P.S.
I am not sure you need to do these by channel for min and max as I
think you get that naturally from the simpler formula,
__________________________________________
Prior to IM 6.3.9:
data=`convert image -verbose info:`
min=`echo "$data" | sed -n '/^.*[Mm]in:.*[(]\([0-9.]*\).*$/{ s//\1/; p; q; }'`
max=`echo "$data" | sed -n '/^.*[Mm]ax:.*[(]\([0-9.]*\).*$/{ s//\1/; p; q; }'`
mean=`echo "$data" | sed -n '/^.*[Mm]ean:.*[(]\([0-9.]*\).*$/{
s//\1/; p; q; }'`
std=`echo "$data" | sed -n '/^.*[Ss]tandard.*[(]\([0-9.]*\).*$/{
s//\1/; p; q; }'`
reports values in range 0 to 1
String Formats: Min, Max, Mean, Standard Deviation Introduced in IM 6.3.9-1
convert image -format "%[min]" info:
convert image -format "%[max]" info:
convert image -format "%[mean]" info:
convert image -format "%[standard-deviation]" info:
reports values in range 0 to QuantumRange
Above deprecated (but still supported) in IM 6.4.0-11 but now
convert image -format "%[fx:image.minima]" info:
convert image -format "%[fx:image.maxima]" info:
convert image -format "%[fx:image.mean]" info:
convert image -format "%[fx:standard_deviation]" info:
reports values in range 0 to 1. But you can now do math calculations
within these.
To get them by channel, you need to do the following:
minred=`convert image -channel Red -separate "%[fx:100*image.minima]" info:`
reports percent values (i.e. 0 to 100)
or
minred=`convert image -channel Red -separate
"%[fx:QuantumRange*image.minima]" info:`
reports values in range 0 to QuantumRange (8-bit: 0 to 255; 16-bit 0 to 65535)
Then you can substitute the variables into:
min=`convert xc: -format "%[fx:min($minred,$mingreen,$minblue)]" info:`
max=...
Then you can substitute these variables into:
convert image.jpg
-level $min,$max image2.jpg
Note: if using percent values then you need to add the percent sign %
convert image.jpg
-level $min%,$max% image2.jpg
Hello,
For proper color transformation with -level you have to check min,max
color values for each image separately. Is there a way to do it more or
less automatically with IM or other cross platform tool (Windows and
Linux)?
identify -verbose gives histogram values but 1) it takes ages to get
that info for big files 2) isn't easy to parse.
Correct info for level is something like:
convert image.jpg
-level (min(min r, min g, min b)),(max(max r, max g, max b)) image2.jpg
TIA
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