Method to measure blurryness of photo

[CVhobbyist]

What software techniques are there for deciding if a photo is blurry or not?
I want to apply it automatically in my smartphone and discard photos which are too blurry. I'd welcome some useful keywords to search on, and also comments on how feasible and useful such a technique would be.

 

[KmH]

I'm not aware of any way to do what you want to do.

In many photos we want a goodly portion of the scene blurry.
Usually the background so the subject is 'selectively' in focus and thus visually isolated from the background an lending a sense of depth to the 2-D image.

Plus, the way optics work relative to point of focus distance, lens aperture, image sensor size, lens focal legth, etc the depth-of-field of a photograph changes as those factors change.
Understanding Depth of Field in Photography

 

[Derrel]

Maybe eliminate the taking of blurry smartphone photos, by installing an application with an anti-shake shutter interlock feature, like this one has: Camera Plus Pro- Best camera app for iPhone to shoot photos and videos

I use CameraPlus Pro's anti-shake feature whenever I want to make two or three iPhone snaps that will NOT be blurry. It works superbly, and the anti-shake interlock seems extremely well-matched to the shutter speed the phone camera is using. One of the things about the iPhone 4 that I use is that it has an f/2.8 lens, and an ISO range of 80 to 1,000, and a shutter speed that is programmed to stay wayyyyyyyyyy lower than I would like under many indoor lighting scenarios. THe camera's programming will often keep the lens at f/2.8 but drag the shutter at 1/15 second at ISO 80 or 100, instead of boosting the speed up to 1/40 second, so this app really helps.

If you use another type of phone, there is probably a similar app already on the market.

 

[CVhobbyist]

Maybe eliminate the taking of blurry smartphone photos, by installing an application with an anti-shake shutter interlock feature, like this one has: Camera Plus Pro- Best camera app for iPhone to shoot photos and videos

I use CameraPlus Pro's anti-shake feature whenever I want to make two or three iPhone snaps that will NOT be blurry. It works superbly,

Does it? Great news then, I'll start out with anti-shake. Thanx!
I was thinking about some way to measure the level of contrast in an image, but anti-shake, based on the phones motion detector, would be much easier.