Legacy ImageMagick Discussions Archive

It is not a parenthesis is problem. It gives the same solution because subtraction come later than division.
I think I found the solution converting to text file:
convert image.png image.txt


convert d0-2017-10-13.jpg -separate -delete 1 -fx '((u[1]*255/231-u[0]/ u[1]*255/231+u[0])+1)/2' d0ndvi ...

Near the plants, I putted a white target that I cropped in white.jpg.
convert white.jpg -resize 1x1\! -format "%[pixel:u]\n" info: >white.txt
white.txt contain this text line:
srgb(255,170,231)

I tried to make a white balance adding *255/231 to the blue channel and follow fmw42 suggestion.
convert ...

Thank you for your reply.
Yes, adding 0.5 gives a brighter images but with different contrast.
The range of Ndvi index should be between -1 and 1; I was wondering how the different commands 'convert' it in the range of 0-255 values.
I'm going to compare a series of images of differently fertilized ...

I'm trying to calculate the ndvi index using imagemagick in spite of proprietary software, but I obtain different results using different methods with the same mathematical expression.

In a linux console:
convert d0-2017-10-13.jpg -separate d0-%d.png
convert d0-0.png d0-1.png d0-2.png -fx '(u[2 ...

I can' find how to convert my table in a format useful for netpbm

Hi, this is my first post.
Debian 8, imagemagick gui do not work.
I need to compute ndvi from a jpg photo.
https://it.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index
I converted jpg in txt by terminal commands:
convert filtrorosso.jpg filtrorosso.txt
sed -e 's/ //g' -e 's/(//g' -e 's ...