Pixel brightness question

[sebgg]

hi all

ok so my problem is i need to find a way to get autoit to check the brightness of a given pixel.

and by brightness I mean purley how light or dark it is on a grey scale.

i have written a script to check pixel color, and was wondering if:

a) there is one for brightness

(more likley) i can convert the output, either hexadecimal etc into something which gives how light or dark that particular pixel is, as i am not interested in color at all.

so it there something about a hexadecimal code for a color, which is analagous to brightness?

thanks in advance

sebs

[Melba23]

sebgg,

The standard (according to Google) method to determine the "luminosity" of a given colour is to use the following formula:

(Red_Value * 0.3) + (Green_Value * 0.59) + (Blue_Value * 0.11)

So as you have the pixel colour, all you need to do is to plug in the return values from _ColorGetRed, _ColorGetGreen and _ColorGetBlue into that formula and you have your result on a scale of 0 to 255.

I have used a very similar process to greyscale images with GDI with excellent results.

M23

[jvanegmond]

(Red_Value * 0.3) + (Green_Value * 0.59) + (Blue_Value * 0.11)

M23

I found this StackOverflow topic which gives a bit more detail: http://stackoverflow.com/questions/596216/formula-to-determine-brightness-of-rgb-color

Digital CCIR601 is a lot like the one you posted.

Edited October 11, 2010 by Manadar

[Melba23]

Manadar,

Thanks for that link - obviously a more complex matter than suggested by the searches I made when I was writing my greyscale script a while ago. But I think I will just stick with my simplistic version - the results were good enough for me.

M23

[Ascend4nt]

Check out the API call 'ColorRGBToHLS', which will give you non-floating-point results. You'll need to shift the color to a 'BGR' format first, but this is easy enough to do.

[sebgg]

thanks all for the info, have gone for the basic one as im not too hot at this and it seems to work ok

thanks again

sebs