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Is there a command I can use to convert a .jpg or .png or other to extension to a .ico? If possible also to resize it to be a favicon size?

I'd also like to turn it from .ico to .jpg or .png.

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3 Answers 3

Reset to default
83

The most useful program (suite) to manipulate image is Imagemagick (sudo apt install imagemagick) and for this task you will need the convert binary.

You will need to use something like:

convert -resize x16 -gravity center -crop 16x16+0+0 input.png -flatten -colors 256 -background transparent output/favicon.ico
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2
  • It doesn't keep the transparent section of the image. The alpha channel changed to white. I don't know why.
    – xdnroot
    Oct 21, 2020 at 12:41
  • 3
    The removal of transparency is most likely due to using the -flatten flag.
    – Andy
    Oct 28, 2020 at 7:40
30

This is the best command to do that from console:

convert <your-image-here> -define icon:auto-resize=256,64,48,32,16 favicon.ico

Hope you like it!

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4
  • 1
    What does the -define icon:auto-resize=256,64,48,32,16 do? The man pages just says that it -define "defines one or more image format options"
    – Peter T.
    Nov 1, 2021 at 14:49
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    icon:auto-resize to automatically store multiple sizes in an ico image (requires 256x256 input image).
    – rodvlopes
    Jun 19, 2022 at 14:13
  • In my case, this command handled also the transparency of the source PNG better than the command in the answer off @systho.
    – wittich
    Jul 12, 2023 at 7:11
  • This should be the accepted answer IMO. The accepted answer results in a blurry image for me.
    – Astral Axiom
    Aug 9, 2023 at 11:23
4

Use this zsh function:

png2ico () {
    local i="${1}" o="${2:-${1:r}.ico}" s="${png2ico_size:-256}"
    convert -resize x${s} -gravity center -crop ${s}x${s}+0+0 "$i" -flatten -colors 256 -background transparent "$o"
}

Like so:

png2ico input.png
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1
  • works also with other file format that are supported by Imagemagick, not just png
    – Peter T.
    Nov 1, 2021 at 14:48

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