[gdal-dev] New OGR driver: Imageset

[Daniel Morissette]

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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-- 
Daniel Morissette
http://www.mapgears.com/
Provider of Professional MapServer Support since 2000