A way to perform the +level ImageMagick operation in Wand?

Question

Using the +level ImageMagick operator (https://imagemagick.org/script/command-line-options.php#level) in command line will produce an output image with the channel values of the

Answer 1

Sorry, I do not know Wand syntax that well. Perhaps someone who does can add to this answer or post another that provides the proper syntax.

But you can achieve the equivalent to +level using the wand function command with argument polynomial, where the polynomial arguments are the equivalent of the equation a*x+b. See http://docs.wand-py.org/en/0.5.1/wand/image.html.

You have to compute a and b from your values and the following equation to achieve the equivalent of +level.

a*X+b = Y

When X=0, then Y=0.45.

When X=1, then y=0.70.

So we have two linear equations that need to be solved.

0*a+b=0.45

1*a+b=0.70

From the top equation, you have

b=0.45

Substitute b into the bottom equation and get

a+0.45=0.70 --> a=0.25

In ImageMagick, you would then use

convert image.suffix -function polynomial "0.45, 0.25" result.suffix

See https://imagemagick.org/Usage/transform/#function_polynomial

In Wand function, you will need to select polynomial and then provide the a and b values above.

A guess at the Wand function syntax would be something like:

from wand.image import Image
with Image(filename='yourimage.suffix') as img:
   a = 0.25
   b = 0.45
   img.function('polynomial', [a, b])
...