[gdal-dev] Problem with garbage bytes of data after EOI marker in single band JPEG

[Ethan Alpert]

Ok why does this not happen with multi band jpgs?

 

From: Even Rouault [mailto:even.rouault at mines-paris.org] 
Sent: Friday, April 13, 2012 1:13 PM
To: gdal-dev at lists.osgeo.org
Cc: Ethan Alpert
Subject: Re: [gdal-dev] Problem with garbage bytes of data after EOI marker in single band JPEG

 

Le vendredi 13 avril 2012 19:53:41, Ethan Alpert a écrit :

> 

> This has been running for years. Recently a customer who receives these

> started scanning the JPG's for security threats. Turns out that the

> JPG's I've been writing have garbage data after the JPEG EOI marker.

> 

This is not garbage, but mask data appended after the JPEG data stream, as documented in the JPEG driver doc : 

"""The driver also supports the "zlib compressed mask appended to the file" 

approach used by a few data providers to add a bitmask to identify pixels that 

are not valid data."""

The mask is due to the advertized nodata value in the VRT. You can likely remove it by adding <HideNoDataValue>1</HideNoDataValue> in the VRT file under the VRTRasterBand element.


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