在这个demo中将使用html5 canvas和jQuery来制作一个动态的饼状图表。

HTML

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Click a colour in the chart, or an item in the table, to pull out a slice! Back to Tutorial

HTML结构非常简单，它包括：

一个container作为包裹容器。

一个用于绘制饼状图的HTML5 canvas。

一个表格用于放置图表数据。

配置图表函数、参数和可用变量

// Run the code when the DOM is ready

$( pieChart );

function pieChart() {

// Config settings

var chartSizePercent = 55; // The chart radius relative to the canvas width/height (in percent)

var sliceBorderWidth = 1; // Width (in pixels) of the border around each slice

var sliceBorderStyle = "#fff"; // Colour of the border around each slice

var sliceGradientColour = "#ddd"; // Colour to use for one end of the chart gradient

var maxPullOutDistance = 25; // How far, in pixels, to pull slices out when clicked

var pullOutFrameStep = 4; // How many pixels to move a slice with each animation frame

var pullOutFrameInterval = 40; // How long (in ms) between each animation frame

var pullOutLabelPadding = 65; // Padding between pulled-out slice and its label

var pullOutLabelFont = "bold 16px 'Trebuchet MS', Verdana, sans-serif"; // Pull-out slice label font

var pullOutValueFont = "bold 12px 'Trebuchet MS', Verdana, sans-serif"; // Pull-out slice value font

var pullOutValuePrefix = "$"; // Pull-out slice value prefix

var pullOutShadowColour = "rgba( 0, 0, 0, .5 )"; // Colour to use for the pull-out slice shadow

var pullOutShadowOffsetX = 5; // X-offset (in pixels) of the pull-out slice shadow

var pullOutShadowOffsetY = 5; // Y-offset (in pixels) of the pull-out slice shadow

var pullOutShadowBlur = 5; // How much to blur the pull-out slice shadow

var pullOutBorderWidth = 2; // Width (in pixels) of the pull-out slice border

var pullOutBorderStyle = "#333"; // Colour of the pull-out slice border

var chartStartAngle = -.5 * Math.PI; // Start the chart at 12 o'clock instead of 3 o'clock

// Declare some variables for the chart

var canvas; // The canvas element in the page

var currentPullOutSlice = -1; // The slice currently pulled out (-1 = no slice)

var currentPullOutDistance = 0; // How many pixels the pulled-out slice is currently pulled out in the animation

var animationId = 0; // Tracks the interval ID for the animation created by setInterval()

var chartData = []; // Chart data (labels, values, and angles)

var chartColours = []; // Chart colours (pulled from the HTML table)

var totalValue = 0; // Total of all the values in the chart

var canvasWidth; // Width of the canvas, in pixels

var canvasHeight; // Height of the canvas, in pixels

var centreX; // X-coordinate of centre of the canvas/chart

var centreY; // Y-coordinate of centre of the canvas/chart

var chartRadius; // Radius of the pie chart, in pixels

// Set things up and draw the chart

init();

初始化图表

/**

* Set up the chart data and colours, as well as the chart and table click handlers,

* and draw the initial pie chart

*/

function init() {

// Get the canvas element in the page

canvas = document.getElementById('chart');

// Exit if the browser isn't canvas-capable

if ( typeof canvas.getContext === 'undefined' ) return;

// Initialise some properties of the canvas and chart

canvasWidth = canvas.width;

canvasHeight = canvas.height;

centreX = canvasWidth / 2;

centreY = canvasHeight / 2;

chartRadius = Math.min( canvasWidth, canvasHeight ) / 2 * ( chartSizePercent / 100 );

// Grab the data from the table,

// and assign click handlers to the table data cells

var currentRow = -1;

var currentCell = 0;

$('#chartData td').each( function() {

currentCell++;

if ( currentCell % 2 != 0 ) {

currentRow++;

chartData[currentRow] = [];

chartData[currentRow]['label'] = $(this).text();

} else {

var value = parseFloat($(this).text());

totalValue += value;

value = value.toFixed(2);

chartData[currentRow]['value'] = value;

}

// Store the slice index in this cell, and attach a click handler to it

$(this).data( 'slice', currentRow );

$(this).click( handleTableClick );

// Extract and store the cell colour

if ( rgb = $(this).css('color').match( /rgb\((\d+), (\d+), (\d+)/) ) {

chartColours[currentRow] = [ rgb[1], rgb[2], rgb[3] ];

} else if ( hex = $(this).css('color').match(/#([a-fA-F0-9]{2})([a-fA-F0-9]{2})([a-fA-F0-9]{2})/) ) {

chartColours[currentRow] = [ parseInt(hex[1],16) ,parseInt(hex[2],16), parseInt(hex[3], 16) ];

} else {

alert( "Error: Colour could not be determined! Please specify table colours using the format '#xxxxxx'" );

return;

}

} );

// Now compute and store the start and end angles of each slice in the chart data

var currentPos = 0; // The current position of the slice in the pie (from 0 to 1)

for ( var slice in chartData ) {

chartData[slice]['startAngle'] = 2 * Math.PI * currentPos;

chartData[slice]['endAngle'] = 2 * Math.PI * ( currentPos + ( chartData[slice]['value'] / totalValue ) );

currentPos += chartData[slice]['value'] / totalValue;

}

// All ready! Now draw the pie chart, and add the click handler to it

drawChart();

$('#chart').click ( handleChartClick );

}