JavaScript canvas2d object method: createLinearGradient()
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The createLinearGradient() method of the JavaScript
DOM object returned
by the getContext("2d")
method applied to the HTML <canvas>
element creates a linear gradient. The resulting object can be used as the
value of the strokeStyle
or fillStyle
properties and hence to fill in rectangles, circles etc. You need to apply some
addColorStop()
methods to the gradient for it to be visible.
It has the following
syntax with the following parameters.
context.createLinearGradient(xstart, ystart,
xend, yend)
Parameter
|
Required / Optional
|
Description
|
xstart
|
Required
|
x-coordinate of
gradient start point
|
xend
|
Required
|
y-coordinate of
gradient start point
|
ystart
|
Required
|
x-coordinate of
gradient end point
|
yend
|
Required
|
y-coordinate of
gradient end point
|
EXAMPLE:
HTML USED IN THIS EXAMPLE:
<!DOCTYPE html>
<html> <!-- Copyright (c) Nematrian Limited 2018 -->
<head></head>
<body>
<span id="element"></span>
<script>
var x2 = document.createElement("CANVAS");
x2.setAttribute("width", "200");
x2.setAttribute("height", "100");
x2.setAttribute("style", "border: 1px solid black");
var c2 = x2.getContext("2d");
var g1 = c2.createLinearGradient(15, 20, 80, 30);
g1.addColorStop(0, "blue");
g1.addColorStop(0.6, "yellow");
g1.addColorStop(0.8, "red");
c2.fillStyle = g1;
c2.fillRect(10, 10, 180, 80);
document.getElementById("element").appendChild(x2);
</script>
</body>
</html>
|
FUNCTION THAT MAY ASSIST IN TESTING WHETHER FEATURE IS SUPPORTED:
function isSupportedJavaScriptMethodCanvas2dCreateLinearGradient() {
var x = document.createElement("CANVAS"); var c = x.getContext("2d"); return !!c.createLinearGradient;
} |
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