html5 canvas 画图表

(function () {
    var canvas = document.createElement("canvas");
    canvas.width = 800;
    canvas.height = 400;
    canvas.innerText = "抱歉，你的浏览器不支持canvas T_T";
    document.getElementById(‘leoncanvas‘).appendChild(canvas);

    var data = { "aaa": 1000, "bbb": 600, "ccc": 200, "ddd": 400, "eee": 550, "fff": 50, "ggg": 10, "hhh": 280 };
    var yAxisValueStep = 100;

    var width = canvas.width;
    var height = canvas.height;

    // data length calc & value analysis
    var length = 0, min = 0, max = 0;

    for (var i in data) {
        length++;
        if (data[i] < min)
            min = data[i];
        if (data[i] > max)
            max = data[i];
    }

    var xLength = width * 0.9;
    var yLength = height * 0.7;
    var left = width * 0.12;
    var bottom = height * 0.08;

    // origin point
    var x0 = left;
    var y0 = height - bottom;

    var p0 = { x: x0, y: y0 };
    var px = { x: left + xLength, y: p0.y };
    var py = { x: p0.x, y: p0.y - yLength };

    var xScaleMarkWidth = xLength / (length + 3);
    var yScaleMarkWidth = yLength / (length + 3);

    // begin to draw axis
    var context = canvas.getContext(‘2d‘);
    context.beginPath();
    // offset 0.5 to draw 1 pixel line
    //http://kilianvalkhof.com/2010/design/the-problem-with-svg-and-canvas/
    // xAxis
    context.moveTo(p0.x + 0.5, p0.y + 0.5);
    context.lineTo(px.x + 0.5, px.y + 0.5);
    // yAxis
    context.moveTo(p0.x + 0.5, p0.y + 0.5);
    context.lineTo(py.x + 0.5, py.y + 0.5);

    context.font = "normal lighter 12px sans-serif";

    // scale marker
    for (var i = 0; i < length + 2; i++) {
        // xaxis
        context.moveTo(p0.x + (i + 1) * xScaleMarkWidth + 0.5, p0.y + 0.5);
        context.lineTo(p0.x + (i + 1) * xScaleMarkWidth + 0.5, p0.y + 2 + 0.5);

        // yaxis
        context.moveTo(p0.x + 0.5, p0.y - (i + 1) * yScaleMarkWidth + 0.5);
        context.lineTo(p0.x + 0.5 - 2, p0.y - (i + 1) * yScaleMarkWidth + 0.5);
    }

    // y axis marker value
    for (var i = 0; i <= length + 2; i++) {
        // yaxis value
        context.fillText(yAxisValueStep * i, p0.x + 0.5 - 30, p0.y - i * yScaleMarkWidth + 3);
    }

    // draw column chart
    var lengthPerValue = (yScaleMarkWidth * (length + 2)) / max;
    var rectX, rectY;
    var i = 0;

    for (var p in data) {
        rectX = p0.x + (i + 1) * xScaleMarkWidth + 0.5 - xScaleMarkWidth * 0.25;
        rectY = p0.y - lengthPerValue * data[p];

        // draw column
        context.fillStyle = "rgba(255,0,0,0.6)";
        context.fillRect(rectX, rectY, xScaleMarkWidth / 2, lengthPerValue * data[p]);

        // add text
        context.fillStyle = ‘rgb(0,0,0)‘;
        // column value
        context.fillText(data[p], rectX, rectY - 15);
        // x value
        context.fillText(p, rectX + xScaleMarkWidth * 0.1, rectY + lengthPerValue * data[p] + 20);
        i++;
    }

    context.lineWidth = 1;
    context.stroke();
    context.closePath();
})();

(function () {
    var canvas = document.createElement("canvas");
    canvas.width = 800;
    canvas.height = 400;
    canvas.innerText = "抱歉，你的浏览器不支持canvas T_T";
    document.getElementById(‘leoncanvas1‘).appendChild(canvas);

    var data = { "aaa": 1000, "bbb": 600, "ccc": 200, "ddd": 400, "eee": 550, "fff": 50, "ggg": 10, "hhh": 280 };
    var yAxisValueStep = 100;

    var width = canvas.width;
    var height = canvas.height;

    // data length calc & value analysis
    var length = 0, min = 0, max = 0;

    for (var i in data) {
        length++;
        if (data[i] < min)
            min = data[i];
        if (data[i] > max)
            max = data[i];
    }

    var xLength = width * 0.9;
    var yLength = height * 0.7;
    var left = width * 0.12;
    var bottom = height * 0.08;

    // origin point
    var x0 = left;
    var y0 = height - bottom;

    var p0 = { x: x0, y: y0 };
    var px = { x: left + xLength, y: p0.y };
    var py = { x: p0.x, y: p0.y - yLength };

    var xScaleMarkWidth = xLength / (length + 3);
    var yScaleMarkWidth = yLength / (length + 3);

    // begin to draw axis
    var context = canvas.getContext(‘2d‘);
    context.beginPath();
    // offset 0.5 to draw 1 pixel line
    //http://kilianvalkhof.com/2010/design/the-problem-with-svg-and-canvas/
    // xAxis
    context.moveTo(p0.x + 0.5, p0.y + 0.5);
    context.lineTo(px.x + 0.5, px.y + 0.5);
    // yAxis
    context.moveTo(p0.x + 0.5, p0.y + 0.5);
    context.lineTo(py.x + 0.5, py.y + 0.5);

    // scale marker
    for (var i = 0; i < length + 2; i++) {
        // xaxis
        context.moveTo(p0.x + (i + 1) * xScaleMarkWidth + 0.5, p0.y + 0.5);
        context.lineTo(p0.x + (i + 1) * xScaleMarkWidth + 0.5, p0.y + 2 + 0.5);

        // yaxis
        context.moveTo(p0.x + 0.5, p0.y - (i + 1) * yScaleMarkWidth + 0.5);
        context.lineTo(p0.x + 0.5 - 2, p0.y - (i + 1) * yScaleMarkWidth + 0.5);
    }

    // y axis marker value
    for (var i = 0; i <= length + 2; i++) {
        // yaxis value
        context.fillText(yAxisValueStep * i, p0.x + 0.5 - 30, p0.y - i * yScaleMarkWidth + 3);
    }

    // draw column chart
    var lengthPerValue = (yScaleMarkWidth * (length + 2)) / max;
    //var rectX, rectY;
    var x, y;
    var i = 0;

    context.font = "normal lighter 12px sans-serif";

    // set axis text & marker
    for (var p in data) {
        x = p0.x + (i + 1) * xScaleMarkWidth + 0.5;
        y = p0.y - lengthPerValue * data[p];

        // add text
        context.fillStyle = ‘rgb(0,0,0)‘;

        // point value
        context.fillText(data[p], x, y - 15);
        // x value
        context.fillText(p, x + xScaleMarkWidth * 0.1, y + lengthPerValue * data[p] + 20);
        i++;
    }

    context.stroke();
    context.closePath();

    context.beginPath();
    context.strokeStyle = "rgba(255,0,0,0.8)";
    context.lineCap = "square";
    context.lineJoin = "miter";
    context.lineWidth = 2;

    i = 0;
    for (var p in data) {
        x = p0.x + (i + 1) * xScaleMarkWidth + 0.5;
        y = p0.y - lengthPerValue * data[p];

        if (i == 0) {
            context.moveTo(x, y);
        }
        else {
            context.lineTo(x, y);
        }
        i++;
    }

    context.stroke();
    context.closePath();
})();