.
>
> Paul.
Some V3 examples of tile aligned CANVAS elements constructed on the
fly:
Simple
14,000 vertices
www.polyarc.us/polycluster/alaska.html
41,000 vertices
www.polyarc.us/polycluster/absurd.html
Advanced
20,000 vertices
www.polyarc.us/polycluster/canada.html
110,000 vertices
www.polyarc.us/polycluster
Similar arithmetic with less optimization can be found in the
following:
www.polyarc.us/sparsetile.js
It does not handle the International Date Line cross over correctly.
I believe
www.polyarc.us/polycluster.js
compensates correctly.
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