[gdal-dev] JPEG format.

[Belaid MOA]

Special thanks Even. You are always quick and to the point! Thank you very much. 
As you pointed out, I was handling JPEG in the same manner as GTiff; I did not use the MEM driver first. 

With best regards.
~Belaid.

> From: even.rouault at mines-paris.org
> To: gdal-dev at lists.osgeo.org
> Subject: Re: [gdal-dev] JPEG format.
> Date: Wed, 29 Jul 2009 19:55:46 +0200
> CC: belaid_moa at hotmail.com
> 
> Le Wednesday 29 July 2009 19:44:41 Belaid MOA, vous avez écrit :
> > Hi Everyone,
> >   When I try to use GDALCreate() on the JPEG driver, I got the following
> > error: "GDALDriver::Create() ... no create method implemented for this
> > format." Does is this mean that JPEG driver does not have its GDALCreate()
> > function implemented?
> 
> Hum, I can admit that sometimes error messages are not particularly clear, but 
> here .... !
> 
> > Any example on how to use JPEG driver is appreciated. 
> 
> The JPEG is no different from other drivers. The fact that the Create() method 
> is not implemented just reflect the fact that you can't write data at random 
> scanlines in a JPEG file, it must be created scanline by scanline, from top 
> to bottom. So you want to use the CreateCopy() method instead. As a source 
> raster for the CreateCopy(), you can use a dataset created with the MEM 
> driver (that supports the Create() method), or any other disk-based format 
> like GTIFF that supports the Create() method.
> 
> Schematically (in Python) :
> 
> mem_ds = gdal.GetDriverByName('MEM').Create(....)
> mem_ds.WriteRaster(....)
> 
> jpeg_ds = gdal.GetDriverByName('JPEG').CreateCopy(mem_ds, "out.jpg")
> jpeg_ds = None
> mem_ds = None
> 
> >
> >   As always, any help on this is very appreciated.
> >
> > With best regards.
> > ~Belaid
> >
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