Dynamic blur command

[Videomajk]

Hello

I'm trying to create a dynamic blur effect where the sigma value is dependent on other image value. I've tried this:

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-blur 0x%%[fx:h/400]

I understand from other posts that this is not supported by the blurr command. Is there Another way of achiving this effect?
My IM version is 6.9.7 on Win10.

[snibgo]

The magick you need is "-compose blur".

See http://www.imagemagick.org/Usage/mapping/#blur and examples on my "Selective blur" page.

[snibgo]

Correction to the above: I think I misunderstood what you want.

I now think you want a constant blur for a given image, a constant sigma, but that will depend on an expression, eg:

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magick toes.png -blur 0x%[fx:h/400] b.png

This works in v7, but is not available in v6.

For v6, you can first calculate the sigma as an environment variable:

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for /F "usebackq" %L in (`identify -format "SIG=%[fx:h/400]" toes.png`) do set %L

convert toes.png -blur 0x%SIG% b.png

If using BAT files, don't forget to double the % signs as required.