At 02:07 PM 3/7/2006, Petter Nyström wrote:
I hope this is correct. Writing these bytes to a
file will however not produce anything useful.
That is correct, in many cases.
Images in PDF files are either in
JPEG/JFIF format OR they are a raw "array of
pixels". In the first case, you can indeed just
"dump the data to disk" and get a usable
image. In the second, you will need to convert
it to some standard image format.
None of my image viewing program will understand
it. Neither would ppmtojpeg or a host of other
conversion programs that I've tried at it. :p
ImageMagick will understand it as a raw
bitmap format, if you provide the necesary
colorspace, etc. values. but that won't help your users.
So there I am. Reading the dictionary of the
PRStream I learn that the colorspace is of the
type /DeviceCMYK. And while I think I have a
(very) basic understanding of what that means, I
am far from ready to manipulate the byte stream
into a recognizable image format myself!
Yes, you have a LOT to learn to get from
a PDF image data to usuable image formats. You
need to learn about colorspaces (and conversion
thereof), bit depths, indexed vs. "true color", etc.
I feel I am moving outside the scope of iText here...
Somewhat, but as long as it is PDF
related we can help you for a bit...
But could someone give any pointers to what
tools that exist, both within and outside iText,
for dealing with a byte stream of this type? I
want this stream turned into some sort of standard image format to work with.
So you'll need the following components.
1) Image buffer management
2) Colorspace handling and/or conversion
3) File format writing
Are there other troubles I should watch out for?
Sure, a bunch.
Such as byte streams being encrypted, compressed, etc.?
Encryption is handled automatically by
iText - PROVIDED that you have the rights to
extract the data from the PDF. Remember, not all authors grant such rights.
Decompression will be handled by iText
as well - BUT you DO NOT want to do always do
it. Images compressed with DCTDecode (aka JPEG)
should be treated as UNCOMPRESSED.
Leonard
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Leonard Rosenthol <mailto:[EMAIL PROTECTED]>
Chief Technical Officer <http://www.pdfsages.com>
PDF Sages, Inc. 215-938-7080 (voice)
215-938-0880 (fax)
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