[OpenLayers-Users] First try with html5 canvas for layers

[Kris Geusebroek]

Hi Eric,

I haven't measured the memory use yet. But I'm implementing the
tilecache layer with a single canvas, all images are loaded through a
javascript Image object and when all are loaded they are 'drawn' in the
single canvas. This way the number of dom elements is significantly
lower.

Thanks for the hint on the protocol. When I'm ready to implement that I
will sure have a look into the protocol types that are around.

Cheers Kris

-----Original Message-----
From: Eric Lemoine [mailto:eric.lemoine at camptocamp.com] 
Sent: Monday, November 23, 2009 7:44 AM
To: Kris Geusebroek
Cc: OpenLayers Users
Subject: Re: [OpenLayers-Users] First try with html5 canvas for layers

On Thursday, November 19, 2009, Kris Geusebroek <kgeusebroek at xebia.com>
wrote:
> Hi Eric,

Hi Kris. Thanks for response.

>
> Indeed it's cool, thanks.
> My goal was to write an application with open source technologies to
> track cars driving around.
> I wrote a prototype with geoserver and openlayers and this was
> succesfull. The big problem was the memory consumption (especially in
> IE) because of the large amount of DOM manipulation that is done when
> panning and zooming

do you manage to actually lower memory consumption with your
Canvas-based tiles? IIRC an image tile is two DOM elements (a div and
an img). How many elements is a Canvas tile? One?

> and drawing vector's (the cars, with fills, stroke,
> label etc.)
>
> Since using a plugin is out of the question here I began investigating
> the html5 canvas.
> I know it's not supported in IE, but for me that was a good thing
> because it gave me the opportunity to have the client choose a
different
> browser then IE.
>
> My plans for the future of the app is to also use workers and the
> browser database (to be able to store historical responses clientside
to
> draw a route the car has followed for the last 10 minutes or so)

This could be written as a OpenLayers.Protocol. Chris Schmidt started
an HTML5 Protocol a while back if I recall correctly. You may want to
check this with him.

Thanks,

-- 
Eric Lemoine

Camptocamp France SAS
Savoie Technolac, BP 352
73377 Le Bourget du Lac, Cedex

Tel : 00 33 4 79 44 44 96
Mail : eric.lemoine at camptocamp.com
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