Flash's smoothing may introduce irregularities, I guess.
But given that the original poster only wanted to know grey or white,
surely it's a good enough approximation for that purpose?
Ian
On Sun, Mar 29, 2009 at 9:08 PM, Juan Pablo Califano
<califa010.flashcod...@gmail.com> wrote:
> It's indeed much faster (five times faster than transforming to grey scale),
> though the results I'm getting are incorrect (the other 2 methods seems to
> return consistently similar results, though trasnforming to HLS takes about
> 3200 ms for a 1152 x 864 image, and transform to grey scale takes around 130
> ms).
>
> It could be the case that I'm doing it the wrong way, of course... This is
> the code I'm using.
>
>
> function getAverageFromScaledBitmap(src:DisplayObject):Number {
> var dest:BitmapData = new BitmapData(1,1);
> var mat:Matrix = new Matrix();
> var sx:Number = 1 / src.width;
> var sy:Number = 1 / src.height;
>
> mat.scale(sx,sy);
> dest.draw(src,mat,null,null,null,true);
> var hls:Object = ColorUtils.RGBtoHLS(dest.getPixel(0,0));
>
> return hls.l;
> }
> Cheers
> Juan Pablo Califano
>
> 2009/3/29 Ian Thomas <i...@eirias.net>
>
>> On Sun, Mar 29, 2009 at 8:14 PM, Juan Pablo Califano
>> <califa010.flashcod...@gmail.com> wrote:
>> > As it's been said already, you could try converting to HLS and the get
>> the
>> > average luminance (brigthness). Here's a handy class to convert from RGB
>> to
>> > HSL and viceversa.
>> >
>> > http://www.dreaminginflash.com/2007/11/19/hls-to-rgb-rgb-to-hls/
>> > Another approach, which might be faster (but you'd have to test it to see
>> if
>> > that's true), could be transforming to bitmap to a grey scale. You would
>> > then know how black / white each pixel is, so you could get the average
>> > value by adding the value of each pixel and dividing for the total number
>> of
>> > pixels. Instead of reading the whole pixel value, you can just read one
>> > channel, because since it' s a grey scale, the three color channels will
>> be
>> > equal.
>>
>> If you're going to test any kind of average pixel value, it'd be far
>> faster to take a bitmap copy of the frame scaled to 1 pixel x 1 pixel
>> (with smoothing on) - and just read the colour value of that pixel...
>>
>> HTH,
>> Ian
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