til/mac/check-properties-of-an-image-with-sips.md

Check Properties Of An Image With sips

I used Figma to create a basic design for a t-shirt screenprinting. Before I sent the image asset off to the printer, I needed to verify a couple properties of the image where right.

My first thought was that there is probably a way to do this with ffmpeg, but I intentionally asked Claude in a non-leading way how to do this. It surfaced a Mac-specific utility I'd never heard of -- sips (Scriptable Image Processing System).

Sometimes it is hard to tell if an image exported correctly with transparent background (alpha channel). Part of how I was able to verify that was to point sips at the PNG file and ask if it has an alpha channel. The -g flag (short for get property) is the way to output a property like this.

❯ sips -g hasAlpha ~/Downloads/Untitled/orange-shirt-print-front.png
/Users/lastword/Downloads/Untitled/orange-shirt-print-front.png
  hasAlpha: yes

I then wanted to check that the dimensions of the image were right. I had carefully sized the canvas in Figma to correspond to specs required by the printer. Similar to above, I can use -g to grab the pixelWidth and pixelHeight properties of the image.

Unfortunately the pixel dimensions of the exported PNG were not what I was expecting.

❯ sips -g pixelWidth -g pixelHeight ~/Downloads/Untitled/orange-shirt-print-front.png
/Users/lastword/Downloads/Untitled/orange-shirt-print-front.png
  pixelWidth: 1152
  pixelHeight: 1536

I then found some additional export settings in Figma and tried again. Nailed it.

❯ sips -g pixelWidth -g pixelHeight ~/Downloads/Marty\ Supreme\ —\ 12\ ×\ 16\ in\ print.png
/Users/lastword/Downloads/Marty Supreme — 12 × 16 in print.png
  pixelWidth: 3600
  pixelHeight: 4800

See man sips for more details.