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

[Frank Warmerdam]

Ethan,

It only happens if there appears to be a valid mask on the source
image that gets copied by gdal_translate in a CreateCopy() call to the
jpeg driver.  There are various reasons a source might or might not
have a mask.

Best regards,
Frank

On Fri, Apr 13, 2012 at 2:31 PM, Ethan Alpert <ealpert at digitalglobe.com> wrote:
> 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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