how does one read image data in tiff file compressed by adobe enflate?
lazarus / 39-Graphics

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stab · 2017-08-17 18:30

Hi,

Can someone guide me on how to read image data in tiff file compressed
by adobe enflate?

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Mick · 2017-08-18 00:05

Hi, do you mean Adobe Deflate or maybe there is a new compression
scheme introduced into TIFF which I am not aware of?
Do you know what is the actual numeric value of the TIFF compression
tag for that image? If not, then you could try to use some kind TIFF-
info tool (there are a couple of them). For Adobe Deflate the
compression tag value should be 8. As far as I know it is just the
same  compression scheme as Deflate (with compression tag value of
32946).
If you don't know any tools, then you could post the TIFF file and I
can inspect it.

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Handoko · 2017-08-18 01:46

Maybe you can try to use:
http://wiki.freepascal.org/fcl-image

I used it on glSlideshow, tested with lots of sample images, no
problem so far:
https://forum.lazarus.freepascal.org/index.php/topic,35313.msg256719.h
tml#msg256719

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stab · 2017-08-18 11:40

Thanks for info Mick,

compression tag value = 8 and I suppose
I can use zlib to decompress then?

Regards
stab

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molly · 2017-08-18 12:17

Quote from: stab on August 18, 2017, 01:40:10 pmI can use zlib to
decompress then?
Forgive my ignorance but, why would you want to do do that manually ?

fcl image seems to support deflate (according to the wiki that user
Handoko linked to) so either using fcl-image or TTiffImage/TPicture
should be able to get you going.

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Mick · 2017-08-18 12:48

Quote from: stab on August 18, 2017, 01:40:10 pm...I can use zlib to
decompress then?...In theory - yes, but don't expect that you will be
able to feed the zlib decompressor with the data from TIFF, it is much
more complex than that. As already suggested by others, use fcl-image,
although it has some missing features, it works in most cases. In
other case you could go with some libtiff port (much more hassle,
though).