El 30/01/2013 12:01, silvioprog escribió:
ps. IMHO, this is wrong:
https://github.com/jepafi/Free-JPDF-Pascal/blob/master/libjpfpdf.pas#L1681.
He promises to support multiple images, but internally it converts them
all to JPEG, and this causes lose quality in some images.
PDF supports PNG natively, but need to implement the specification
exactly how Adobe explains. Two explains below:
For JPEG:
1 - DCTDecode a lossy filter based on the JPEG standard; (I implemented it)
For PNG:
1 - FlateDecode a commonly used filter based on the zlib/deflate
algorithm (a.k.a. gzip, but not zip) defined in RFC 1950 and RFC 1951;
introduced in PDF 1.2; it can use one of two groups of predictor
functions for more compact zlib/deflate compression: Predictor 2 from
the TIFF 6.0 specification and predictors (filters) from the PNG
specification (RFC 2083);
2 - LZWDecode a filter based on LZW Compression; it can use one of two
groups of predictor functions for more compact LZW compression:
Predictor 2 from the TIFF 6.0 specification and predictors (filters)
from the PNG specification;
Hello,
I'm working in a PDF rendering unit which currently can render very
basic PDFs (you know, some rects, no clipping, some texts...) so any
advance in any filter will be welcome. To generate the FlateDecode you
can use the "ztream" unit and the TCompressionStream class (with
ASkipHeader=false).
Simple PDFs that use filters and predictors will be welcomed also.
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