PSD Commenting

comments.m

while ([fh offsetInFile] + 12 <= imageoffs) {
  uint32_t sign = [fh readUInt32BE];
  uint32_t marker = [fh readUInt32BE];
  uint32_t chunklen = [fh readUInt32BE];
  off_t nextchunk = [fh offsetInFile] + ((chunklen + 3) & ~3);
 
  // At this point, I'd like to take a moment to speak to you about the Adobe PSD format.
  // PSD is not a good format. PSD is not even a bad format. Calling it such would be an
  // insult to other bad formats, such as PCX or JPEG. No, PSD is an abysmal format. Having
  // worked on this code for several weeks now, my hate for PSD has grown to a raging fire
  // that burns with the fierce passion of a million suns.
  //
  // If there are two different ways of doing something, PSD will do both, in different
  // places. It will then make up three more ways no sane human would think of, and do those
  // too. PSD makes inconsistency an art form. Why, for instance, did it suddenly decide
  // that these particular chunks should be aligned to four bytes, and that this alignment
  // should not be included in the size? Other chunks in other places are either unaligned,
  // or aligned with the alignment included in the size. Here, though, it is not included.
  // Either one of these three behaviours would be fine. A sane format would pick one. PSD,
  // of course, uses all three, and more. 
  //
  // Trying to get data out of a PSD file is like trying to find something in the attic of
  // your eccentric old uncle who died in a freak freshwater shark attack on his 58th
  // birthday. That last detail may not be important for the purposes of the simile, but
  // at this point I am spending a lot of time imagining amusing fates for the people
  // responsible for this Rube Goldberg of a file format. 
  //
  // Earlier, I tried to get a hold of the latest specs for the PSD file format. To do this,
  // I had to apply to them for permission to apply to them to have them consider sending me
  // this sacred tome. This would have involved faxing them a copy of some document or other, 
  // probably signed in blood. I can only imagine that they make this process so difficult
  // because they are intensely ashamed of having created this abomination. I was naturally
  // not gullible enough to go through with this procedure, but if I had done so, I would
  // have printed out every single page of the spec, and set them all on fire. Were it
  // within my power, I would gather every single copy of those specs, and launch them on a
  // spaceship directly into the sun. 
  //
  // PSD is not my favourite file format.

  if (sign != "8BIM") break; // sanity check

  switch (marker) {
    case "Lr16":
      layers = [XeePhotoshopLayerParser parseLayersFromHandle:fh parentImage:self alphaFlag:NULL];
    break;