jpeg package: wrong jpeglib.h?

Charles Wilson
Wed Sep 3 05:11:00 GMT 2003

Teun Burgers wrote:

> I've got a program that won't compile with /usr/include/jpeglib.h.
> The reason is that struct jpeg_component_info does
> not contain height_in_blocks.
> The jpeglib.h distributed in jpegsrc.v6b.tar.gz from
> *does* contains height_in_blocks.
> What is the reason for using a different jpeglib.h?

Cygwin's jpeg is built with the lossless jpeg patch, which modifies the 
header files slightly.  However, if you read the header file carefully, 
height_in_blocks is in the PRIVATE section of the header.  It is NOT 
supposed to be accessed by external programs -- I have this on the 
highest (for jpeg) authority, Tom Lane himself.

So, don't do that.

But, if you must do that, height_in_blocks has simply been renamed to 
"height_in_data_units" -- because with lossless jpeg, each "compression 
unit" is not necessarily a DCT block.

Please search the mailing list archives where this has been discussed in 
the past. IIRC several mechanisms for working transparently with the 
cygwin versions of the jpeglib headers were presented in those discussions.


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