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canvas绘制饼图

分类：图表日期：2024-05-14 点击(9) 评论(0)

canvas绘制饼图

简介

#### html
```html
 <canvas id="canvas_circle" width="500" height="300" >
        浏览器不支持canvas
    </canvas>
```
#### js
```html
function drawCircle(canvasId, data_arr, color_arr, text_arr)
        {
            //初始化数据 
            var c = document.getElementById(canvasId);
            var ctx = c.getContext("2d");
            var radius = c.height / 2 - 20; //半径
            var ox = radius + 20, oy = radius + 20; //圆心
            var width = 30, height = 10; //图例宽和高
            var posX = ox * 2 + 20, posY = 30;   //
            var textX = posX + width + 5, textY = posY + 10;
            var startAngle = 0; //起始弧度
            var endAngle = 0;   //结束弧度

//将传入的数据转化百分比
            var totleNb = 0;
            var new_data_arr = [];
            for (var i = 0; i < data_arr.length; i++){
                totleNb += data_arr[i];
            }
            for (var i = 0; i < data_arr.length; i++){
                new_data_arr.push( data_arr[i]/totleNb );
            }

//绘制比例图及文字
            for (var i = 0; i < data_arr.length; i++){
                //绘制比例图及文字
                ctx.fillStyle = color_arr[i];
                ctx.fillRect(posX, posY + 20 * i, width, height);
                ctx.moveTo(posX, posY + 20 * i);
                ctx.font = 'bold 12px 微软雅黑';    //斜体 30像素 微软雅黑字体
                ctx.fillStyle = color_arr[i]; //"#000000";
                var percent = text_arr[i] + "：" + parseInt(100 * new_data_arr[i]) + "%";
                ctx.fillText(percent, textX, textY + 20 * i);
            }

//利用定时器实现绘制动画
            var iNow = 0;
            var moveNomber = 50;
            var timer = null;
            pieDraw();
            function pieDraw(mousePosition){
                clearInterval(timer);
                timer = setInterval(function(){
                    iNow++;
                    console.log(iNow);

if(mousePosition){
                        clearInterval(timer);
                        iNow = moveNomber;
                    }else if(iNow>moveNomber){
                        clearInterval(timer);
                        timer = null;
                        return false;
                    }

//先清除一下图
                    ctx.clearRect(0, 0, ox * 2 + 20, oy * 2 + 20);

for (var j = 0; j < data_arr.length; j++){
                        //绘制饼图
                        endAngle = endAngle + new_data_arr[j]* iNow/moveNomber * Math.PI * 2; //结束弧度
                        ctx.fillStyle = color_arr[j];
                        ctx.beginPath();
                        ctx.moveTo(ox, oy); //移动到到圆心
                        ctx.arc(ox, oy, radius, startAngle, endAngle, false); //
                        console.log(mousePosition, mousePosition && ctx.isPointInPath(mousePosition.x, mousePosition.y));
                        if(mousePosition && ctx.isPointInPath(mousePosition.x, mousePosition.y)){
                            ctx.moveTo(ox, oy);
                            ctx.arc(ox, oy, radius+5, startAngle, endAngle, false);
                        }

ctx.closePath();
                        ctx.fill();

startAngle = endAngle; //设置起始弧度
                        if( j == data_arr.length-1 ){
                            startAngle = 0;
                            endAngle = 0;
                        }
                    }

},10);
            }

//监听鼠标移动
            var mouseTimer = null;
            c.addEventListener("mousemove",function(e){
                var mousePosition = {};
                e = e || window.event;
                if( e.layerX || e.layerX==0 ){
                    mousePosition.x = e.layerX;
                    mousePosition.y = e.layerY;
                }else if( e.offsetX || e.offsetX==0 ){
                    mousePosition.x = e.offsetX;
                    mousePosition.y = e.offsetY;
                }
                //console.log(mousePosition);
                clearTimeout(mouseTimer);
                mouseTimer = setTimeout(function(){
                    pieDraw(mousePosition);
                },20);
            });

}
        function init() {
            //绘制饼图
            //比例数据和颜色
            var data_arr = [50, 750, 100, 200];
            var color_arr = ["#00a000", "#00AABB", "#FFAA00", "#FF4400"];
            var text_arr = ["第一季度", "第二季度", "第三季度", "第四季度"];
            drawCircle("canvas_circle", data_arr, color_arr, text_arr);

}
        //页面加载时执行init()函数
        window.onload = init;
```

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canvas绘制饼图

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