Fred, can you repeat your test with a size, using a recent IM version, eg:

Code: Select all

```
magick -size 1x1 xc:"rgb(25,128,50)" -format "%[fx:standard_deviation]\n" info:
magick -size 2x1 xc:"rgb(25,128,50)" -format "%[fx:standard_deviation]\n" info:
magick -size 3x1 xc:"rgb(25,128,50)" -format "%[fx:standard_deviation]\n" info:
```

Perhaps these now give three different numbers. Or perhaps only two. Huh? Do they have the same mean?

Please also try different colours, eg black and white. Is the SD of a white pixel different to the SD of a black pixel? I can't see why it should be different.

As far as I can see, the SD of each result should be zero. Because the SD is the sqrt of the variance from the mean. And none of them have any variance from the mean, so the SD is zero.

The number of channels isn't relevant, because the calculation will use the "colour distance" between pixels, ie sqrt(dr^2+dg^2+db^2).