Use o comando identify , que faz parte do ImageMagick.
Exemplos:
$ identify ZEAKR.jpg
ZEAKR.jpg JPEG 400x600 400x600+0+0 8-bit DirectClass 49.9KB 0.000u 0:00.000
ou
$ identify -verbose ZEAKR.jpg
Image: ZEAKR.jpg
Format: JPEG (Joint Photographic Experts Group JFIF format)
Class: DirectClass
Geometry: 400x600+0+0
Resolution: 72x72
Print size: 5.55556x8.33333
Units: Undefined
Type: TrueColor
Endianess: Undefined
Colorspace: RGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
Channel statistics:
Red:
min: 0 (0)
max: 255 (1)
mean: 37.8679 (0.148501)
standard deviation: 83.5317 (0.327575)
kurtosis: 1.46576
skewness: 1.83875
Green:
min: 0 (0)
max: 255 (1)
mean: 60.6554 (0.237864)
standard deviation: 54.9167 (0.21536)
kurtosis: 1.74308
skewness: 1.84745
Blue:
min: 0 (0)
max: 255 (1)
mean: 67.6817 (0.265418)
standard deviation: 28.1072 (0.110224)
kurtosis: 0.599932
skewness: -0.97633
Image statistics:
Overall:
min: 0 (0)
max: 255 (1)
mean: 55.4017 (0.217261)
standard deviation: 59.9539 (0.235113)
kurtosis: 2.34592
skewness: 1.64301
Rendering intent: Undefined
Interlace: None
Background color: white
Border color: rgb(223,223,223)
Matte color: grey74
Transparent color: black
Compose: Over
Page geometry: 400x600+0+0
Dispose: Undefined
Iterations: 0
Compression: JPEG
Quality: 96
Orientation: Undefined
Properties:
date:create: 2012-06-23T11:22:15-05:00
date:modify: 2012-06-23T11:22:15-05:00
jpeg:colorspace: 2
jpeg:sampling-factor: 1x1,1x1,1x1
signature: 2beab0779fc657fb62e8609b600d90d1e502f614794e497299ffaa28d145408e
Artifacts:
verbose: true
Tainted: False
Filesize: 49.9KBB
Number pixels: 240KB
Pixels per second: 24MB
User time: 0.000u
Elapsed time: 0:01.009
Version: ImageMagick 6.6.9-7 2012-04-30 Q16 http://www.imagemagick.org