Since iPhone4 with retina display was released everyone faces to unretina process. So every design is prepared in double size and then need to be scaled to be shown on non-retina displays.
I tried a few ways of scaling @2x images to @1x, so I want to share them.
1. Unretiner
First one and the simplest one is to use 3d part software. I tried Unretiner from the Mac AppStore. It does the job fast and easy as one click, but unfortunately not perfectly. And colors are distored. BTW, it’s definitely defined in the app description – “Great for testing out non retina devices before the big painful export from Photoshop.”
This is almost true. Keep going.
2. Automator
Next obvious thought for Mac users is to try to automate the process by your-self. Open Automator and quickly create own Workflow (or download already made one):
- “Find Finder Items” and select input folder
- “Replace Text” with “Copy Finder Items” to output folder before replace; Setup replace “@2x.” to “.”.
- “Scale Image” from Photos group of actions; scale to 50%
- “Reveal Finder Items” to see the result.
Your workflow has to look like this one at the right. Just press to execute and get the result in a few seconds.
So it seems working. But try to zoom the result images and you will notice inaccuracies. There are very small and thin inaccuracies with 1–2px width or height. The right one at the right. The one at the left is from Automator.
3. Photoshop
Easy to guess Photoshop is the best way to have scaled images. Except the way to design for retina and non-retina separately. The last one is hardly worth that.
As it was said it’s a “the big painful export ..”. Honestly it’s not always so. 
I usually did conversion for each file separately by pressing Cmd-Alt-Shift-S and setting Percent to 50%. It’s just about seconds but Anton (the team designer) showed me better way.
I made a video to show how simplify the whole process with Photoshop’s version of Automator – it’s called Actions (from Window > Actions) and Batch (from File > Automate > Batch).
So you may create an Action for the right scaling and execute it over the folder to get all images 1/2x scaled. And rename all images at once with Automator easily after that.
I’d like to see Apple standard solution of the problem somewhen.