Thanks Boon, I too found that it's VB which uses ^ for exponentiation.
M.
On 4/6/06, Boon Chew <[EMAIL PROTECTED]> wrote:
>
>
> ^ is xor in C and Java as well.
>
>
> elibol <[EMAIL PROTECTED]> wrote: This post is in spite of the
> discussion, I had adapted this function from
> before, but originally I decided to not post it. I liked the problem so I
> spent some time on it. I noticed Joshua that you used ^ in place of
> Math.pow,
> while ^ maybe pow in C or maybe even Java, ^ is the xor operator in
> Actionscript. So, the following code is a set of different methods to
> getting the closest color with the non-pythagoras technique preceding the
> pythagoras technique.
>
> function getClosestHex(a:Number, b:Array){
> var c=-1, d=b.length, e=768, f, a = [a>>>16, a>>>8&0x00FF,
> a&0x0000FF];
> while(++c
> Math.abs
> (a[0]-(b[c]>>>16))+Math.abs(a[1]-(b[c]>>>8&0x00FF))+Math.abs(a[2]-(b[c]&0x0000FF))
> ) )) f=c;
> return b[f];
> }
>
> var a = 0x80807f;
> var hexPalette:Array = [0x000000, 0xFFFFFF, 0xFF0000, 0x00FF00, 0x0000FF,
> 0x00FFFF, 0xFF00FF, 0xFFFF00];
> var getA = getClosestHex(a, hexPalette);
> trace(getA.toString(16));
>
> The former would be the method for hex numbers, however using RGB arrays
> is
> quicker, I found converting the palette values to RGB arrays beforehand
> would eliminate the redundancies of extracting color values, the following
> code assumes the hexPalette array in the former code is defined.
>
> function buildRGB(palette:Array){
> var a=[], i=-1, l=palette.length;
> while(++i>>16, palette[i]>>>8&0x00FF,
> palette[i]&0x0000FF];
> return a;
> }
>
> function getClosestColor(color:Array, palette:Array){
> var c=-1, d=palette.length, e=768, f;
> while(++c
> Math.abs
> (color[0]-palette[c][0])+Math.abs(color[1]-palette[c][1])+Math.abs(color[2]-palette[c][2]))))
> f=c;
> return palette[f];
> }
>
> var b = [128, 128, 127];
> var rgbPalette:Array = buildRGB(hexPalette);
> var getB = getClosestColor(b, rgbPalette);
> trace(getB);
>
> This is what the code would look like using pythagoras:
>
> function getClosestHex(a:Number, b:Array){
> var c=-1, d=b.length, e=256, f, g, h, a = [a>>>16, a>>>8&0x00FF,
> a&0x0000FF];
> while(++c
> g=0, h=-1;
> while(++h<3) g+= Math.abs(Math.pow(a[h]-(b[c]<<8<<(h*8)>>>24),
> 2));
> if(e!=(e=Math.min(e, Math.sqrt(g)))) f=c;
> }
> return b[f];
> }
>
> var b = 0x80807f;
> var hexPalette:Array = [0x000000, 0xFFFFFF, 0xFF0000, 0x00FF00, 0x0000FF,
> 0x00FFFF, 0xFF00FF, 0xFFFF00];
> var getB = getClosestHex(b, hexPalette);
> trace(getB.toString(16));
>
> function buildRGB(palette:Array){
> var a=[], i=-1, l=palette.length;
> while(++i>>16, palette[i]>>>8&0x00FF,
> palette[i]&0x0000FF];
> return a;
> }
>
> function getClosestColor(color:Array, palette:Array){
> var c=-1, d=palette.length, e=256, f, w, z, x=color.length;
> while(++c
> w=0, z=-1;
> while(++z
> if(e!=(e=Math.min( e, Math.sqrt(w)))) f=c;
> }
> return palette[f];
> }
>
> var a = [255, 128, 127];
> var hexPalette:Array = [0x000000, 0xFFFFFF, 0xFF0000, 0x00FF00, 0x0000FF,
> 0x00FFFF, 0xFF00FF, 0xFFFF00];
> var rgbPalette:Array = buildRGB(hexPalette);
> var getA = getClosestColor(a, rgbPalette);
> trace(getA);
>
> So, like Darren mentions, you could drop pythagoras and it would still be
> accurate.
>
> M.
>
> On 4/4/06, Ron Wheeler wrote:
> >
> > Another minor optimization
> >
> > Initialize tempDistance to a huge number (greater than the distance from
> > ff000 to0000ff) and then simplify the if
> >
> > Ron
> >
> > Darren Cook wrote:
> > > Hi,
> > > A minor optimization, but you can drop the Math.sqrt(). I.e.
> > > x^2 > y^2 == x > y
> > >
> > > for all positive values of x and y.
> > >
> > > Darren
> > >
> > >
> > >
> > >> That's what I actually ended up doing, and it worked out pretty good:
> > >>
> > >> private function getClosest (red1:Number, green1:Number,
> > >> blue1:Number):Number {
> > >>
> > >> var totalColors:Number = __palette.length;
> > >> var tempDistance:Number;
> > >> var closestColor:Number;
> > >>
> > >> for (var i:Number = 0; i < totalColors; i++) {
> > >> // first, break up the color to check
> > >> var red2:Number = (__palette[i] & 0xFF0000) >>> 16;
> > >> var green2:Number = (__palette[i] & 0x00FF00) >>> 8;
> > >> var blue2:Number = __palette[i] & 0x0000FF;
> > >>
> > >> // now, get the distance from the source
> > >> var tempD:Number = Math.sqrt ((Math.abs(red1 - red2) ^ 2)
> +
> > >> (Math.abs(green1 - green2) ^ 2) + (Math.abs(blue1 - blue2) ^ 2));
> > >>
> > >> if ((tempD <= tempDistance) || tempDistance == undefined)
> {
> > >> tempDistance = tempD;
> > >> closestColor = __palette[i];
> > >> }
> > >> }
> > >>
> > >> return closestColor;
> > >> }
> > >>
> > >>
> > >> - Josh
> > >>
> > >>
> > >> On Mar 16, 2006, at 7:59 PM, Ron Wheeler wrote:
> > >>
> > >>
> > >>> If a color can be treated as a point in a 3-d cube 256 units
> on each
> > >>> side, you can use the formula in this reference
> > >>> http://www.uwm.edu/~ericskey/TANOTES/Ageometry/node10.html
> > >>> to calculate the "distance" between 2 colors.
> > >>>
> > >>> I have not tried this but it would seem logical that this would work
> > >>>
> > >>> Ron
> > >>>
> > >>> elibol wrote:
> > >>>
> > >>>
> > >>>> K, here is some better math for getRGB, performance will probably
> be
> > >>>> important:
> > >>>>
> > >>>> return [c>>>16, c>>8&~0xFF00, c&~0xFFFFF00];
> > >>>>
> > >>>> You can also try using the ColorTransform or Color class to
> get the
> > rgb
> > >>>> values, except they might be slower than getting the raw math
> right.
> > >>>>
> > >>>> M.
> > >>>>
> > >>>> On 3/15/06, Josh Buhler wrote:
> > >>>>
> > >>>>
> > >>>>> Thanks - I'll give it a shot and see how it goes.
> > >>>>>
> > >>>>>
> > >>>>> - Josh
> > >>>>>
> > >>>>> On Mar 15, 2006, at 3:10 PM, elibol wrote:
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>>> I tried comparing the hex values directly, but there were
> > >>>>>> inaccuracies,
> > >>>>>> maybe the same ones you've been having. I think since the
> value of
> > a
> > >>>>>> particular color precedes with a 0 even when it's below 17(0F),
> the
> > >>>>>> preceding 0 causes a shifting in the comparison. It would, for
> > >>>>>> example,
> > >>>>>> cause 0x000000 to seem farther to 0x123456 than 0x00FF00, where
> > >>>>>> visually you
> > >>>>>> can see clearly that black is closer to 0x000000.
> > >>>>>>
> > >>>>>> btw in my example, var a = 0x12345 where it should be 0x123456.
> > >>>>>>
> > >>>>>> The numbers hold to be accurate after correcting this typo.
> > >>>>>>
> > >>>>>> On 3/15/06, Josh Buhler wrote:
> > >>>>>>
> > >>>>>>
> > >>>>>>> I'm working on a project that requires that I take an uploaded
> > >>>>>>> image,
> > >>>>>>> and convert it to use a limited palette of colors - around 5-10
> > >>>>>>> colors.
> > >>>>>>>
> > >>>>>>> I've got the custom palette I have to work with stored in
> > an array,
> > >>>>>>> and for each color in my image, I've got it finding the
> color in
> > the
> > >>>>>>> array it's closest to numerically, but the results aren't
> exactly
> > >>>>>>> what I'm looking for.
> > >>>>>>>
> > >>>>>>> Does anybody know of any formulas available for comparing
> multiple
> > >>>>>>> colors and finding the ones that are the closest matches?
> > I've been
> > >>>>>>> searching Google for a while, with no luck. Any good resources
> on
> > >>>>>>> color formulas & such would be appreciated.
> > >>>>>>>
> > >>>>>>> - Josh
> > >>>>>>> _______________________________________________
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