[转]是把一张图片中除白色之外的其他像素都变为黑色

查API的时候查到一个ColorTransform类，觉得这个类应该可以完成我需要的功能，不过现在还是想不到应该怎么样才能实现这个需求


哈哈，谢谢！
功能实现了，经你一提醒，我试了一下把MC的饱和度和亮度都设为－100，差不多就是我想要的效果

代码如下：

var color:ColorMatrix = new ColorMatrix();
color.adjustSaturation(-100);
color.adjustBrightness(-100);
mc.filters = [new ColorMatrixFilter(color)];

以下是ColorMatrix类（此类是他人作品，使用请加上作者信息，谢谢！）:
/**
* ColorMatrix by Grant Skinner. August 8, 2005
* Updated to AS3 November 19, 2007
* Visit www.gskinner.com/blog for documentation, updates and more free code.
*
* You may distribute this class freely, provided it is not modified in any way (including
* removing this header or changing the package path).
*
* Please contact [e-mail] prior to distributing modified versions of this class.

*usage:http://www.gskinner.com/blog/archives/2005/09/flash_8_source.html

*var cm = new ColorMatrix();
* cm.adjustColor(20,20,20,20);
*displayObject.filters = [new ColorMatrixFilter(cm)];
*/

package 
{

    dynamic public class ColorMatrix extends Array
    {

// constant for contrast calculations:
        private static const DELTA_INDEX:Array = [
            0,    0.01, 0.02, 0.04, 0.05, 0.06, 0.07, 0.08, 0.1, 0.11,
            0.12, 0.14, 0.15, 0.16, 0.17, 0.18, 0.20, 0.21, 0.22, 0.24,
            0.25, 0.27, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.42,
            0.44, 0.46, 0.48, 0.5, 0.53, 0.56, 0.59, 0.62, 0.65, 0.68, 
            0.71, 0.74, 0.77, 0.80, 0.83, 0.86, 0.89, 0.92, 0.95, 0.98,
            1.0, 1.06, 1.12, 1.18, 1.24, 1.30, 1.36, 1.42, 1.48, 1.54,
            1.60, 1.66, 1.72, 1.78, 1.84, 1.90, 1.96, 2.0, 2.12, 2.25, 
            2.37, 2.50, 2.62, 2.75, 2.87, 3.0, 3.2, 3.4, 3.6, 3.8,
            4.0, 4.3, 4.7, 4.9, 5.0, 5.5, 6.0, 6.5, 6.8, 7.0,
            7.3, 7.5, 7.8, 8.0, 8.4, 8.7, 9.0, 9.4, 9.6, 9.8, 
            10.0
           ];

        // identity matrix constant:
        private static const IDENTITY_MATRIX:Array = [
            1,0,0,0,0,
            0,1,0,0,0,
            0,0,1,0,0,
            0,0,0,1,0,
            0,0,0,0,1
           ];
        private static const LENGTH:Number = IDENTITY_MATRIX.length;


// initialization:
        public function ColorMatrix(p_matrix:Array = null)
        {
            p_matrix = fixMatrix(p_matrix);
            copyMatrix(((p_matrix.length == LENGTH) ? p_matrix : IDENTITY_MATRIX));
        }


// public methods:
        public function reset():void
        {
            for (var i:uint = 0; i < LENGTH; i++)
            {
                this[i] = IDENTITY_MATRIX[i];
            }
        }

        public function adjustColor(p_brightness:Number, p_contrast:Number, p_saturation:Number, p_hue:Number):void
        {
            adjustHue(p_hue);
            adjustContrast(p_contrast);
            adjustBrightness(p_brightness);
            adjustSaturation(p_saturation);
        }

        public function adjustBrightness(p_val:Number):void   {
            p_val = cleanValue(p_val, 100);
            if (p_val == 0 || isNaN(p_val))
            {
                return;
            }
             multiplyMatrix([
                 1,0,0,0,p_val,
                 0,1,0,0,p_val,
                 0,0,1,0,p_val,
                 0,0,0,1,0,
                 0,0,0,0,1
                ]);
        }

        public function adjustContrast(p_val:Number):void
        {
            p_val = cleanValue(p_val, 100);
            if (p_val == 0 || isNaN(p_val))
            {
                return;
            }
            var x:Number;
            if (p_val < 0)
            {
                x = 127 + p_val / 100 * 127;
            }
            else
            {
                x = p_val % 1;
                if (x == 0)
                {
                    x = DELTA_INDEX[p_val];
                }
                else
                {
                    //x = DELTA_INDEX[(p_val<<0)]; // this is how the IDE does it.
                    x = DELTA_INDEX[(p_val << 0)] * (1 - x) + DELTA_INDEX[(p_val << 0) + 1] * x; // use linear interpolation for more granularity.
                }
                x = x * 127 + 127;
            }
            multiplyMatrix([
                 x/127,0,0,0,0.5*(127-x),
                 0,x/127,0,0,0.5*(127-x),
                 0,0,x/127,0,0.5*(127-x),
                 0,0,0,1,0,
                 0,0,0,0,1
                ]);

        }

        public function adjustSaturation(p_val:Number):void
        {
            p_val = cleanValue(p_val, 100);
            if (p_val == 0 || isNaN(p_val))
            {
                return;
            }
            var x:Number = 1 + ((p_val > 0) ? 3 * p_val / 100 : p_val / 100);
            var lumR:Number = 0.3086;
            var lumG:Number = 0.6094;
            var lumB:Number = 0.0820;
            multiplyMatrix([
                 lumR*(1-x)+x,lumG*(1-x),lumB*(1-x),0,0,
                 lumR*(1-x),lumG*(1-x)+x,lumB*(1-x),0,0,
                 lumR*(1-x),lumG*(1-x),lumB*(1-x)+x,0,0,
                 0,0,0,1,0,
                 0,0,0,0,1
                ]);

        }

        public function adjustHue(p_val:Number):void
        {
            p_val = cleanValue(p_val, 180) / 180 * Math.PI;
            if (p_val == 0 || isNaN(p_val))
            {
                return;
            }
            var cosVal:Number = Math.cos(p_val);
            var sinVal:Number = Math.sin(p_val);
            var lumR:Number = 0.213;
            var lumG:Number = 0.715;
            var lumB:Number = 0.072;
            multiplyMatrix([
                 lumR+cosVal*(1-lumR)+sinVal*(-lumR),lumG+cosVal*(-lumG)+sinVal*(-lumG),lumB+cosVal*(-lumB)+sinVal*(1-lumB),0,0,
                 lumR+cosVal*(-lumR)+sinVal*(0.143),lumG+cosVal*(1-lumG)+sinVal*(0.140),lumB+cosVal*(-lumB)+sinVal*(-0.283),0,0,
                 lumR+cosVal*(-lumR)+sinVal*(-(1-lumR)),lumG+cosVal*(-lumG)+sinVal*(lumG),lumB+cosVal*(1-lumB)+sinVal*(lumB),0,0,
                 0,0,0,1,0,
                 0,0,0,0,1
                ]);

        }

        public function concat(p_matrix:Array):void
        {
            p_matrix = fixMatrix(p_matrix);
            if (p_matrix.length != LENGTH)
            {
                return;
            }
            multiplyMatrix(p_matrix);
        }

        public function clone():ColorMatrix
        {
            return new ColorMatrix(this);
        }

        public function toString():String
        {
            return "ColorMatrix [ " + this.join(" , ") + " ]";
        }

        // return a length 20 array (5x4):
        public function toArray():Array
        {
            return slice(0, 20);
        }

// private methods:
        // copy the specified matrix's values to this matrix:
        protected function copyMatrix(p_matrix:Array):void
        {
            var l:Number = LENGTH;
            for (var i:uint = 0; i < l; i++)
            {
                this[i] = p_matrix[i];
            }
        }

        // multiplies one matrix against another:
        protected function multiplyMatrix(p_matrix:Array):void
        {
            var col:Array = [];

            for (var i:uint = 0; i < 5; i++)
            {
                for (var j:uint = 0; j < 5; j++)
                {
                    col[j] = this[j + i * 5];
                }
                for (j = 0; j < 5; j++)
                {
                    var val:Number = 0;
                    for (var k:Number = 0; k < 5; k++)
                    {
                        val += p_matrix[j + k * 5] * col[k];
                    }
                    this[j + i * 5] = val;
                }
            }
        }

        // make sure values are within the specified range, hue has a limit of 180, others are 100:
        protected function cleanValue(p_val:Number, p_limit:Number):Number
        {
            return Math.min(p_limit, Math.max(-p_limit, p_val));
        }

        // makes sure matrixes are 5x5 (25 long):
        protected function fixMatrix(p_matrix:Array = null):Array
        {
            if (p_matrix == null)
            {
                return IDENTITY_MATRIX;
            }
            if (p_matrix is ColorMatrix)
            {
                p_matrix = p_matrix.slice(0);
            }
            if (p_matrix.length < LENGTH)
            {
                p_matrix = p_matrix.slice(0, p_matrix.length).concat(IDENTITY_MATRIX.slice(p_matrix.length, LENGTH));
            }
            else if (p_matrix.length > LENGTH)
            {
                p_matrix = p_matrix.slice(0, LENGTH);
            }
            return p_matrix;
        }
    }
}