Monday, 10 February 2014

Seven uses of the Raspberry Pi Camera

My Christmas Pi came with a 5Mp (2592x1944) f/2.9 camera module, which I intend to use as my light level sensor. I also want to use it to detect the colour of the ambient light, so that my light Things can match it.

Further along, I expect I can use it for motion detection and to recognise QR codes, car number plates and faces. And to take pictures; almost forgot. But, baby steps..

For light level and ambient colour temperature, I'd need to point the camera at a sheet of white paper.

The challenge I face is to arrange one of the following:

(a) get the exposure - which I presume corresponds to shutter speed in some way, as it's a fixed aperture - and AWB colour value, set in the EXIF

(b) disable auto-exposure and auto-AWB, and do my own sampling of the exposure to find out how much light there is, then take the average colour of the image.

(c) get the exposure and disable AWB or vice-versa, depending on the EXIF

I've been looking at the documentation and sources for information today, but it's quite hard to find what I want. For option (b), I think --shutter and --awb should allow me to set the series of shutter speeds and to turn AWB off, respectively.

It's possible that I need to do (c) - there's something in the EXIF called Light Value but I can't see a colour temperature parameter.

On Wednesday, a group of us are getting together to hack some stuff, so perhaps I'll experiment then.

PS The title today is a dig at those awful traffic-hunting titles you see these days..

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