Re:PSD is not my favourite file format (2009)
by nradov on Thursday January 28, 2021 @02:31PM
(#25947650)
That was very common not long ago. Even the JPEG/EXIF image file format is designed that way. So it's efficient for reading and writing, but introduces a lot of potential bugs with alignment and chunk size issues. Inserting an additional EXIF tag is a huge hassle because then you have to recalculate all the pointers, even those in other data chunks.
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Re:PSD is not my favourite file format (2009)
by just_for_you on Thursday January 28, 2021 @03:43PM
(#25948898)
One form of true insanity is probably JPEG-encoded TIFF files. Apparently it's so bad that for the next version of the TIFF specification they are taking that insane approach out completely.
I can't do justice to the article on TIFF's problems with JPEG (http://www.simplesystems.org/libtiff/TIFFTechNote2.html), but my understanding is that:
1) Some JPEG-specific data is moved outside of the actual JPEG bitstream tag, and into separate TIFF tags, making editing JPEG-in-TIFF files non-trivial. 2) Size is not encoded in some of these fields, so the TIFF editor you're writing will have to partially implement a JPEG decoder just to know the size of some of those TIFF tags, and 3) Some tags/fields are pointers into other parts of the TIFF file, meaning if you edit the file, you'll have to update the file in many places.
(As a quick aside on insane formats, may I also mention the EPWING dictionary format?)