Question

I’m trying to fill a portion of a circle with a colour. For example, having a circle with 2/3 red and 1/3 empty.

The Raphael JS documentation doesn’t help much. What is the best way to approach this?

Some examples can be seen at below picture:

var paper = new Raphael(document.getElementById('shape_container'), 400, 100);
var circle = paper.circle(50, 50, 30);
circle.attr (
        {
            fill: '#F00'
        }
    );

With the code above, I can draw a circle with full of red..
I could not find any way for how to fill 2/3 red..

Answer 1

Welcome, Alperen. I believe what you actually want is an arc path rather than a circle. Take a look at this:

function arcpath( canvas, x, y, r, ratio )
{
    if ( ratio >= 1.0 ) return canvas.circle( x, y, r );
    var degrees = 360 * ratio;  //  we use this to determine whether to use the large-sweep-flag or not
    var radians = ( Math.PI * 2 * ratio ) - Math.PI / 2;    //  this is actually the angle of the terminal point on the circle's circumference -- up is Math.PI / 2, so we need to subtract that out.
    var pathparts = 
    [
        "M" + x + "," + y,
        "v" + ( 0 - r ),
        "A" + r + "," + r + " " + degrees + " " + ( degrees >= 180 ? "1" : "0" ) + " 1 " + ( x + ( r * Math.cos( radians ) ) ) + "," + ( y + ( r * Math.sin( radians ) ) ),
        "z"
    ];

    return canvas.path( pathparts );
}

var partial_circle = arcpath( canvas, 250, 350, 100, 0.75 ).attr( { fill: mapit_red, stroke: mapit_black } );

The geometry in the arcpath function is reasonably straightforward (though I had to look up the reference for large-sweep-flag, which was decidedly non-obvious). I’m sure this could be optimized substantially, but it’s a functional first step.