Question 355477 in PHP Question posted in
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Php – How to get image red green blue standard deviation values from gm identify -verbose?

I am trying to get the values given for Standard Deviation in the Red, Green, and Blue channels that you can see in gm identity -verbose but they’re not listed in the -format options.

How can I get these from the commandline?

A workaround to list the values using PHP:

    $raw = `gm identify -verbose {$file}|grep -E -e '^ +(Standard Deviation): *[^b]*$'`;
    preg_match_all("/(?<=Standard Deviation:)(?: +)([d.]+)/", $raw, $matches);
    $ret = [$matches[1][0], $matches[1][1], $matches[1][2]];

this is the output from gm identify -verbose.
Example we need the values from properties under Channel Statistics:

Image: /.../.../img.jpg
  Format: JPEG (Joint Photographic Experts Group JFIF format)
  Geometry: 1064x1600
  Class: DirectClass
  Type: true color
  Depth: 8 bits-per-pixel component
  Channel Depths:
    Red:      8 bits
    Green:    8 bits
    Blue:     8 bits
  Channel Statistics:
    Red:
      Minimum:                     0.00 (0.0000)
      Maximum:                   255.00 (1.0000)
      Mean:                      132.32 (0.5189)
      Standard Deviation:         45.92 (0.1801)
    Green:
      Minimum:                     0.00 (0.0000)
      Maximum:                   255.00 (1.0000)
      Mean:                      104.17 (0.4085)
      Standard Deviation:         55.13 (0.2162)
    Blue:
      Minimum:                     0.00 (0.0000)
      Maximum:                   255.00 (1.0000)
      Mean:                      103.61 (0.4063)
      Standard Deviation:         55.71 (0.2185)
  Filesize: 452.0Ki
  Interlace: No
  Orientation: Unknown
  Background Color: white
  Border Color: #DFDFDF
  Matte Color: #BDBDBD
  Page geometry: 1064x1600+0+0
  Compose: Over
  Dispose: Undefined
  Iterations: 0
  Compression: JPEG
  JPEG-Quality: 95
  JPEG-Colorspace: 2
  JPEG-Colorspace-Name: RGB
  JPEG-Sampling-factors: 2x2,1x1,1x1
  Signature: 136912e901ae9314fd683868418cae1f5d838c6891ddd8c13ce28057fb39365a
  Tainted: False
  User Time: 0.010u
  Elapsed Time: 0m:0.014459s
  Pixels Per Second: 112.3Mi
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2

Answers


  1. Chosen as BEST ANSWER
    0

    The solution that worked for me on macos was based on the answer from @thefourthbird. I couldn't install ggrep but had success with pcre2grep from port (macports).

    gm identify -verbose img.jpg|
pcre2grep -o --allow-lookaround-bsk "b(?:Minimum|Maximum|Mean|Standard Deviation): +d+.d+ (Kd+.d+"

    the --allow-lookaround-bsk option in pcre2grep enabled the K symbol which was needed to discard the content before each value.

    The result is the extracted values I can use from the example in the question:

    0.0000
1.0000
0.5189
0.1801
0.0000
1.0000
0.4085
0.2162
0.0000
1.0000
0.4063
0.2185

    Note: the number of values varies.

    • monochrome images only have 1 channel
    • color images (see example) have 3 for red, green, and blue.
    • each channel will always have 4 values: Minimum|Maximum|Mean|Standard Deviation

  2. 0

    Using GNU Grep, where -o prints only the matched parts and -P for Perl-compatible regular expressions:

    grep -oP "bStandard Deviation:h+Kd[d.]*"

    The pattern matches:

    • bStandard Deviation: Match literally starting with a word boundary
    • h+ Match 1+ horizontal whitespace characters
    • K Forget what is matched so far
    • d[d.]* Match a single digit followed by optional digits or dots (or [d.]+ but note that it could also only match dots

    You might also use [d.]+ but that could also match dots only. Using .?d[d.]* could match an optional leading dot, or a more strict format not allowing consecutive dots .?d+(?:.d+)*b

    See the regex matches.

    Or an alternative using sed

    sed -n 's/^[[:space:]]+Standard Deviation:[[:space:]]+([[:digit:]][[:digit:].]*).*/1/p'
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