Heap size larger than expected

[TedBaker]

I have the following 2.3905GB grayscale file.

Code: Select all

$ identify n10_757_a_full4800_exp1_001.tif 
n10_757_a_full4800_exp1_001.tif TIFF 27360x43680 27360x43680+0+0 16-bit Grayscale Gray 2.3905GB 0.010u 0:00.000

a simple rotate 90 results seems to require 8.9G?

Code: Select all

convert -define registry:temporary-path=. -debug cache n10_757_a_full4800_exp1_001.tif -rotate 90 test.tif
2017-11-24T22:19:43+00:00 0:00.000 0.000u 6.9.7 Cache convert-im6.q16[16740]: cache.c/DestroyPixelCache/1123/Cache
  destroy 
2017-11-24T22:19:43+00:00 0:00.000 0.000u 6.9.7 Cache convert-im6.q16[16740]: cache.c/DestroyPixelCache/1123/Cache
  destroy 
2017-11-24T22:19:43+00:00 0:00.000 0.000u 6.9.7 Cache convert-im6.q16[16740]: cache.c/OpenPixelCache/3873/Cache
  open n10_757_a_full4800_exp1_001.tif[0] (Heap Memory, 27360x43680 8.9041GiB)
2017-11-24T22:19:48+00:00 0:04.550 4.440u 6.9.7 Cache convert-im6.q16[16740]: cache.c/SetPixelCacheExtent/3737/Cache
  extend n10_757_a_full4800_exp1_001.tif[0] (./magick-167400e1kgOGdG18u[3], disk, 9.5607GB)
2017-11-24T22:19:48+00:00 0:04.550 4.440u 6.9.7 Cache convert-im6.q16[16740]: cache.c/OpenPixelCache/4022/Cache
  open n10_757_a_full4800_exp1_001.tif[0] (./magick-167400e1kgOGdG18u[-1], Map, 43680x27360 8.9041GiB)
2017-11-24T22:20:40+00:00 0:56.410 25.240u 6.9.7 Cache convert-im6.q16[16740]: cache.c/DestroyPixelCache/1123/Cache
  destroy n10_757_a_full4800_exp1_001.tif[0]
2017-11-24T22:21:13+00:00 1:30.070 41.670u 6.9.7 Cache convert-im6.q16[16740]: cache.c/DestroyPixelCache/1123/Cache
  destroy n10_757_a_full4800_exp1_001.tif[0]

Is this because IM allocates room for three channels? A color file with the same number of pixels using the same heap size.

If so Is there any parameters to reduce the heap size if only one channel is in use?

[dlemstra]

ImageMagick 6 will allocate room for 5 channels. You might get a lower memory footprint when you switch to ImageMagick 7.

p.s. The size on disk will not be the same amount of memory when decoded because the pixels are compressed.

[TedBaker]

Thanks, in which case it seems to make sense to increase the memory limit beyond the physical ram, I have 12G, and

identify -list resource shows Memory: 11.445GiB, changed them convert command too:

convert -limit 20G infile outfile

and no need to for any temporary files.

[fmw42]

As dlemstra mentioned, IM 6 will need memory for 5 channels even for a gray level image. But in IM 7 a gray level image only needs memory for one channel. So you might consider upgrading to IM 7.

[TedBaker]

Thanks fred, I will upgrade at some point. My follow up was just offered as 'way around' the 'issue' by just allocating more memory, than ideal, for grayscale images only.

I assume the default limit for memory is set at the physical limit, by increasing it to some sensible amount above the amount of RAM, you can avoid the use of disk, as I assume the pages for the 4 unused channels are never or hardly actually used.

[fmw42]

For a grayscale to grayscale processing in IM 6, you will need to allocate at least RAM for 10 times the image size (5 channels for the input and 5 channels for the output), plus any clones or mpr: copies for intermediate processing. In IM 7 you would only need 2 times the image size (1 for input and 1 for output), etc.