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On Mac OS X how can I change screenshots to save as low res JPG insetad of a PNG? I also have quicksilver installed and use the "capture region" shortcut quite often - not sure if that would have any effect on the answer here.


The answer below is great for getting a jpg version. Thanks!

But is there some way to get a low res version though? Or possibly a script I could use to convert to a low res version? Maybe with quicksilver? Or a screen cap utility that would allow me to set the jpg quality?

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up vote 2 down vote accepted

defaults write type jpg to change the default format.

#!/usr/bin/env bash

cd /2/screenshots/
x=$(date +"%y%m%d%H%M%S")
screencapture -i -o $x.png
sips -s format jpeg -s formatOptions 60 $x.png -o $x.jpg
rm $x.png

screencapture flags:

  • -i = interactive / selection
  • -o = no shadows in window mode
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Thanks for this awesome answer! If I wanted to convert it to black and white, how would I do that? – cwd Jun 12 '11 at 8:12
Install ImageMagick (for example sudo port install imagemagick), and convert <image> -colorspace Gray <image> or convert <image> -fx '(r+g+b)/3' <image>. – user495470 Jun 12 '11 at 17:17

Lifted from here: in 10.4 and up you can change the format used for the screen shot image by editing some hidden options. Open up Terminal and type:

defaults write type image_format
killall SystemUIServer

Where image_format can be one of the following: jpg, tiff, pdf, png, bmp or pict. The article mentions "among others" so other format options might be possible too.

So in your case:

defaults write type jpg
killall SystemUIServer

would get you JPEG screen shots instead of PNG.

The resolution or quality of the image does not appear to be configurable. I'm pretty sure you get a 1:1 pixel capture. For example, I just took a Cmd-Shift-3 capture of my iMac desktop and file info is telling me the image is 1900 x 1200 pixels -- exactly the same size as my screen resolution.

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Thanks! Anybody else have some ideas on a way to get a low res version? – cwd Jun 12 '11 at 3:25
I gave you an upvote for the default image type, but the low res is more important to me so I've accepted Lri's answer. Thanks :) – cwd Jun 12 '11 at 4:45

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