If I want to optimize an image by solely shrinking the dimensions, ImageMagick has a command to do this.

convert image.png -resize 50% image.png # This will shrink the image by 50% and overwrite itself

Although, I wanted to generate a shorter version of this where I always know I want to replace the image inplace and I don't have to remember the syntax for the -resize flag, as it is non-standard (Where single letter flags have a single dash and words have two dashes). I wrote a simple zsh function that I put in my ~/.zshrc file to do this:

img-resize(){
	convert $1 -resize $2 $1
}

Now that previous command can be shorted to

img-resize image.png 50%