Problems opening a certain CR2 files

Question

Hi,Can anyone help with this one, in May last year I shot some images on a Canon 450D in RAW, when I imported them into Aperture, they showed the unsupported message, Apple then updated aperture and now they only open as a thumb nail, I thought I might have mistakenly shot these in sRAW so tried opening in the Canon software but still no joy. In the metadata it shows a pixel size of 170 x 256 but a file size of 15.55mb which really doesn't make sense.
Please help if you can.
Regards
Steve

Answer 1

There are 2 issues here that combine to cause them not to open: the way the files were written, and how much memory Photoshop will allocate for decompressing a single image tile.
Image Width: 14101 Image Length: 18206
  Resolution: 400, 400
  Bits/Sample: 8
  Compression Scheme: PackBits encoding
  Samples/Pixel: 3
  Rows/Strip: 18206
  Number of Strips: 1
The images are written as one huge image tile/strip that decompresses to something around a Gig per tile.
Decompressing that quickly is going to require allocating a buffer over a Gigabyte to hold the data.  Photoshop sets some limits on how large a tile buffer it will allocate so that you don't wait hours for the OS and Photoshop to free up the required space. Yes, we really had user documents that were spinning for an hour or more trying to allocate the buffer space to decompress them, even on a 64 bit system with quite a bit of RAM - hence the limits.  Your documents, written as a single huge tile, exceed the limits that Photoshop will allocate for a single tile.
The TIFF spec recommends that documents be saved in smaller tiles (though one line per tile is excessive).  Even moving to a few hundred Meg per tile would allow Photoshop to decompress the image data successfully.  Either you should choose different TIFF output options when scanning, or communicate to the makers of the scanner that they should read the TIFF specification and talk to Adobe about improving their TIFF implementation (which would send them back to me).
Also, the images are also written using PackBits (a run length encoding scheme) that is not a great compressor.  Using LZW or Flate would have decreased the size of the files considerably (half the size, or better).
For the time being, you can use some of the libTiff command line tools to unpack and repack these files to work better with Photoshop and other applications.