Question

Is there a cli way of getting the average value of all the pixels in an image

for example – if i have an all black image, I would want to type:

   *cmd* black-img.jpg 

and the output will be 0 in the shell

Answer 1

Oh, this is simple:

convert  image.jpg  -scale 1x1\!  txt:-

The command uses ImageMagick’s convert to enforce scaling of the input image to a size 1×1 pixels. Output will be something like this for an 8-bit RGBA image:

# ImageMagick pixel enumeration: 1,1,255,srgba
0,0: (151,161,212, 92)  #97A1D45C  srgba(151,161,212,0.361928)

or this for an 8-bit sRGB image:

# ImageMagick pixel enumeration: 1,1,255,srgb
0,0: (229,226,229)  #E5E2E5  srgb(229,226,229)

It represents the color value of the single-pixel image that was produced:

• 0,0: are the coordinates of this pixel: 1st row in 1st column.
• (151,161,212, 92) represent the R ed, G reen, B lue and A lpha values of the RGBA pixel.
• (229,226,229) represent the R ed, G reen and B lue values of the sRGB pixel.
• #97A1D45C and #E5E2E5 are the respective hex values.

Now it’s your own job to compute this output into ‘a '0' in the shell’ if it is a black pixel. 🙂