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View Full Version : Analyzing Brightness?

mantis2k
25th February 2010, 23:34
Is there a filter that can analyze the amount of brightness and provide a value for any given frame? I would prefer an actual number as opposed to some kind of histogram meter reading if possible please?
Tommy B.
25th February 2010, 23:42
YPlaneMinMaxDifference maybe?

http://avisynth.org/mediawiki/ConditionalFilter

edit: Nah, it's AverageLuma...

BlankClip(length=100, width=720, height=400, fps=25, color=$FFFFFF).converttoyv12().fadeio(25)

ScriptClip("Subtitle(String(AverageLuma()))")
manono
26th February 2010, 01:07
ColorYUV(Analyze=True)?
mantis2k
26th February 2010, 07:58
ColorYUV(Analyze=True)?
Is "Luma" AKA Brightness?
manono
26th February 2010, 10:36
Is "Luma" AKA Brightness?
That's a bit of a can of worms but, loosely, yes:
In video, luma represents the brightness in an image (the "black and white" or achromatic portion of the image).
http://en.wikipedia.org/wiki/Luma_(video)
StainlessS
26th February 2010, 22:50
In RGB, greys (including black & white) are made up of equal levels of all three components.
Image brightness is in eg RGB, the lowest level R or G or B in any pixel in an image.
Lets say the RGB components of the pixel with least brightness is 20,22,78
then the entire image is 'built' on top of a brightness level of 20.
Underneath that level (20) there is an underlying amount of white light (grey).
To adjust say a TV set, with an image (test card) with some black in it, you
would adjust the brightness knob until the blacks get no darker.
As Manono say though, it is a can of worms, what with Brightness, Luminance,
Value, and a host of other Color model descriptions for sort the same thing.

:)