Trim image and output trim amount

[Oli414]

I'm trying to trim an image and output the trim amount,

So far I'm testing with:

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magick in.png -trim out.png

But I'm already getting stuck when trying to both output some info, and output an image in the same command:

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magick in.png -trim -format "Hello World" info:- out.png

Which won't work. Imagemagick's process won't exit.

How can I get both some text as output and an image saved in the same command? What variables would I then need to get the amount which was trimmed?

Version: 7.0.8-3 Q16
Right now I'm testing on Windows in a CMD window, but in the end, I'll be using subprocess.check_output in Python to get the info I need.

[snibgo]

To write info at any stage in a command, use "-write info". And you can "-write out.png" at any stage. The final output mustn't have "-write". So if you want to write info and an image:

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magick in.png -trim -write info: out.png

... or...

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magick in.png -trim -write out.png info:

If you want the trim data in a variable, you must use a shell facility. You don't say what shell you are using: bash, Windows CMD, Windows BAT, or whatever.

In your command with "info:-", IM interprets this as needing "info:" type data as input from stdin, so it is waiting to receive it. That's why it didn't complete.

[Oli414]

Thanks, that's all I needed!

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magick in.png -trim -format "%[fx:page.width/2 - page.x] %[fx:page.height/2 - page.y]" -write info: out.png

Allows to get me the untrimmed image's center within the newly trimmed image.

[GeeMack]

Allows to get me the untrimmed image's center within the newly trimmed image.

You can also get the trim information without actually doing the trim with a command like this...

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magick input.png -set page %[@] output.png

If the output format supports it, like PNG and TIF, the paging information of those FX variables "page.height", "page.width", "page.x", and "page.y" will be as if you trimmed it and be available in the output image while the image retains its original input dimensions. This can be helpful if you want to calculate for a particular "-shave" or "-chop" without trimming the entire image.