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I several TIFF images in a folder. How can I determine which image compression algorithm they use?

When I do file I get

100 (2).tif:                 TIFF image data, little-endian
100.tif:                     TIFF image data, little-endian

These results don't say which algorithm is used, or even whether it's lossy or lossless. How can I figure this out? Solutions can be Windows- or Linux-based.

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1  
Looking at the image's extension should be enough. –  Icarus Mar 20 '12 at 13:52
    
isn't the extension a sufficient information? else, file gives you the basic infos on a file (linux/macosx) –  njzk2 Mar 20 '12 at 13:52
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Most compression algorithms include a header with a fixed tag of some form. It wouldn't be too much of a challenge to roll your own identifier. –  adelphus Mar 20 '12 at 13:53

3 Answers 3

up vote 4 down vote accepted

Use W_Whalley's identify -verbose suggestion instead. If you're in a linux/cygwin environment, pipe it to grep -i compression and you'll have your one-line answer. I.e.

identify -verbose /path/to/your/file.tiff | grep -i compression

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What about the file command? Example:

$ file /usr/share/apache2/icons/a.png
/usr/share/apache2/icons/a.png: PNG image, 20 x 22, 4-bit colormap, non-interlaced
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But where is the name of the algorithm used ? –  klijo Mar 20 '12 at 14:49
    
PNG is a compression algorithm (a lossless one). Image file formats are typically named after thier compression algorithm. The term "JPEG" for example, doesn't technically refer to a file type; it refers to a compression scheme. Colloquially the two are pretty universally conflated, but the type of image (TIFF, PNG, etc.) usually (but not always) refers to the compression algorithm used. –  Zac B Mar 20 '12 at 15:04
    
TIFF can be made to work with both lossless and lossy compression. This is my real problem. I need to determine which of them uses lossy and which uses lossless and the name of the algorithm –  klijo Mar 20 '12 at 15:14
    
Sorry, TIFF was a bad example. The TIFF format usually uses LZW, but there are (rare, but present) implementations of it that use other algorithms as well. –  Zac B Mar 20 '12 at 15:16
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Use W_Whalley's identify -verbose suggestion instead. If you're in a linux/cygwin environment, pipe it to grep compression and you'll have your one-line answer. –  Zac B Mar 20 '12 at 17:21

If you have imagemagick installed, use the display tool to show the image. Right-click on the image and choose Image Info, then look for the Compression: setting (it's near the bottom of the list). Or if you want the minimum information use the identify tool with the -verbose switch, then filter the result to look for the Compression line.

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