Question

我试图通过点击色轮图像来获取RGB值。

现在我试图从下面的Color Wheel图像中获取RGB，而不使用canvas getImageData。

enter image description here

如果没有画布，我怎么能这样做？

使用画布可以运行。

$('#picker').click(function(e) { // mouse move handler

            // get coordinates of current position
            var canvasOffset = $(canvas).offset();
            var canvasX = Math.floor(e.pageX - canvasOffset.left);
            var canvasY = Math.floor(e.pageY - canvasOffset.top);

            alert("canvasX " + canvasX + " canvasY " + canvasY);

            // get current pixel
            var imageData = ctx.getImageData(canvasX, canvasY, 1, 1);
            var pixel = imageData.data;
            alert(JSON.stringify(pixel));

    });

我不能使用canvas只有这个javascript任何人都可以告诉我从图像中获取getImageData的最佳方法我需要构建一个带有for循环的rgb网格，并从x和y值中计算出所选像素然后匹配它。

真的难以在哪里开始任何帮助？

Answer 1

这是@Pointy的好主意：

只用一个色轮楔子来说明。您可以展开此起点以包含色轮中的所有楔形。

enter image description here

示例代码和演示：http://jsfiddle.net/m1erickson/9pc4orw8/

<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>

<style>
    body{ background-color: ivory; }
    #wheel{border:1px solid red;}
    #results{width:50px;height:25px;background-color:black;border:1px solid green;}
</style>

<script>
$(function(){

    var $wheel=$("#wheel");
    var wheelOffset=$wheel.offset();
    var offsetX=wheelOffset.left;
    var offsetY=wheelOffset.top;

    var PI=Math.PI;
    var cx=0;
    var cy=0;

    // define the angle & radius of each color in the color wheel
    var colors=[];
    colors.push({sAngle:0,eAngle:PI/6,sRadius:0,eRadius:15,color:'rgb(255,255,255)'});
    colors.push({sAngle:0,eAngle:PI/6,sRadius:15,eRadius:32,color:'rgb(253,237,238)'});
    colors.push({sAngle:0,eAngle:PI/6,sRadius:32,eRadius:53,color:'rgb(251,211,212)'});
    colors.push({sAngle:0,eAngle:PI/6,sRadius:53,eRadius:87,color:'rgb(246,145,149)'});
    colors.push({sAngle:0,eAngle:PI/6,sRadius:87,eRadius:117,color:'rgb(240,73,80)'});
    colors.push({sAngle:0,eAngle:PI/6,sRadius:117,eRadius:138,color:'rgb(237,27,36)'});

    $("#wheel").mousedown(function(e){handleMouseDown(e);});

    // test the current mouse position against the saved angle & radius of each color
    // return the colors index of any color under the mouse
    function hit(mx,my){
        var hitIndex=-1;
        for(var i=0;i<colors.length;i++){
            var c=colors[i];
            var a0=c.sAngle;
            var a1=c.eAngle;
            var r0=c.sRadius;
            var r1=c.eRadius;
            var dx=mx-cx;
            var dy=my-cy;
            var radius=Math.sqrt(dx*dx+dy*dy);
            var angle=Math.atan2(dy,dx);
            if(angle>a0 && angle<a1 && radius>r0 && radius<r1){
                hitIndex=i;
                break;
            }    
        }
        return(hitIndex);
    }

    function handleMouseDown(e){
        e.preventDefault();
        e.stopPropagation();

        mx=parseInt(e.clientX-offsetX);
        my=parseInt(e.clientY-offsetY);

        var colorIndex=hit(mx,my);
        if(colorIndex>=0){
            $('#results').css('background-color',colors[colorIndex].color);
        }
    }


}); // end $(function(){});
</script>
</head>
<body>
    Click to select color:<div id=results></div>
    <img id=wheel src='https://dl.dropboxusercontent.com/u/139992952/multple/colorwheel1.png'/>
</body>
</html>

获取色轮图像的RGB值

1 个答案: