josiah47
Member
Okay, I have a little project that I can't give the full details but, basically what I need to do is get a camera hooked up to the Maple and then make it look at a scene, take the average brightness of the scene, so pixel by pixel calculation and then send the average brightness to the pc via serial.
Any clues on how to go about this,
camera choice? anyone currently using a camera with the controller?
code to do the numbering crunching?
Thanks
robodude666
Member
Why would you use a camera to get the brightness of a scene? Use a camera to take a picture. Use an ambient light sensor or LDR to determine the brightness in an area. Alas, as for cameras.. I know SparkFun has a LinkSprite TTL camera, but it captures JPEG images. You may need a camera that gets raw values. The 4D Systems µCAM-TTL claims to offer RAW RGB modes.
Once you get your camera to communicate with the Maple, look at the RGB value of every pixel and calculate the luminance. Sum them up and divide by the number of pixels to get the average luminance of the entire picture. You'll be doing a lot of math, so I'd recommend taking a look at libfixmath to help with all those calculations.
gbulmer
Moderator
josiah47 - are you willing to try to program the camera?
If you are, look at Canon Hack Development Kit
http://chdk.wikia.com/wiki/CHDK
In theory, with the right Canon camera, you could do everything in the camera. There are some advantages to this, including a faster processor, and plenty of RAM. Also, no need for anything except a camera. I picked up some Canon cameras at a reasonable price on eBay.
josiah47
Member
well im hoping i do not need to use a camera since a ambient light sensor might work, but if one part of the scene is darker and another lighter i don't know if the ambient light will sense that i guess it will since its an average, i think maybe ill test it first.
poslathian
LeafLabs
You can use an array of ambient sensors (as few as two...) and use the differential readings to determine the gradient of the ambient light (what direction is brighter/darker).
The canonical example of this is a drive-towards-the-light robot. Take two take two ambient light sensors on a little horizontal bar. Put a small piece of cardboard in the middle to separate them, then turn your robot towards whichever sensor has the lower output.
Not sure what you are doing, but if you just need to know what part of the scene is light/dark, you can play tricks like this. 3 ambient light sensors and you should be able to triangulate the center of mass of the lighting input.
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