ImageMagick
Documentation issue for -evaluate is missing some options
ImageMagick version
7.1.1.44
Operating system
MacOS
Operating system, version and so on
Ventura
Description
On the page at https://imagemagick.org/script/command-line-options.php#evaluate
the list of options is missing some compared to my running
magick -list evaluate
which gives me
Abs
Add
AddModulus
And
Cos
Cosine
Divide
Exp
Exponential
GaussianNoise
ImpulseNoise
InverseLog
LaplacianNoise
LeftShift
Log
Max
Mean
Median
Min
MultiplicativeNoise
Multiply
Or
PoissonNoise
Pow
RightShift
RMS
RootMeanSquare
Set
Sin
Sine
Subtract
Sum
Threshold
ThresholdBlack
ThresholdWhite
UniformNoise
Xor
This pertained to my use of -evaluate-sequence sum
Steps to Reproduce
see above
Images
None
We updated the operator list. Feel free to write up a description of any operator that is currently missing a description.
Is there a difference between -evaluate-sequence sum and -evaluate-sequence add?
Is there a difference between -evaluate add X and -evaluate sum X?
There are difference in the way -evaluate processed a single image and the way -evaluate-sequence processes multiple images. Should you not list all the relevant options in the section for -evaluate-sequence with relevant text for that?
Are all -evalute options relevant to -evaluate-sequence?
Is there a difference between -evaluate-sequence sum and -evaluate-sequence add?
As far as I can see (from experiment and reading the code) there is no difference.
Is there a difference between -evaluate add X and -evaluate sum X?
As far as I can see (from experiment and reading the code) there is no difference.
Are all -evalute options relevant to -evaluate-sequence?
Yes.
There are difference in the way -evaluate processed a single image and the way -evaluate-sequence processes multiple images.
Can you give an example of a difference?
Can you give an example of a difference?
add in -evaluate adds a value to an image
add in -evaluate-sequence adds two images
Yes. That is the general pattern.
-evaluate {operation} value applies the operation and value to all the images in the current list. For example, -evaluate add 23% will add 23% of QuantumLevel to all channels of all pixels of all immages.
-evaluate-sequence {operation} applies the operation to the first two images, then to the result and the third image, then to the result and the fourth image, and so on. For example, -evaluate-sequence add will add the second image to the first, then add the third image, and so on. This is the same as simply adding all the images.
Where did you find that documentation? I do not see it on the options page. -evaluate shows a list of options and explanation. But -evaluate-sequence does not. The options page needs a list of options with explanations relevant to it, since you see above that the meanings are different between -evaluate and -evaluate sequence. I am not sure what all the -evaluate options explanations are. Some are even missing.
The above is from my knowledge, but see also https://usage.imagemagick.org/layers/#evaluate-sequence
I agree, the documentation at https://imagemagick.org/script/command-line-options.php#evaluate could be improved.
Thanks. I did not know that was there. Nice to have that documentation. It is a start, but many more options exist and are not even explained there. I guess I will have to write some things up and change the options page, if I can figure out what the code does for the other options.