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我正在尝试使用画布。我正在尝试制作一个按钮，因此当您单击它时，它会将图片更改为灰度等，这是我的代码，我不知道为什么它不起作用。

<script>
    $('#buttonID').click(function generateRGBKs( img ) {
        var w = img.width;
        var h = img.height;
        var rgbks = [];

        var canvas = document.createElement("canvas");
        canvas.width = w;
        canvas.height = h;

        var ctx = canvas.getContext("2d");
        ctx.drawImage( img, 0, 0 );

        var pixels = ctx.getImageData( 0, 0, w, h ).data;

        // 4 is used to ask for 3 images: red, green, blue and
        // black in that order.
        for ( var rgbI = 0; rgbI < 4; rgbI++ ) {
            var canvas = document.createElement("canvas");
            canvas.width  = w;
            canvas.height = h;

            var ctx = canvas.getContext('2d');
            ctx.drawImage( img, 0, 0 );
            var to = ctx.getImageData( 0, 0, w, h );
            var toData = to.data;

            for (
                    var i = 0, len = pixels.length;
                    i < len;
                    i += 4
            ) {
                toData[i  ] = (rgbI === 0) ? pixels[i  ] : 0;
                toData[i+1] = (rgbI === 1) ? pixels[i+1] : 0;
                toData[i+2] = (rgbI === 2) ? pixels[i+2] : 0;
                toData[i+3] =                pixels[i+3]    ;
            }

            ctx.putImageData( to, 0, 0 );

            // image is _slightly_ faster then canvas for this, so convert
            var imgComp = new Image();
            imgComp.src = canvas.toDataURL();

            rgbks.push( imgComp );
        }

        return rgbks;

    });


 </script>
 </head>
<body>
<img src="profile.jpg" width="400px" height="380px">
<FORM>

<INPUT TYPE="BUTTON" VALUE="Change Color" ONCLICK="buttonID" class="buttonID"> 
</FORM>
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