JavaScript实现的图像模糊算法代码分享

var mul_table = [
        512,512,456,512,328,456,335,512,405,328,271,456,388,335,292,512,
        454,405,364,328,298,271,496,456,420,388,360,335,312,292,273,512,
        482,454,428,405,383,364,345,328,312,298,284,271,259,496,475,456,
        437,420,404,388,374,360,347,335,323,312,302,292,282,273,265,512,
        497,482,468,454,441,428,417,405,394,383,373,364,354,345,337,328,
        320,312,305,298,291,284,278,271,265,259,507,496,485,475,465,456,
        446,437,428,420,412,404,396,388,381,374,367,360,354,347,341,335,
        329,323,318,312,307,302,297,292,287,282,278,273,269,265,261,512,
        505,497,489,482,475,468,461,454,447,441,435,428,422,417,411,405,
        399,394,389,383,378,373,368,364,359,354,350,345,341,337,332,328,
        324,320,316,312,309,305,301,298,294,291,287,284,281,278,274,271,
        268,265,262,259,257,507,501,496,491,485,480,475,470,465,460,456,
        451,446,442,437,433,428,424,420,416,412,408,404,400,396,392,388,
        385,381,377,374,370,367,363,360,357,354,350,347,344,341,338,335,
        332,329,326,323,320,318,315,312,310,307,304,302,299,297,294,292,
        289,287,285,282,280,278,275,273,271,269,267,265,263,261,259];

  
var shg_table = [
         9, 11, 12, 13, 13, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 17,
        17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 18, 18, 19,
        19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 20, 20, 20,
        20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 21,
        21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
        21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22,
        22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
        22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 23,
        23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
        23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
        23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
        23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
        24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
        24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
        24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
        24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24 ];

function stackBlurImage( imageID, canvasID, radius, blurAlphaChannel )
{

     var img = document.getElementById( imageID );
    var w = img.naturalWidth;
    var h = img.naturalHeight;

    var canvas = document.getElementById( canvasID );

    canvas.style.width  = w + "px";
    canvas.style.height = h + "px";
    canvas.width = w;
    canvas.height = h;

    var context = canvas.getContext("2d");
    context.clearRect( 0, 0, w, h );
    context.drawImage( img, 0, 0 );

    if ( isNaN(radius) || radius < 1 ) return;

    if ( blurAlphaChannel )
        stackBlurCanvasRGBA( canvasID, 0, 0, w, h, radius );
    else
        stackBlurCanvasRGB( canvasID, 0, 0, w, h, radius );
}

function stackBlurCanvasRGBA( id, top_x, top_y, width, height, radius )
{
    if ( isNaN(radius) || radius < 1 ) return;
    radius |= 0;

    var canvas  = document.getElementById( id );
    var context = canvas.getContext("2d");
    var imageData;

    try {
      try {
        imageData = context.getImageData( top_x, top_y, width, height );
      } catch(e) {

    
        try {
            netscape.security.PrivilegeManager.enablePrivilege("UniversalBrowserRead");
            imageData = context.getImageData( top_x, top_y, width, height );
        } catch(e) {
            alert("Cannot access local image");
            throw new Error("unable to access local image data: " + e);
            return;
        }
      }
    } catch(e) {
      alert("Cannot access image");
      throw new Error("unable to access image data: " + e);
    }

    var pixels = imageData.data;

    var x, y, i, p, yp, yi, yw, r_sum, g_sum, b_sum, a_sum,
    r_out_sum, g_out_sum, b_out_sum, a_out_sum,
    r_in_sum, g_in_sum, b_in_sum, a_in_sum,
    pr, pg, pb, pa, rbs;

    var div = radius + radius + 1;
    var w4 = width << 2;
    var widthMinus1  = width - 1;
    var heightMinus1 = height - 1;
    var radiusPlus1  = radius + 1;
    var sumFactor = radiusPlus1 * ( radiusPlus1 + 1 ) / 2;

    var stackStart = new BlurStack();
    var stack = stackStart;
    for ( i = 1; i < div; i++ )
    {
        stack = stack.next = new BlurStack();
        if ( i == radiusPlus1 ) var stackEnd = stack;
    }
    stack.next = stackStart;
    var stackIn = null;
    var stackOut = null;

    yw = yi = 0;

    var mul_sum = mul_table[radius];
    var shg_sum = shg_table[radius];

    for ( y = 0; y < height; y++ )
    {
        r_in_sum = g_in_sum = b_in_sum = a_in_sum = r_sum = g_sum = b_sum = a_sum = 0;

        r_out_sum = radiusPlus1 * ( pr = pixels[yi] );
        g_out_sum = radiusPlus1 * ( pg = pixels[yi+1] );
        b_out_sum = radiusPlus1 * ( pb = pixels[yi+2] );
        a_out_sum = radiusPlus1 * ( pa = pixels[yi+3] );

        r_sum += sumFactor * pr;
        g_sum += sumFactor * pg;
        b_sum += sumFactor * pb;
        a_sum += sumFactor * pa;

        stack = stackStart;

        for( i = 0; i < radiusPlus1; i++ )
        {
            stack.r = pr;
            stack.g = pg;
            stack.b = pb;
            stack.a = pa;
            stack = stack.next;
        }

        for( i = 1; i < radiusPlus1; i++ )
        {
            p = yi + (( widthMinus1 < i ? widthMinus1 : i ) << 2 );
            r_sum += ( stack.r = ( pr = pixels[p])) * ( rbs = radiusPlus1 - i );
            g_sum += ( stack.g = ( pg = pixels[p+1])) * rbs;
            b_sum += ( stack.b = ( pb = pixels[p+2])) * rbs;
            a_sum += ( stack.a = ( pa = pixels[p+3])) * rbs;

            r_in_sum += pr;
            g_in_sum += pg;
            b_in_sum += pb;
            a_in_sum += pa;

            stack = stack.next;
        }

       
        stackIn = stackStart;
        stackOut = stackEnd;
        for ( x = 0; x < width; x++ )
        {
            pixels[yi+3] = pa = (a_sum * mul_sum) >> shg_sum;
            if ( pa != 0 )
            {
                pa = 255 / pa;
                pixels[yi]   = ((r_sum * mul_sum) >> shg_sum) * pa;
                pixels[yi+1] = ((g_sum * mul_sum) >> shg_sum) * pa;
                pixels[yi+2] = ((b_sum * mul_sum) >> shg_sum) * pa;
            } else {
                pixels[yi] = pixels[yi+1] = pixels[yi+2] = 0;
            }

            r_sum -= r_out_sum;
            g_sum -= g_out_sum;
            b_sum -= b_out_sum;
            a_sum -= a_out_sum;

            r_out_sum -= stackIn.r;
            g_out_sum -= stackIn.g;
            b_out_sum -= stackIn.b;
            a_out_sum -= stackIn.a;

            p =  ( yw + ( ( p = x + radius + 1 ) < widthMinus1 ? p : widthMinus1 ) ) << 2;

            r_in_sum += ( stackIn.r = pixels[p]);
            g_in_sum += ( stackIn.g = pixels[p+1]);
            b_in_sum += ( stackIn.b = pixels[p+2]);
            a_in_sum += ( stackIn.a = pixels[p+3]);

            r_sum += r_in_sum;
            g_sum += g_in_sum;
            b_sum += b_in_sum;
            a_sum += a_in_sum;

            stackIn = stackIn.next;

            r_out_sum += ( pr = stackOut.r );
            g_out_sum += ( pg = stackOut.g );
            b_out_sum += ( pb = stackOut.b );
            a_out_sum += ( pa = stackOut.a );

            r_in_sum -= pr;
            g_in_sum -= pg;
            b_in_sum -= pb;
            a_in_sum -= pa;

            stackOut = stackOut.next;

            yi += 4;
        }
        yw += width;
    }

   
    for ( x = 0; x < width; x++ )
    {
        g_in_sum = b_in_sum = a_in_sum = r_in_sum = g_sum = b_sum = a_sum = r_sum = 0;

        yi = x << 2;
        r_out_sum = radiusPlus1 * ( pr = pixels[yi]);
        g_out_sum = radiusPlus1 * ( pg = pixels[yi+1]);
        b_out_sum = radiusPlus1 * ( pb = pixels[yi+2]);
        a_out_sum = radiusPlus1 * ( pa = pixels[yi+3]);

        r_sum += sumFactor * pr;
        g_sum += sumFactor * pg;
        b_sum += sumFactor * pb;
        a_sum += sumFactor * pa;

        stack = stackStart;

        for( i = 0; i < radiusPlus1; i++ )
        {
            stack.r = pr;
            stack.g = pg;
            stack.b = pb;
            stack.a = pa;
            stack = stack.next;
        }

        yp = width;

        for( i = 1; i <= radius; i++ )
        {
            yi = ( yp + x ) << 2;

            r_sum += ( stack.r = ( pr = pixels[yi])) * ( rbs = radiusPlus1 - i );
            g_sum += ( stack.g = ( pg = pixels[yi+1])) * rbs;
            b_sum += ( stack.b = ( pb = pixels[yi+2])) * rbs;
            a_sum += ( stack.a = ( pa = pixels[yi+3])) * rbs;

            r_in_sum += pr;
            g_in_sum += pg;
            b_in_sum += pb;
            a_in_sum += pa;

            stack = stack.next;

            if( i < heightMinus1 )
            {
                yp += width;
            }
        }

        yi = x;
        stackIn = stackStart;
        stackOut = stackEnd;
        for ( y = 0; y < height; y++ )
        {
            p = yi << 2;
            pixels[p+3] = pa = (a_sum * mul_sum) >> shg_sum;
            if ( pa > 0 )
            {
                pa = 255 / pa;
                pixels[p]   = ((r_sum * mul_sum) >> shg_sum ) * pa;
                pixels[p+1] = ((g_sum * mul_sum) >> shg_sum ) * pa;
                pixels[p+2] = ((b_sum * mul_sum) >> shg_sum ) * pa;
            } else {
                pixels[p] = pixels[p+1] = pixels[p+2] = 0;
            }

            r_sum -= r_out_sum;
            g_sum -= g_out_sum;
            b_sum -= b_out_sum;
            a_sum -= a_out_sum;

            r_out_sum -= stackIn.r;
            g_out_sum -= stackIn.g;
            b_out_sum -= stackIn.b;
            a_out_sum -= stackIn.a;

            p = ( x + (( ( p = y + radiusPlus1) < heightMinus1 ? p : heightMinus1 ) * width )) << 2;

            r_sum += ( r_in_sum += ( stackIn.r = pixels[p]));
            g_sum += ( g_in_sum += ( stackIn.g = pixels[p+1]));
            b_sum += ( b_in_sum += ( stackIn.b = pixels[p+2]));
            a_sum += ( a_in_sum += ( stackIn.a = pixels[p+3]));

            stackIn = stackIn.next;

            r_out_sum += ( pr = stackOut.r );
            g_out_sum += ( pg = stackOut.g );
            b_out_sum += ( pb = stackOut.b );
            a_out_sum += ( pa = stackOut.a );

            r_in_sum -= pr;
            g_in_sum -= pg;
            b_in_sum -= pb;
            a_in_sum -= pa;

            stackOut = stackOut.next;

            yi += width;
        }
    }

    context.putImageData( imageData, top_x, top_y );

}

function stackBlurCanvasRGB( id, top_x, top_y, width, height, radius )
{
    if ( isNaN(radius) || radius < 1 ) return;
    radius |= 0;

    var canvas  = document.getElementById( id );
    var context = canvas.getContext("2d");
    var imageData;

    try {
      try {
        imageData = context.getImageData( top_x, top_y, width, height );
      } catch(e) {

 
        try {
            netscape.security.PrivilegeManager.enablePrivilege("UniversalBrowserRead");
            imageData = context.getImageData( top_x, top_y, width, height );
        } catch(e) {
            alert("Cannot access local image");
            throw new Error("unable to access local image data: " + e);
            return;
        }
      }
    } catch(e) {
      alert("Cannot access image");
      throw new Error("unable to access image data: " + e);
    }

    var pixels = imageData.data;

    var x, y, i, p, yp, yi, yw, r_sum, g_sum, b_sum,
    r_out_sum, g_out_sum, b_out_sum,
    r_in_sum, g_in_sum, b_in_sum,
    pr, pg, pb, rbs;

    var div = radius + radius + 1;
    var w4 = width << 2;
    var widthMinus1  = width - 1;
    var heightMinus1 = height - 1;
    var radiusPlus1  = radius + 1;
    var sumFactor = radiusPlus1 * ( radiusPlus1 + 1 ) / 2;

    var stackStart = new BlurStack();
    var stack = stackStart;
    for ( i = 1; i < div; i++ )
    {
        stack = stack.next = new BlurStack();
        if ( i == radiusPlus1 ) var stackEnd = stack;
    }
    stack.next = stackStart;
    var stackIn = null;
    var stackOut = null;

    yw = yi = 0;

    var mul_sum = mul_table[radius];
    var shg_sum = shg_table[radius];

    for ( y = 0; y < height; y++ )
    {
        r_in_sum = g_in_sum = b_in_sum = r_sum = g_sum = b_sum = 0;

        r_out_sum = radiusPlus1 * ( pr = pixels[yi] );
        g_out_sum = radiusPlus1 * ( pg = pixels[yi+1] );
        b_out_sum = radiusPlus1 * ( pb = pixels[yi+2] );

        r_sum += sumFactor * pr;
        g_sum += sumFactor * pg;
        b_sum += sumFactor * pb;

        stack = stackStart;

        for( i = 0; i < radiusPlus1; i++ )
        {
            stack.r = pr;
            stack.g = pg;
            stack.b = pb;
            stack = stack.next;
        }

        for( i = 1; i < radiusPlus1; i++ )
        {
            p = yi + (( widthMinus1 < i ? widthMinus1 : i ) << 2 );
            r_sum += ( stack.r = ( pr = pixels[p])) * ( rbs = radiusPlus1 - i );
            g_sum += ( stack.g = ( pg = pixels[p+1])) * rbs;
            b_sum += ( stack.b = ( pb = pixels[p+2])) * rbs;

            r_in_sum += pr;
            g_in_sum += pg;
            b_in_sum += pb;

            stack = stack.next;
        }

       
        stackIn = stackStart;
        stackOut = stackEnd;
        for ( x = 0; x < width; x++ )
        {
            pixels[yi]   = (r_sum * mul_sum) >> shg_sum;
            pixels[yi+1] = (g_sum * mul_sum) >> shg_sum;
            pixels[yi+2] = (b_sum * mul_sum) >> shg_sum;

            r_sum -= r_out_sum;
            g_sum -= g_out_sum;
            b_sum -= b_out_sum;

            r_out_sum -= stackIn.r;
            g_out_sum -= stackIn.g;
            b_out_sum -= stackIn.b;

            p =  ( yw + ( ( p = x + radius + 1 ) < widthMinus1 ? p : widthMinus1 ) ) << 2;

            r_in_sum += ( stackIn.r = pixels[p]);
            g_in_sum += ( stackIn.g = pixels[p+1]);
            b_in_sum += ( stackIn.b = pixels[p+2]);

            r_sum += r_in_sum;
            g_sum += g_in_sum;
            b_sum += b_in_sum;

            stackIn = stackIn.next;

            r_out_sum += ( pr = stackOut.r );
            g_out_sum += ( pg = stackOut.g );
            b_out_sum += ( pb = stackOut.b );

            r_in_sum -= pr;
            g_in_sum -= pg;
            b_in_sum -= pb;

            stackOut = stackOut.next;

            yi += 4;
        }
        yw += width;
    }

   
    for ( x = 0; x < width; x++ )
    {
        g_in_sum = b_in_sum = r_in_sum = g_sum = b_sum = r_sum = 0;

        yi = x << 2;
        r_out_sum = radiusPlus1 * ( pr = pixels[yi]);
        g_out_sum = radiusPlus1 * ( pg = pixels[yi+1]);
        b_out_sum = radiusPlus1 * ( pb = pixels[yi+2]);

        r_sum += sumFactor * pr;
        g_sum += sumFactor * pg;
        b_sum += sumFactor * pb;

        stack = stackStart;

        for( i = 0; i < radiusPlus1; i++ )
        {
            stack.r = pr;
            stack.g = pg;
            stack.b = pb;
            stack = stack.next;
        }

        yp = width;

        for( i = 1; i <= radius; i++ )
        {
            yi = ( yp + x ) << 2;

            r_sum += ( stack.r = ( pr = pixels[yi])) * ( rbs = radiusPlus1 - i );
            g_sum += ( stack.g = ( pg = pixels[yi+1])) * rbs;
            b_sum += ( stack.b = ( pb = pixels[yi+2])) * rbs;

            r_in_sum += pr;
            g_in_sum += pg;
            b_in_sum += pb;

            stack = stack.next;

            if( i < heightMinus1 )
            {
                yp += width;
            }
        }

        yi = x;
        stackIn = stackStart;
        stackOut = stackEnd;
        for ( y = 0; y < height; y++ )
        {
            p = yi << 2;
            pixels[p]   = (r_sum * mul_sum) >> shg_sum;
            pixels[p+1] = (g_sum * mul_sum) >> shg_sum;
            pixels[p+2] = (b_sum * mul_sum) >> shg_sum;

            r_sum -= r_out_sum;
            g_sum -= g_out_sum;
            b_sum -= b_out_sum;

            r_out_sum -= stackIn.r;
            g_out_sum -= stackIn.g;
            b_out_sum -= stackIn.b;

            p = ( x + (( ( p = y + radiusPlus1) < heightMinus1 ? p : heightMinus1 ) * width )) << 2;

            r_sum += ( r_in_sum += ( stackIn.r = pixels[p]));
            g_sum += ( g_in_sum += ( stackIn.g = pixels[p+1]));
            b_sum += ( b_in_sum += ( stackIn.b = pixels[p+2]));

            stackIn = stackIn.next;

            r_out_sum += ( pr = stackOut.r );
            g_out_sum += ( pg = stackOut.g );
            b_out_sum += ( pb = stackOut.b );

            r_in_sum -= pr;
            g_in_sum -= pg;
            b_in_sum -= pb;

            stackOut = stackOut.next;

            yi += width;
        }
    }

    context.putImageData( imageData, top_x, top_y );

}

function BlurStack()
{
    this.r = 0;
    this.g = 0;
    this.b = 0;
    this.a = 0;
    this.next = null;
}

stackBlurImage( sourceImageID, targetCanvasID, radius, blurAlphaChannel );
stackBlurCanvasRGBA( targetCanvasID, top_x, top_y, width, height, radius );
stackBlurCanvasRGB( targetCanvasID, top_x, top_y, width, height, radius );