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Posted to fop-users@xmlgraphics.apache.org by Ben Galbraith <bg...@amirsys.com> on 2003/07/07 20:03:08 UTC
Website update?
I believe the FOP website lurks on this list, right?
I have done some further research on exactly what image support FOP
offers, in efforts to figure out how to embed CMYK images into a
resultant PDF. Perhaps this information will be of use to others.
Here's what I've found:
Native TIFF
- only supports 1 sample per pixel images
- only supports "white-is-zero" and RGB photometric interpretation
(although due to the sample per pixel limitation above, RGB images are
unsupported)
- appears to support the following compression schemes:
- CCITT T.4 bi-level encoding
- CCITT T.6 bi-level encoding
- JPEG compression
JAI TIFF
- images MUST be RGB
- RGBA appears to be supported to some degree
- all other support should be consistent with JAI
JAI PNG
- images MUST be RGB
- RGBA appears to be supported to some degree
- all other support should be consistent with JAI
Native JPG
- grayscale, RGB, and CMYK appear to be supported
Native BMP
- images must be RGB
I can provide more granular information if necessary. As a result of my
findings, it is clear that for embedding CMYK images into a resultant
PDF, JPG is the only game in town.
Ben
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Re: Website update?
Posted by Ben Galbraith <bg...@amirsys.com>.
Victor Mote wrote:
> Got it. Thanks. As I am writing this up, I wonder whether the FOP native
> support handles uncompressed images as well? Do you know?
Yep! Uncompressed images are supported by FOP native.
Ben
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RE: Website update?
Posted by Victor Mote <vi...@outfitr.com>.
Ben Galbraith wrote:
> So the final text
> could probably be reduced to:
>
> "FOP's native support for TIFF's is limited to single channel images
> (i.e., bi-level and grayscale). Said images must use CCITT T.4, CCITT
> T.6, or JPEG compression, and must use white-is-zero encoding (TIFF's
> 'photometric interpretation' field)."
Got it. Thanks. As I am writing this up, I wonder whether the FOP native
support handles uncompressed images as well? Do you know?
Victor Mote
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Re: Website update?
Posted by Ben Galbraith <bg...@amirsys.com>.
Victor Mote wrote:
> I'm no expert here, but I waded through the TIFF spec a bit, and offer the
> following paraphrase, which I ask you to either confirm or deny:
> <paraphrase>What TIFF calls sample-per-pixel is the number of channels. So
> WhiteIsZero can support bi-level and grayscale images through that one
> channel. But RGB photometric interpretation needs at least three channels,
> and only has 1 to work with, therefore no color. RGB Palette could use that
> one channel for a 256-color palette, but it is unsupported. So the bottom
> line is that FOP native can't support color TIFF images at all, RGB or
> otherwise.</paraphrase>
RE: Sample per pixel versus number of channels. That's right. AFAIK,
the terms "channels", "bands", and "samples per pixel" are all synonymous.
RE: Photometric interpretation. I think I may have exposed a level of
detail that makes this more complicated than it needs to be. The code
in FOP supports values for the photometric interpretation field of 0 and
2, which translates to WhiteIsZero and RGB. However, since only one
band/channel is supported, the fact that the code doesn't bail on a
photometric interpretation value of 2 is just a bug. So the final text
could probably be reduced to:
"FOP's native support for TIFF's is limited to single channel images
(i.e., bi-level and grayscale). Said images must use CCITT T.4, CCITT
T.6, or JPEG compression, and must use white-is-zero encoding (TIFF's
'photometric interpretation' field)."
> The rest of this I follow, and will make changes to the website accordingly.
> Again, thanks for your efforts here.
It's my pleasure to contribute some small amount to a project that has
proved immensely valuable to me. :-)
Ben
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RE: Website update?
Posted by Victor Mote <vi...@outfitr.com>.
Ben Galbraith wrote:
> I believe the FOP website lurks on this list, right?
Most of the developers help maintain the content, but I have probably been
most heavily involved with doc in recent days.
> I have done some further research on exactly what image support FOP
> offers, in efforts to figure out how to embed CMYK images into a
> resultant PDF. Perhaps this information will be of use to others.
Thanks very much for documenting all of this. I wish we had the resources to
just go fix all of this, but the next best thing is to document it.
> Here's what I've found:
>
> Native TIFF
> - only supports 1 sample per pixel images
> - only supports "white-is-zero" and RGB photometric interpretation
> (although due to the sample per pixel limitation above, RGB images are
> unsupported)\
I'm no expert here, but I waded through the TIFF spec a bit, and offer the
following paraphrase, which I ask you to either confirm or deny:
<paraphrase>What TIFF calls sample-per-pixel is the number of channels. So
WhiteIsZero can support bi-level and grayscale images through that one
channel. But RGB photometric interpretation needs at least three channels,
and only has 1 to work with, therefore no color. RGB Palette could use that
one channel for a 256-color palette, but it is unsupported. So the bottom
line is that FOP native can't support color TIFF images at all, RGB or
otherwise.</paraphrase>
> - appears to support the following compression schemes:
> - CCITT T.4 bi-level encoding
> - CCITT T.6 bi-level encoding
> - JPEG compression
>
> JAI TIFF
> - images MUST be RGB
> - RGBA appears to be supported to some degree
> - all other support should be consistent with JAI
>
> JAI PNG
> - images MUST be RGB
> - RGBA appears to be supported to some degree
> - all other support should be consistent with JAI
>
> Native JPG
> - grayscale, RGB, and CMYK appear to be supported
>
> Native BMP
> - images must be RGB
>
> I can provide more granular information if necessary. As a result of my
> findings, it is clear that for embedding CMYK images into a resultant
> PDF, JPG is the only game in town.
The rest of this I follow, and will make changes to the website accordingly.
Again, thanks for your efforts here.
Victor Mote
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