How Can I draw a Text Along arc path with HTML 5 Canvas?

Question

I want to draw a canvas graphic like this flash animation: http://www.cci.com.tr/tr/bizi-taniyin/tarihcemiz/

I drew six arcs and I want to write six words in these

Answer 1

An old old question... nevertheless, on my blog, I take a fairly close look at creating circular text using HTML5 Canvas:

html5graphics.blogspot.com

In the example, options include rounded text alignment (left, center and right) from a given angle, inward and outward facing text, kerning (adjustable gap between characters) and text inside or outside the radius.

There is also a jsfiddle with a working example.

It is as follows:

document.body.appendChild(getCircularText("ROUNDED TEXT LOOKS BEST IN CAPS!", 250, 0, "center", true, true, "Arial", "18pt", 0));

function getCircularText(text, diameter, startAngle, align, textInside, inwardFacing, fName, fSize, kerning) {
    // text:         The text to be displayed in circular fashion
    // diameter:     The diameter of the circle around which the text will
    //               be displayed (inside or outside)
    // startAngle:   In degrees, Where the text will be shown. 0 degrees
    //               if the top of the circle
    // align:        Positions text to left right or center of startAngle
    // textInside:   true to show inside the diameter. False draws outside
    // inwardFacing: true for base of text facing inward. false for outward
    // fName:        name of font family. Make sure it is loaded
    // fSize:        size of font family. Don't forget to include units
    // kearning:     0 for normal gap between letters. positive or
    //               negative number to expand/compact gap in pixels
 //------------------------------------------------------------------------

    // declare and intialize canvas, reference, and useful variables
    align = align.toLowerCase();
    var mainCanvas = document.createElement('canvas');
    var ctxRef = mainCanvas.getContext('2d');
    var clockwise = align == "right" ? 1 : -1; // draw clockwise for aligned right. Else Anticlockwise
    startAngle = startAngle * (Math.PI / 180); // convert to radians

    // calculate height of the font. Many ways to do this
    // you can replace with your own!
    var div = document.createElement("div");
    div.innerHTML = text;
    div.style.position = 'absolute';
    div.style.top = '-10000px';
    div.style.left = '-10000px';
    div.style.fontFamily = fName;
    div.style.fontSize = fSize;
    document.body.appendChild(div);
    var textHeight = div.offsetHeight;
    document.body.removeChild(div);

    // in cases where we are drawing outside diameter,
    // expand diameter to handle it
    if (!textInside) diameter += textHeight * 2;

    mainCanvas.width = diameter;
    mainCanvas.height = diameter;
    // omit next line for transparent background
    mainCanvas.style.backgroundColor = 'lightgray'; 
    ctxRef.font = fSize + ' ' + fName;

    // Reverse letter order for align Left inward, align right outward 
    // and align center inward.
    if (((["left", "center"].indexOf(align) > -1) && inwardFacing) || (align == "right" && !inwardFacing)) text = text.split("").reverse().join(""); 

    // Setup letters and positioning
    ctxRef.translate(diameter / 2, diameter / 2); // Move to center
    startAngle += (Math.PI * !inwardFacing); // Rotate 180 if outward
    ctxRef.textBaseline = 'middle'; // Ensure we draw in exact center
    ctxRef.textAlign = 'center'; // Ensure we draw in exact center

    // rotate 50% of total angle for center alignment
    if (align == "center") {
        for (var j = 0; j < text.length; j++) {
            var charWid = ctxRef.measureText(text[j]).width;
            startAngle += ((charWid + (j == text.length-1 ? 0 : kerning)) / (diameter / 2 - textHeight)) / 2 * -clockwise;
        }
    }

    // Phew... now rotate into final start position
    ctxRef.rotate(startAngle);

    // Now for the fun bit: draw, rotate, and repeat
    for (var j = 0; j < text.length; j++) {
        var charWid = ctxRef.measureText(text[j]).width; // half letter

        ctxRef.rotate((charWid/2) / (diameter / 2 - textHeight) * clockwise);  // rotate half letter

        // draw char at "top" if inward facing or "bottom" if outward
        ctxRef.fillText(text[j], 0, (inwardFacing ? 1 : -1) * (0 - diameter / 2 + textHeight / 2));

        ctxRef.rotate((charWid/2 + kerning) / (diameter / 2 - textHeight) * clockwise); // rotate half letter
    }

    // Return it
    return (mainCanvas);
}