I'm also getting some strange numbers from the Perl Magick Statistics() method.
To illustrate (in Perl Magick - since I don't use the command line)
The (rather clumsy) code below generates a 3 pixel image including alpha channel and assigns different values to each pixel.
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my $image = Image::Magick->new;
my @pixel;
$image->Set(size=>'3x1');
$image->Read('canvas:black');
$image->Color(color=>'blue');
$image->Set(alpha=>'On');
$image->SetPixel(x=>0, y=>0, color=>[1,1,0.75,1]);
$image->SetPixel(x=>1, y=>0, color=>[1,0,0.5,0.2]);
$image->SetPixel(x=>2, y=>0, color=>[0,0,0.25,1]);
$image->Identify();
print "Mean r = ".$image->Get('%[fx:mean.r]')."\n";
print "Mean g = ".$image->Get('%[fx:mean.g]')."\n";
print "Mean b = ".$image->Get('%[fx:mean.b]')."\n";
print "Mean = ".$image->Get('%[fx:mean]')."\n";
print "Mean a = ".$image->Get('%[fx:mean.a]')."\n";
print "Mean o = ".$image->Get('%[fx:mean.o]')."\n\n";
print "Maxima r = ".$image->Get('%[fx:maxima.r]')."\n";
print "Maxima g = ".$image->Get('%[fx:maxima.g]')."\n";
print "Maxima b = ".$image->Get('%[fx:maxima.b]')."\n";
print "Maxima = ".$image->Get('%[fx:maxima]')."\n";
print "Max = ".$image->Get('%[fx:max]')."\n";
print "Maxima a = ".$image->Get('%[fx:maxima.a]')."\n";
print "Maxima o = ".$image->Get('%[fx:maxima.o]')."\n\n";
print "Minima r = ".$image->Get('%[fx:minima.r]')."\n";
print "Minima g = ".$image->Get('%[fx:minima.g]')."\n";
print "Minima b = ".$image->Get('%[fx:minima.b]')."\n";
print "Minima = ".$image->Get('%[fx:minima]')."\n";
print "Min = ".$image->Get('%[fx:min]')."\n";
print "Minima a = ".$image->Get('%[fx:minima.a]')."\n";
print "Minima o = ".$image->Get('%[fx:minima.o]')."\n\n";
my @stats = $image->Statistics();
my ($i, $j);
for ($i=0; $i<4; $i++) {
for ($j=0; $j<8; $j++) {
print $stats[$i*8+$j]."/";
}
print "\n";
}
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Image: black
Base filename: black
Format: CANVAS (Constant image uniform color)
Class: DirectClass
Geometry: 3x1+0+0
Units: Undefined
Type: PaletteAlpha
Base type: TrueColorAlpha
Endianess: LSB
Colorspace: sRGB
Depth: 8/16-bit
Channel depth:
Red: 1-bit
Green: 1-bit
Blue: 16-bit
Alpha: 4-bit
Channel statistics:
Pixels: 3
Red:
min: 0 (0)
max: 255 (1)
mean: 170 (0.666667)
standard deviation: 120.208 (0.471405)
kurtosis: -1.5
skewness: -0.707107
entropy: 0.918296
Green:
min: 0 (0)
max: 255 (1)
mean: 85 (0.333333)
standard deviation: 120.208 (0.471405)
kurtosis: -1.5
skewness: 0.707107
entropy: 0.918296
Blue:
min: 63.75 (0.25)
max: 191.25 (0.75)
mean: 127.5 (0.5)
standard deviation: 52.0517 (0.204124)
kurtosis: -1.5
skewness: 0
entropy: 1
Alpha:
min: 51 (0.2)
max: 255 (1)
mean: 187 (0.733333)
standard deviation: 96.1665 (0.377124)
kurtosis: -1.5
skewness: -0.707107
entropy: -nan
Image statistics:
Overall:
min: 0 (0)
max: 255 (1)
mean: 142.375 (0.558333)
standard deviation: 101.066 (0.396337)
kurtosis: -1.28206
skewness: -0.213977
entropy: 0.709148
Colors: 3
Histogram:
1: ( 0, 0, 64,255) #000040FF srgba(0,0,64,1)
1: (255, 0,128, 51) #FF008033 srgba(255,0,128,0.2)
1: (255,255,191,255) #FFFFBFFF srgba(255,255,191,1)
Rendering intent: Perceptual
Gamma: 0.454545
Chromaticity:
red primary: (0.64,0.33)
green primary: (0.3,0.6)
blue primary: (0.15,0.06)
white point: (0.3127,0.329)
Tile geometry: 3x1+0+0
Alpha color: grey74
Background color: white
Border color: srgb(223,223,223)
Transparent color: none
Interlace: None
Intensity: Undefined
Compose: Over
Page geometry: 3x1+0+0
Dispose: Undefined
Iterations: 0
Compression: Undefined
Orientation: Undefined
Properties:
date:create: 2017-02-09T11:00:47+00:00
date:modify: 2017-02-09T11:00:47+00:00
signature: 2721d18926bbdf0ebf14e8943047e4232109e609a135f0b82fdd882059921cc9
Tainted: True
Filesize: 0B
Number pixels: 3
Pixels per second: 3PB
User time: 0.000u
Elapsed time: 0:01.000
Version: ImageMagick 7.0.2-4 Q16 x86_64 2016-12-05 http://www.imagemagick.org
This appears to give all the correct statistical data.
The output from the various fx:maxima, minima and mean functions are as follows:
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Mean r = 0.666667
Mean g = 0.333333
Mean b = 0.5
Mean = 0.5
Mean a = 0
Mean o = 0
Maxima r = 1
Maxima g = 1
Maxima b = 0.749999
Maxima = 0.749999
Max = 0
Maxima a = 1
Maxima o = 1
Minima r = 0
Minima g = 0
Minima b = 0.250001
Minima = 0.250001
Min = 0
Minima a = 0.2
Minima o = 0.2
- fx:mean gives and incorrect value. It appears to actually give the value from fx:maxima.b
fx:mean.a and fx:mean.o give incorrect values. Interestingly if the fx:mean call (just before the fx:mean.a call) is omitted the value of fx:mean.a changes (but is still incorrect) !
fx:Maxima gives an incorrect value, again apearing to give the fx:maxima.b value.
fx:Minima - as above.
fx:Max & fx:Min give no values (and I didn't expect then to)
All others appear to function as expected.
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1/0/1/0.333333333333333/0.471404520791032/-1.5/0.707106781186548/0.91829583405449/
16/0.25/0.75/0.5/0.204124145231932/-1.50000000000001/0/1/
4/0.2/1/0.733333333333333/0.377123616632825/-1.50000000000001/-0.707106781186548/-nan/
1/2.74310389084049e+303/-2.74310389084049e+303/0/0/0/0/-nan/
Any chance you could take a look at these issues?
Regards
Mike
