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javascripthtml5-canvas

Does ctx.stroke() and ctx.fill() automatically close path in canvas?


Is it necessary to include ctx.closePath() if I am going to use ctx.fill() or ctx.stroke() when drawing paths in canvas?
Here is an example below:

ctx.beginPath()
// point 1
ctx.moveTo(x+0.5,y+0.5)
// point2
ctx.lineTo(x2+0.5, y2+0.5)
// point 3
ctx.lineTo(x3+0.5, y3+0.5)

ctx.closePath() // <--- IS THIS NECESSARY ?
ctx.stroke()

Solution

  • The function does what it says, it closes the path, if you want a closed triangle in your example then the closepath() is required, if you want two lines then it's not.

    So the answer to your question is: No, stroke() and fill() does not close your path.

    var c = document.getElementById("myCanvas");
    var ctx = c.getContext("2d");
    
    let x = 10;
    let y = 10;
    
    ctx.beginPath()
    // point 1
    ctx.moveTo(x/2+0.5,y/2+0.5)
    // point2
    ctx.lineTo(x*2+0.5, y*4+0.5)
    // point 3
    ctx.lineTo(x*3+0.5, y*2+0.5)
    
    ctx.closePath() // <--- IS THIS NECESSARY ?
    ctx.stroke()
    
    // New path
    
    x = 50;
    y = 20;
    
    ctx.beginPath()
    // point 1
    ctx.moveTo(x+0.5,y+0.5)
    // point2
    ctx.lineTo(x*2+0.5, y*4+0.5)
    // point 3
    ctx.lineTo(x*3+0.5, y*2+0.5)
    
    ctx.stroke()
    <canvas id="myCanvas" width="200" height="100" style="border:1px solid #d3d3d3;">
    Your browser does not support the HTML canvas tag.</canvas>