Get Light Level from Camera

[rfj]

I am doing home automation (using HomeSeer) and for many actions depend on the light level. For indoor I have plugin light sensors but outside I would have to use wireless sensors. Hence, I was wondering if the cameras could be used as light sensors? I don't think cameras provide any LUX measurements (though that would be cool) but maybe pixel values, gain, aperture and shutter speed are embedded into the images. If so, is there a way to retrieve that from BlueIris to calculate some light value?

 

[jaydeel]

I've successfully used the algorithm provided below to test the brightness (or darkness) of a camera image.
In the past I used it to automate the toggling of backlight mode for a camera in a challenging environment.

source

function getBrightness($gdHandle) {
    $width = imagesx($gdHandle);
    $height = imagesy($gdHandle);
    $totalBrightness = 0;
    $precise=5; /lower is more precise but slower
    for ($x = 0; $x < $width; $x+=$precise) {
        for ($y = 0; $y < $height; $y+=$precise) {
            $rgb = imagecolorat($gdHandle, $x, $y);
            $red = ($rgb >> 16) & 0xFF;
            $green = ($rgb >> 8) & 0xFF;
            $blue = $rgb & 0xFF;
            $totalBrightness += (max($red, $green, $blue) + min($red, $green, $blue)) / 2;
        }
    }
    imagedestroy($gdHandle);
    return ($totalBrightness / (($width/$precise) * ($height/$precise))) / 2.55;

/ USAGE $var=getBrightness(imagecreatefromjpeg('pic1.jpg'));

Here are several more helpful references used in my project:

How to detect "light" colors with PHP

I am working on a dynamic store project and I use a loop to print all color options for a product as color boxes, however I really need to add a "border" to these colors which are light. I tried

stackoverflow.com

Image creator: Dynamic Dummy Image Generator - DummyImage.com ... used to create test WxH jpgs filled with single color

 

[SpacemanSpiff]

Any way to leverage the functionality of this algorithm to switch individual, or a group of cameras to night mode?

Several indoor cameras in a space that is dark unless it is occupied. This might be a great utility for the task