https://bugzilla.wikimedia.org/show_bug.cgi?id=23258

--- Comment #3 from Tim Starling <[email protected]> 2010-06-22 09:36:54 
UTC ---
I've done some more testing and reading and I have to make a couple of
corrections:

Tiled images are designated by TileWidth and TileLength, not RowsPerStrip. See
the TIFF 6 spec, section 15. TileWidth and TileLength are both required to be
multiples of 16, so 16 is the lowest sensible value. 

However, untiled images appear to work with im_shrink without using additional
memory. So it's not necessary to check TileWidth anyway.

For my test file which is 6051x8901 (53.8 Mpx), scaling down by a factor of 10
in both directions, memory usage was as follows:

Method            | Tile size     | Memory usage (MB)
------------------------------------------------
im_shrink         | 128x128       | 35
im_shrink         | 64x64         | 37
im_shrink         | untiled       | 35
im_resize_linear  | 128x128       | 173
im_resize_linear  | 64x64         | 175
im_resize_linear  | untiled       | 173
ImageMagick       | 128x128       | 432

Memory usage was measured by counting mmap2() and munmap() calls with strace.

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