[Gdal-dev] two subjects - Katrina Good News and Request for VRT API
buckmasterjunior at yahoo.com
Wed Oct 5 21:17:35 EDT 2005
It's been a while since I've written to the list, and it seems as though I only write when necessity insists, but this time I have a good news story to share.
A few days after Katrina dissipated enough to fly relief photo missions into the hardest struck areas of Louisiana/Mississippi, nearly thousand images were collected by a National Guard platform. These images were processed with a VB6 utility that basically accomplishes all the georeferencing math based upon sensor model ephemeris, creates a world file and calls gdal_translate to compress large bitmaps into georeferenced jpeg2000 images. Since this GDAL-based utility was designed to process in batch mode, processing the raw imagery into exploitable data was quick, accurate and reliable. Based upon the feedback I received, at least a dozen residences with distress markings were identified and more importantly, located with decent enough coordinates to pass to dispatched rescue teams. The compression from 80+mb to 5mb files allowed timely transfer of the georeferenced imagery betwixt agencies in a bandwidth-constrained environment as well.
Ladies and gentlemen, it is my firm belief lives were saved as a result of the hard work dedicated to the open-source GDAL project. Frank, you and and the entire GDAL Development Team deserve a LOUD round of applause!
Now for the second subject: I need to create a version of the VB6 utility mentioned above that can be triggered by filecreate messaging - basically monitoring a directory for the create completion of a bitmap. With the VB6 binding now available, courtesy of Frank, this is also an opportunity to drop the gdal_translate functionality directly and cleanly into the utility...if VRT API VB binding is available, a missing link Frank pointed out in March. If anyone (with more skills than I) could take this on, I would be most grateful, as I'm sure other folks would be as well.
I know VB6 really isn't the development tool of choice anymore, but in my industry, it can be difficult receiving certification and accreditation to operate apps developed in .NET. There still is a niche for VB6 development, and I believe fleshing out GDAL associated APIs with VB6 bindings can lead to some great apps. I personally am not skilled enough to writing bindings, but I can sure use them in RAD prototypes.
PS - Frank, do you think there is enough interest to start a gdal-vb-dev mailing list?
On Thu, 17 Mar 2005 11:03:44 -0800 (PST), Gerald Buckmaster
<buckmasterjunior at yahoo.com> wrote:
> Good Stuff!
> I edited to provide a path for the GDAL library and the sample data -
> everything worked fine.
> I briefly looked over functions...were you able to include all GDAL
> Or at least all utilized by gdal_translate.exe? How difficult would
> for a VB6 version of gdal_translate to be written? Does the ECW
> SDK have VB6 bindings as well? This could be BIG!
The VB6 bindings are not comprehensive, though I think I have hit
most of the key items. The VB6 script I sent demonstrated the core
of gdal_translate functionality. But a complete implementation would
need access to the VRT API or else quite a bit of VB code to
create in-memory VRT documents. The VRT mechanism is used
for subsetting and band remapping in gdal_translate.
There are no VB6 ECW JPEG2000 SDK bindings that I am aware of,
but of course the VB6 GDAL bindings give access to that capability
within the data model limitations of GDAL.
I am personally quite excited by the VB6 bindings, but to be honest,
it seems there are a limited number of folks these days writing new
VB6 apps so I don't anticipate it having a huge impact on GDAL
usage. I am happy to make improvements to the VB6 bindings
though. Also, if you look through how I have done the bindings
you can quite easiily extend them for new calls without even
having to recompile GDAL. Most of my work on the bindings
(after the initial building hurdle) was just writing new Declare
statements for C API functions (in GDALCore.bas) and then
extending the Visual Basic classes to call into those low level
Yahoo! for Good
Click here to donate to the Hurricane Katrina relief effort.
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