[gdal-dev] New OGR driver: Imageset

[Andreas Neumann]

 Hi,

 I agree that such a provider would probably slow - too slow for a 
 server, unless the data is cached somewhere (e.g. sqlite) and ogr only 
 reads new/updated files, and the rest from the cache.

 On the other hand it would still be useful for conversion into other 
 formats, where speed perhaps doesn't matter that much.

 Andreas

 On Mon, 23 Jul 2012 11:26:31 -0400, Daniel Morissette wrote:
> If I understand correctly, in the Open() call, this driver would open
> each image file to read its EXIF info and index the files in memory?
> This would work fine with a dozen images, but as the number of images
> increases the performance will suffer a lot and this would become
> unusable in apps such as MapServer, and even for Desktop apps with
> hundreds of images.
>
> If I needed this kind of functionality myself I would use a script to
> create an OGR point file as suggested by Even, to avoid the overhead
> caused by opening all the images.
>
> My 0.02$
>
> Daniel
>
>
> On 12-07-23 5:27 AM, Tamas Szekeres wrote:
>> Hi Even,
>>
>> I just want to use the directory name to define the connection to 
>> the
>> images, we could also provide to scan the files in subdirectories if
>> needed. I would prefer to have a new driver not just an offline tool 
>> for
>> creating OGR datasets, in this case many existing applications (like
>> MapServer) would be capable to utilize this feature.
>> I could imagine a driver configuration file to specify which driver
>> should be used for a particular image format and where the specific
>> information is located, I don't require to harmonize the metadata
>> structure at this time. We should probably allow mixing jpegs and 
>> tiffs
>> in the same directory, but the configuration should specify how the
>> similar attributes are provided by each (sub)driver.
>>
>> Best regards,
>>
>> Tamas
>>
>>
>>
>> 2012/7/23 Even Rouault <even.rouault at mines-paris.org
>> <mailto:even.rouault at mines-paris.org>>
>>
>>     Le lundi 23 juillet 2012 09:51:14, Tamas Szekeres a écrit :
>>      > Hi All,
>>      >
>>      > We're thinking about implementing a new OGR driver which 
>> would
>>     represent a
>>      > set of images as a vector data source. The images are taken 
>> from
>>     any GPS
>>      > compatible mobile device, and each picture would be 
>> represented
>>     as a point
>>      > feature, the positions would be extracted from the exif
>>     information. The
>>      > file name and path would be provided as an attribute for each
>>     feature. This
>>      > data source could then be used by higher level apps to 
>> provide
>>     symbols at
>>      > the picture locations in the map and display the picture when 
>> the
>>     feature
>>      > is selected. The driver would definitely use GDAL to extract
>>     information
>>      > about the provided images.
>>      >
>>      > I'm not sure whether we already have some kind of alternative
>>     solution to
>>      > this, let me know if you know about any. Further ideas about 
>> this
>>     topic
>>      > would also be helpful.
>>
>>     The JPEG driver already exposes EXIF information if found :
>>
>>     $ gdalinfo ../autotest/gdrivers/data/albania.jpg
>>     Driver: JPEG/JPEG JFIF
>>     Files: ../autotest/gdrivers/data/albania.jpg
>>     Size is 361, 260
>>     Coordinate System is `'
>>     Metadata:
>>     [...]
>>        EXIF_GPSLatitude=(41) (1) (22.91)
>>        EXIF_GPSLatitudeRef=N
>>        EXIF_GPSLongitude=(19) (55) (42.35)
>>        EXIF_GPSLongitudeRef=E
>>     [...]
>>
>>     $ gdalinfo ../autotest/gcore/data/exif_and_gps.tif -mdd EXIF
>>     Driver: GTiff/GeoTIFF
>>     Files: ../autotest/gcore/data/exif_and_gps.tif
>>     Size is 1, 1
>>     Coordinate System is `'
>>     [..]
>>     Metadata (EXIF):
>>     [...]
>>        EXIF_GPSLatitude=(77) (5) (60)
>>        EXIF_GPSLatitudeRef=S
>>        EXIF_GPSLongitude=(34) (12) (0)
>>        EXIF_GPSLongitudeRef=E
>>     [..]
>>
>>     Are you thinking to other raster formats to extract EXIF info 
>> from?
>>     To my
>>     knowledge, the JPEG driver, and recently the GTiff driver, are 
>> the
>>     only one
>>     that extract EXIF for now. I see that the JPEG driver exposes it 
>> in the
>>     default metadata domain, whereas I chose EXIF for the GTiff 
>> driver.
>>     For GTiff,
>>     the specific EXIF metadata domain seemed better to me to avoid
>>     'polluting' the
>>     default metadata domain, but I didn't want to change the JPEG 
>> driver
>>     at that
>>     point. But this would probably requires some harmonization.
>>
>>     So with some scripting, you could create for example a point
>>     shapefile, with
>>     the filename as attribute and GPS position as geometry.
>>
>>     In its syntax, this could be something similar to gdaltindex.
>>
>>     Doing that as a OGR driver would be also doable of course. The 
>> only
>>     point to
>>     solve is the definition of the connexion string to specify the 
>> image
>>     set.
>>
>>      >
>>      > Best regards,
>>      >
>>      > Tamas
>>
>>
>>
>>
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 Andreas Neumann
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