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List:       kde-core-devel
Subject:    [Fwd: Bug#1707: kimgio does not recognize every JPEG image]
From:       Harri Porten <porten () tu-harburg ! de>
Date:       1999-08-10 12:59:40
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Hi !

Should we relax the file magic check for JPEG images ? A 0xffd8 is
certainly good enough for indicating a JPEG file but what about
compatibility ? The README in the jpeg directory says:

> FILE FORMAT WARS
> ================
>
> Some JPEG programs produce files that are not compatible with our library.
> The root of the problem is that the ISO JPEG committee failed to specify a
> concrete file format.  Some vendors "filled in the blanks" on their own,
> creating proprietary formats that no one else could read. 
> [...]
> Various proprietary file formats incorporating JPEG compression also exist.
> We have little or no sympathy for the existence of these formats.  Indeed,
> one of the original reasons for developing this free software was to help
> force convergence on common, open format standards for JPEG files.  Don't
> use a proprietary file format!

So the question is

a) a political one (support proprietary formats ?)
b) a technical one (will the library handle these formats ?)

Harri.

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Subject: Bug#1707: kimgio does not recognize every JPEG image
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Package: kdelibs
Version: 1.1.1

The IO handler defined in kimgio.cpp does only regognize JFIF images,
since it uses the regular expression "^\377\330\377\340..JFIF".

It doesn't recognize pictures taken by Kodak digital kameras, for example,
which contain the bytes "\377\330\377\340..Exif" in the header.

The magic data file on Debian GNU/Linux systems uses only two bytes to
recognize JPEG images:

 # JPEG images
 # SunOS 5.5.1 had
 #
 #	0	string		\377\330\377\340	JPEG file
 #	0	string		\377\330\377\356	JPG file
 #
 # both of which turn into "JPEG image data" here.
 #
 0	beshort		0xffd8		JPEG image data
 >6	string		JFIF		\b, JFIF standard
 # HSI is Handmade Software's proprietary JPEG encoding scheme
 0	string		hsi1		JPEG image data, HSI proprietary

Therefore, I think, the regular expression "^\377\330\377\340..JFIF"
should be shortened to "^\377\330" in kimgio.cpp:

 #ifdef HAVE_LIBJPEG
	 // JPEG
	 QImageIO::defineIOHandler( "JPEG", "^\377\330", 0,
			 kimgio_jpeg_read, kimgio_jpeg_write );
 #endif

Or maybe to something a little bit more safe, like
"^\377\330\377...[A-Za-z][A-Za-z][A-Za-z][A-Za-z]".



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