Canvas curved lines - Photoshop

YaBCK
November 6, 2017
190 views
0 votes
2 Answers

I’m using the stroke and path in the canvas to make two lines, which i’m wanting to curve like a wave effect. Instead of creating an actual image in Photoshop to achieve this.

Could anybody help with getting the curves like the example picture below?

I also want to achieve the rounded curve to the straight edge at end, is this possible with stroke path?

What I have so far:

(function($){
  var $canvas,
      fnInitWaves,
      fnDrawWave,
      tmrResize;
  
  fnDrawWave = function(canvas){
    var $this = $(canvas), $outer, iWidth, iHeight, iMidWidth, iQuartWidth, iLineWidth, iFillLineWidth, ctx, ctx1;
      
      $outer = $this.parent();
      
      iWidth = $outer.outerWidth();
      iHeight = $outer.outerHeight() - 30;
      iMidWidth = Math.floor(iWidth / 2);
      iQuartWidth = Math.floor(iMidWidth / 2);
      
      iLineWidth = 10;
      iFillLineWidth = 6;

      $this.attr({width: iWidth, height: 100});
      
      ctx = canvas.getContext('2d');
	  ctx1 = canvas.getContext('2d');
	  
      // Wave init
      ctx.lineWidth = iLineWidth;
      ctx.strokeStyle = '#284762';
      ctx.beginPath();
      ctx.moveTo(0, iHeight * 1);
	 
      // Wave peak
      ctx.quadraticCurveTo(iQuartWidth, -(iHeight / 2.5) + iLineWidth, iMidWidth, iHeight / 2.5);
	  
      // Wave valley
      ctx.quadraticCurveTo(iQuartWidth + iMidWidth, (iHeight * 1.5) - iLineWidth, iWidth, iHeight / 4);
	  
      // Wave end
      ctx.lineCap = 'round';
      ctx.stroke();
      ctx.closePath();
	 	  
	  // Wave init
      ctx1.lineWidth = iLineWidth;
      ctx1.strokeStyle = '#efc833';
      ctx1.beginPath();
      ctx1.moveTo(20, iHeight / 1);
	 	
	  ctx1.quadraticCurveTo(iQuartWidth, -(iHeight / 6) + iLineWidth, iMidWidth, iHeight / 2);
	  ctx1.quadraticCurveTo(iQuartWidth + iMidWidth, (iHeight * 1.5) - iLineWidth, iWidth, iHeight / 1.5);
	  
	  ctx1.lineCap = 'round';
      ctx1.stroke();
      ctx1.closePath();
  };
  
  fnInitWaves = function(){    
    $canvas.each(function(i, el){
      fnDrawWave(el);
    });
  };
  
  $(function(){
    $canvas = $('canvas.wave');
    fnInitWaves.apply(undefined);
  });
  
  $(window).on('resize', function(){
    clearTimeout(tmrResize);
    tmrResize = setTimeout(fnInitWaves, 250);
  });
})(jQuery);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div class="wave-outer">
	<canvas class="wave" width="685" height="96"></canvas>  
</div>

Answers

Chosen as BEST ANSWER

So by taking a look at Developer Nodejs answer. I was able to achieve the result I wanted.

Please take a look at my example:

function Draw(){

canvas = document.getElementById("canvas")
ctx = canvas.getContext('2d');

var $this = $(canvas),$outer, iWidth, iHeight, iMidWidth, iQuartWidth, iLineWidth, iFillLineWidth;
$outer = $this.parent();   
iWidth = $outer.outerWidth();
iHeight = $outer.outerHeight() - 30;
iMidWidth = Math.floor(iWidth / 2);
iQuartWidth = Math.floor(iMidWidth / 2);  
iLineWidth = 10;
iFillLineWidth = 6;

iWidth = $outer.outerWidth();
iHeight = $outer.outerHeight() - 30;
$this.attr({width: iWidth, height: 150});

yellowWave(ctx, iWidth, iHeight, iMidWidth, iQuartWidth);
blueWave(ctx, iWidth, iHeight, iMidWidth, iQuartWidth);

console.log("Curved Lines."); 
  
}

function blueWave(ctx, width, height,
iMidWidth, iQuartWidth){
  var cp1 = iQuartWidth;
  var cp2 = -(height / 1);
  var cp3 = iMidWidth;
  var cp4 = height * 2.5;
  var endX = width;
  var endY = height / 4;
  ctx.lineWidth = 50;
  ctx.strokeStyle = '#284762';
  ctx.beginPath();
  ctx.moveTo(-20, height);
  ctx.bezierCurveTo(
    cp1, 
    cp2,
    cp3,
    cp4, 
    endX, 
    endY
  );


  ctx.lineCap = 'round';
  ctx.stroke();
  ctx.closePath();
}

function yellowWave(ctx, width, height,
iMidWidth, iQuartWidth){
  var cp1 = iQuartWidth;
  var cp2 = -(height / 2.5);
  var cp3 = iMidWidth;
  var cp4 = height * 3.5;
  var endX = width + 50;
  var endY = height / 1.7;
  ctx.lineWidth = 40
  ctx.strokeStyle = '#efc833';
  ctx.beginPath();
  ctx.moveTo(-10, height - 10);
  ctx.bezierCurveTo(
    cp1, 
    cp2,
    cp3,
    cp4, 
    endX, 
    endY
  );


  ctx.lineCap = 'round';
  ctx.stroke();
  ctx.closePath();
}

Draw();

.wave {
  background-color: transparent;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div class="wave-outer">
	<canvas id="canvas" class="wave" width="685" height="96"></canvas>  
</div>

(Edit)

Drawing curves on canvas can be done using bezierCurveTo function:

function draw() {
  var canvas = document.getElementById('canvas');
  if (canvas.getContext) {
    var ctx = canvas.getContext('2d');
    ctx.beginPath();
    ctx.moveTo(25, 100);
    ctx.bezierCurveTo(50, 200, 75, 50, 100, 100);
    ctx.stroke();
  }
}
draw()

Updated answer:

function Draw(){

canvas = document.getElementById("canvas")
ctx = canvas.getContext('2d');

var $this = $(canvas),$outer, iWidth, iHeight, iMidWidth, iQuartWidth, iLineWidth, iFillLineWidth;
$outer = $this.parent();   
iWidth = $outer.outerWidth();
iHeight = $outer.outerHeight() - 30;
iMidWidth = Math.floor(iWidth / 2);
iQuartWidth = Math.floor(iMidWidth / 2);  
iLineWidth = 10;
iFillLineWidth = 6;

iWidth = $outer.outerWidth();
iHeight = $outer.outerHeight() - 30;
$this.attr({width: iWidth, height: 100});

blueWave(ctx, iWidth, iHeight, iMidWidth, iQuartWidth);
yellowWave(ctx, iWidth, iHeight, iMidWidth, iQuartWidth);

console.log("Curved Lines."); 

}

function blueWave(ctx, width, height,
iMidWidth, iQuartWidth){
  var cp1 = iQuartWidth;
  var cp2 = -(height / 2.5);
  var cp3 = iMidWidth;
  var cp4 = height * 2.5;
  var endX = width;
  var endY = height / 4;
  ctx.lineWidth = 16;
  ctx.strokeStyle = '#284762';
  ctx.beginPath();
  ctx.moveTo(0, height);
  ctx.bezierCurveTo(
    cp1, 
    cp2,
    cp3,
    cp4, 
    endX, 
    endY
  );


  ctx.lineCap = 'round';
  ctx.stroke();
  ctx.closePath();
}

function yellowWave(ctx, width, height,
iMidWidth, iQuartWidth){
  var cp1 = iQuartWidth;
  var cp2 = -(height / 2.5);
  var cp3 = iMidWidth;
  var cp4 = height * 2.5;
  var endX = width;
  var endY = height / 3.25;
  ctx.lineWidth = 14;
  ctx.strokeStyle = '#efc833';
  ctx.beginPath();
  ctx.moveTo(6, height + 10);
  ctx.bezierCurveTo(
    cp1, 
    cp2,
    cp3,
    cp4, 
    endX, 
    endY
  );


  ctx.lineCap = 'round';
  ctx.stroke();
  ctx.closePath();
}

Draw();

Original answer: http://jsbin.com/dejatihogo/edit?js

Updated answer: https://jsbin.com/fopesacisa/1/edit?output

The main issue why your lines look crooked or skwed is because you are using the quadratic curves to tie two curved lines together. Instead, use a bezier function so you can bend the one line at two different control points.

Also, no need to duplicate getContext(‘2d’). One is enough.

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Canvas curved lines – Photoshop

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