> On 31 Mar 2016, at 12:40, John Hewson <[email protected]> wrote: > > > > -- John > On 30 Mar 2016, at 07:18, Costas Stergiou <[email protected]> wrote: > >>> PDF/A is for archiving, and while PDF/A-2 does support JPEG 2000, it's not >> a good choice for an archival format, because most JPEG 2000 implementations >> are broken in some way and many PDF viewers cannot correctly view such >> files. It was essentially a failure as a file format and will be deprecated >> in PDF 2.0. If the goal of archiving with PDF/A is to produce reliable >> files, JPEG 2000 conflicts with that goal. >> >> This is VERY interesting information, I have two questions, if you know: >> 1. Do you have a link to the PDF 2.0 spec where it says that JPEG2000 will >> be deprecated? > > Apparently I'm wrong about this, the PDF 2.0 spec is still going through > working groups so I only hear rumours. Some things are definitely getting > deprecated, such as FDF forms!
Of course what I meant to say was XFA, not FDF! > >> 2. What would be your suggestion for non-lossy compression for color images >> in PDF files? I know LZW is an answer, but the compression is much worst >> than JPEG2000. > > First of all I'd check if a maximum-quality JPEG isn't good enough. It > usually is. If you really need lossless (and as you're archiving you might > well do) then PNG is simple and reliable. There are ways to losslessly > optimise the colour palette to reduce file size a bit. Also make sure you use > the right colour space - a b&w raster is 1/3 the size of an RGB one. > >> Can you think of a solution that brings a compression close >> to that of JPEG2000 without losing information? > > No, though it does depend on what's in your images. Black and white line art > will compress well with pretty much any approach - photographs not so much. > If you have 1-bit images (literally black and white) then your job is > particularly easy. > >> And of course I am not >> considering re-encoding a JPEG image, this is pointless as you mentioned. > > Ok, good! > >> By the way: I read in the spec that JPEG2000 also works for b&w images, yet >> adobe acrobat cannot read b&w jpeg2000 images encoded with jai... don't know >> if this is because of jai or because of acrobat. Any idea? > > Off the top of my head I don't know but PDF does allow JPX images to embed > their own colour space. PDF only supports the "baseline" JPX features - so > you might want to check if that includes b&w. > > -- John > >> Costas >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: [email protected] >> For additional commands, e-mail: [email protected] >> --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
