Computer Graphics with Photoshop

Author

PSD compression

DLPnet

2004-05-18, 7:28 pm

Hello All,

I m developping a software to create PSD files but I would like to
compress the images (each layer). For the moment I m using RLE (packbit)
compression and everything is working well. But when working with 16
bits I cannot use anymore this compression and I would like also to
improve the compression factor.

Anyone knows any other compression scheme that PSD file format supports
? (LZW ? other ?)
And event better do you have an URL with such examples ?

Thanks a lot,

dlp

Bart van der Wolf

2004-05-18, 7:28 pm

"DLPnet" <dlpnet-@-free.fr> wrote in message
news:40a88ae6$0$22118$636a15ce@news.free.fr...
> Hello All,
>
>
> I m developping a software to create PSD files but I would like to
> compress the images (each layer). For the moment I m using RLE (packbit)
> compression and everything is working well. But when working with 16
> bits I cannot use anymore this compression and I would like also to
> improve the compression factor.

Just a word of caution; If you try to compress 16-b/ch continuous tone
images, there may be little gain and the file may even grow in size. The
reason is that there is a reduced chance of recurring bit patterns in those
images (esp. film scans) but dictionaries still need to be built.

> Anyone knows any other compression scheme that PSD file format supports
> ? (LZW ? other ?)
> And event better do you have an URL with such examples ?

Athough not PSD, you may still benefit from some of the info here:
http://www.libtiff.org/
http://home.earthlink.net/~ritter/tiff/

Also not that some forms of compression are not universally supported.

Bart

Chris Cox

2004-05-23, 12:08 pm

You will need to get the Photoshop SDK for that information.

Chris

In article <40a88ae6$0$22118$636a15ce@news.free.fr>, DLPnet
<dlpnet-@-free.fr> wrote:

> Hello All,
>
>
> I m developping a software to create PSD files but I would like to
> compress the images (each layer). For the moment I m using RLE (packbit)
> compression and everything is working well. But when working with 16
> bits I cannot use anymore this compression and I would like also to
> improve the compression factor.
>
> Anyone knows any other compression scheme that PSD file format supports
> ? (LZW ? other ?)
> And event better do you have an URL with such examples ?
>
> Thanks a lot,
>
> dlp

DLPnet

2004-05-25, 7:14 pm

Hello Chris,

[color=darkred]
> You will need to get the Photoshop SDK for that information.

I have it ! Can you tell me where to look for this information. I didn t
find anything on this topic.

Thanks a lot,

Dlp

Chris Cox

2004-05-29, 11:14 pm

In article <40b36bc0$0$6355$626a14ce@news.free.fr>, DLPnet
<dlpnet-@-free.fr> wrote:

> Hello Chris,
>
>
>
>
> I have it ! Can you tell me where to look for this information. I didn t
> find anything on this topic.

That would be in the document on Photoshop file formats.
But for Photoshop 7 and later, you have to specifically request the
file format documentation.

CHris