Tag Archives: JPEG 2000 for Pascal

PasJpeg2000 Update in Progress

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I'm currently rewriting much of a Jpeg 2000 for Pascal library. There is a new IO class responsible for decoding and encoding of Jpeg 2000 files instead of only VCL TBitmap descendant. It's cross platform and with only Delphi/FPC RTL dependencies. VCL and LCL TGraphic classes will be built using this IO class but it can be used independently as well (Imaging library will use it too).

New features of Jpeg 2000 for Pascal will be CMYK colorspace support and also indexed/palettized images support (yes, it's possible to have image using palette in Jpeg 2000). These features as well as proper alpha channel definitions are patched into OpenJpeg library. Its team is not very active in incorporating larger patches into their code, so patches will probably always be additional step for people who want to recompile OpenJpeg themselves for use with PasJpeg2000.

You can follow the progress of the new version in SVN repository here: branch v120.

PasJpeg2000 News

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JPEG 2000 for Pascal project is based on OpenJpeg library. For a very long time there was a bug that caused alpha (fourth and subsequent image channels) channel to be saved with all the samples having the value of 0.5 (128 for 8bit channels). This buggy behavior also depended on compiler settings - optimization level in case of GCC. You could use at most O1 in Windows and Linux, and only O0 in Mac OS X. Bug was also present when compiling with C++ Builder (to get object files usable in Delphi) but only when irreversible DWT transformation was enabled in OpenJpeg during encoding (it wasn't before, but working versions of both PasJpeg2000 and Imaging use it now when lossy compression is selected by user to get smaller files).
You can read more about it in this news group post. Basically it was all fixed by changing a condition in one if statement to prevent accessing the fourth element of a three element array.

So what can you expect in the next version of PasJpeg2000 library?
Higher GCC optimization levels should make it a lot faster when using Free Pascal (particularly in Mac OS X where O0 was used). Irreversible DWT transformation produces smaller lossy files than current PasJpeg2000 version and with optional MCT (multicomponent transform - basically RGB>YCbCr) you get even smaller ones. There's now also a patch that enables OpenJpeg to get palettes from JP2 files so indexed JPEG 2000 images could be supported too. And finally, there are some bug fixes (wrong reconstruction of subsampled files, ...).

First JPEG 2000 for Pascal Release

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I finally released first version of JPEG 2000 for Pascal library. It’s based on translated header and precompiled OpenJpeg library that was part of Imaging for a long time – now released separately.

There’s header translation working with both Delphi and FPC and original C library precompiled to object files (Delphi) and static libraries (FPC for Win32, Linux x86/x64, and Mac OS X).

I’ve written simple TBitmap descendant that loads and saves JPEG 2000 images. It’s only for Delphi now – can’t do LCL version with just few IFDEFS, there are lot more changes between VCL and LCL TBitmaps. I plan to write separate LCL version for one of upcoming releases (using TFPCustomImageWriter and TFPCustomImageReader classes).

You can get JPEG 2000 for Pascal library at it’s project page.