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I've tried this a few different ways, but I keep getting stuck with the same error. I've loaded an image to canvas before, but since I updated Safari a few days ago, I'm getting errors.
I'll post what I have at the moment, but I've tried doing it with jQuery, html's onLoad property, etc.
var cvs, ctx, img; function init() { cvs = document.getElementById("profilecanvas"); ctx = cvs.getContext("2d"); /* Error in getContext("2d") */ img = document.getElementById("profileImg"); drawImg(); } function drawImg() { ctx.drawImage(img, 0, 0); } window.onload = init(); The IDs are correct and correspond to appropriate canvas and img tags. However, I keep getting TypeError: 'null' is not an object (evaluating 'cvs.getContext') and it doesn't seem to be getting any further. I'm sure it's some ID10T error, but I'm hoping someone can give me a clue as to what's causing this? Thank you.
Edit: Okay, so this seems to work using <body onload="init()"> now. However, it only displays occasionally, and if I try to run init() off of $(document).ready() or document.onload I still have no luck, and receive the error. Any thoughts?
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getContext() method returns a drawing context on the canvas, or null if the context identifier is not supported, or the canvas has already been set to a different context mode.
The CanvasRenderingContext2D interface, part of the Canvas API, provides the 2D rendering context for the drawing surface of a <canvas> element. It is used for drawing shapes, text, images, and other objects.
The "Cannot read property 'getContext' of null" error occurs when calling the getContext method on a null value. To solve the error, make sure the JS script tag is loaded after the HTML is declared and the id of the element exists in the DOM.
It is just name for variable. It could be anything. Ctx is just short word for ConTeXt.
For others who hit this page while searching for getContext returning null, it can happen if you have already requested a different type of context.
For example:
var canvas = ...; var ctx2d = canvas.getContext('2d'); var ctx3d = canvas.getContext('webgl'); // will always be null The same is equally true if you reverse the order of calls.
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