[OpenLayers-Users] Zoomify and fractional zoom

Andreas Hocevar ahocevar at opengeo.org
Wed Jun 27 07:25:07 PDT 2012 

This sounds sane at first glance. If you can send a pull request with
this patch, it will be easier to verify if tests still pass and
examples still work.

Thanks,
Andreas.

On Wed, Jun 27, 2012 at 4:15 PM, David Régade <dregade at viewsurf.com> wrote:
> Ok, it works now.
>
> To do that I configured my layer's serverResolutions with the same array I
> set up for resolutions.
> Only with this trick tiles are not correctly displayed because Zoomify
> functions getURL and getImageSize use:
>
> var res = this.map.getResolution();
> ...
> var z = this.map.getZoom();
>
> instead of:
>
> var res = this.getServerResolution();
> ...
> var z = this.getZoomForResolution( res );
>
>
> With this patch and layer correct configuration, fractionalZoom works for me
> with Zoomify layer.
>
> Do you think this patch is correct or should I take care of some specials
> cases ?
>
> Regards
> David
>
>
> On 27/06/2012 15:00, Andreas Hocevar wrote:
>>
>> To achieve this, it should be enough to configure your layer's
>> serverResolutions with the same array that you have set for
>> resolutions.
>>
>> Andreas.
>>
>> On Wed, Jun 27, 2012 at 2:46 PM, David Régade<dregade at viewsurf.com>
>>  wrote:
>>>
>>> I tried this solution too and it didn't work. I had a look to this
>>> example:
>>>
>>> http://openlayers.org/dev/examples/fractional-zoom.html
>>>
>>> In this example tile size is allways 256x256 whatever the zoom level. But
>>> with zoomify it can't be allways 256x256 because tiles have to be
>>> streched
>>> or shrinked according to zoom level. zoomify relies on direct tile image
>>> url
>>> , not a mapserver like the example above. These direct images urls have
>>> fixed dimensions and represent allways the same "world region".
>>> That's why I can't figure out fractionalZoom can work with Zoomify layer
>>> if
>>> the displayed tile have allways the same size.
>>>
>>> A solution could be to setup the integer zoom for the layer and scale the
>>> layer (like transformDiv() does) to obtain the good result.
>>>
>>> Regards
>>> David
>>>
>>>
>>> On 27/06/2012 12:12, Andreas Hocevar wrote:
>>>>
>>>>
>>>> I see. So maybe you need to leave the original z assignement as-is
>>>> (without Math.round or Math.floor), and only change the lines that say
>>>>
>>>> this.tierSizeInTiles[z]
>>>>
>>>> to something like
>>>>
>>>> this.tierSizeInTiles[z|0]
>>>>
>>>> (z|0 being a more efficient way of saying Math.floor(z)).
>>>>
>>>> Andreas.
>>>>
>>>> On Wed, Jun 27, 2012 at 12:04 PM, David Régade<dregade at viewsurf.com>
>>>>  wrote:
>>>>>
>>>>>
>>>>> I tried Math.floor and the problem is the same. I'm not sure the
>>>>> problem
>>>>> comes from Math.round/floor because with my example, for an integer
>>>>> zoom
>>>>> value (3 for example), top left displayed tile is 256px width (thanks
>>>>> firebug). For a 3.4 zoom value should the top left tile image width be
>>>>> greater than 256px ?
>>>>>
>>>>> So if the displayed tile images are 256px for 3.4 zoom level, you need
>>>>> more
>>>>> tile to cover the layer extent in resolution associated to this zoom
>>>>> level.
>>>>> That's why on my axample, when you click on the button the displayed
>>>>> tile
>>>>> images are not centered as is it should be and another image tile (that
>>>>> doesn't exist) is required and tried to be drawn. Am I wrong ?
>>>>>
>>>>> Here is a screenshot of what I observed:
>>>>> http://david.regade.free.fr/openlayers/z3.4.jpg
>>>>>
>>>>> Regards
>>>>> David
>>>>>
>>>>>
>>>>> On 27/06/2012 11:41, Andreas Hocevar wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> Try Math.floor instead of Math.round - currently the client zoom
>>>>>> implementation only supports oversampling, so you need the next
>>>>>> smallest zoom level.
>>>>>>
>>>>>> Andreas.
>>>>>>
>>>>>> On Wed, Jun 27, 2012 at 10:51 AM, David Régade<dregade at viewsurf.com>
>>>>>>  wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> It can't be so easy. I fixed line 225 with:
>>>>>>>             var z = Math.round(this.map.getZoom());
>>>>>>>
>>>>>>> And another bug appeared line 201, same fix:
>>>>>>>             var z = Math.round(this.map.getZoom());
>>>>>>>
>>>>>>> However on this example, http://david.regade.free.fr/openlayers/,
>>>>>>> setting
>>>>>>> zoom to 3.4 doesn't generate javascript errors anymore but the result
>>>>>>> isn't
>>>>>>> correct. A tile is tried to be drawn and it shouldn't.
>>>>>>>
>>>>>>> I tried to trace where and why this tile is drawn but I'm to new to
>>>>>>> openlayers to find where the problem comes from.
>>>>>>>
>>>>>>> Regards
>>>>>>> David
>>>>>>>
>>>>>>> On 27/06/2012 08:05, Andreas Hocevar wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> I just see that there is a bug in Zoomify.js, line 225:
>>>>>>>>
>>>>>>>>             var z = this.map.getZoom();
>>>>>>>>
>>>>>>>> We need the integer of getZoom() here instead.
>>>>>>>>
>>>>>>>> Maybe you want to send a pull request with a fix?
>>>>>>>>
>>>>>>>> Andreas.
>>>>>>>>
>>>>>>>> On Tue, Jun 26, 2012 at 11:33 PM, David Régade<dregade at viewsurf.com>
>>>>>>>>  wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I get the last OpenLayers master and this feature doesn't work with
>>>>>>>>> the
>>>>>>>>> following example:
>>>>>>>>>
>>>>>>>>> http://david.regade.free.fr/openlayers/
>>>>>>>>>
>>>>>>>>> Is there something I'm doing wrong ?
>>>>>>>>>
>>>>>>>>> When setting up a fractional zoom (by clicking on the button for
>>>>>>>>> example)
>>>>>>>>> Firebug catches an error.
>>>>>>>>> Layer is resized but the tiles are not set correctly.
>>>>>>>>>
>>>>>>>>> David
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 26/06/2012 16:32, Andreas Hocevar wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> This is supported in OpenLayers master and the upcoming 2.12
>>>>>>>>>> release.
>>>>>>>>>>
>>>>>>>>>> Andreas.
>>>>>>>>>>
>>>>>>>>>> On Tue, Jun 26, 2012 at 3:12 PM, David
>>>>>>>>>> Régade<dregade at viewsurf.com>
>>>>>>>>>>  wrote:
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Hi,
>>>>>>>>>>> We use openlayers to display large panoramas. We use ZoomifyImage
>>>>>>>>>>> to
>>>>>>>>>>> split
>>>>>>>>>>> original image in tiles and Zoomify layer to display these tiles.
>>>>>>>>>>> I would like to use fractionalZoom with Zoomify layer but this
>>>>>>>>>>> layer
>>>>>>>>>>> doesn't
>>>>>>>>>>> support this feature. The main goal is to able to resize
>>>>>>>>>>> displayed
>>>>>>>>>>> tiles
>>>>>>>>>>> for
>>>>>>>>>>> zoom level 3 from 2.5 to 3.4.
>>>>>>>>>>>
>>>>>>>>>>> Does anyone knows how to do that ?
>>>>>>>>>>>
>>>>>>>>>>> Thanks in advance
>>>>>>>>>>> --
>>>>>>>>>>> David REGADE
>>>>>>>>>>> _______________________________________________
>>>>>>>>>>> Users mailing list
>>>>>>>>>>> Users at lists.osgeo.org
>>>>>>>>>>> http://lists.osgeo.org/mailman/listinfo/openlayers-users
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> Users mailing list
>>>>>>>>> Users at lists.osgeo.org
>>>>>>>>> http://lists.osgeo.org/mailman/listinfo/openlayers-users
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>>
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>>
>>
>>
>>
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-- 
Andreas Hocevar
OpenGeo - http://opengeo.org/
Expert service straight from the developers.

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