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 … Read more
Do not use new Date() This API has several flaws and is only useful for getting the current date + time. Not for measuring timespans. The Date-API uses the operating system’s internal clock, which is constantly updated and synchronized with NTP time servers. This means, that the speed / frequency of this clock is sometimes … Read more
The <canvas> element is within an <iframe>. So to invoke click() on the elements within the <canvas> you have to: Induce WebDriverWait for the desired frame to be available and switch to it. Induce WebDriverWait for the desired element to be clickable. You can use the following solution: Code Block: driver.get(“https://www.online-calculator.com/full-screen-calculator/”) new WebDriverWait(driver, 10).until(ExpectedConditions.frameToBeAvailableAndSwitchToIt(By.id(“fullframe”))); WebElement … Read more
Here’s one technique for zooming at a point: Drawing the map Simplify things by not using transforms to draw the map (no need for translate,scale!). All that’s needed is the scaling version of context.drawImage. What you do is scale the original map to the desired size and then pull it upward and leftward from the … Read more
Wheel of fortune using JS Canvas const sectors = [ {color:”#f82″, label:”Stack”}, {color:”#0bf”, label:”10″}, {color:”#fb0″, label:”200″}, {color:”#0fb”, label:”50″}, {color:”#b0f”, label:”100″}, {color:”#f0b”, label:”5″}, {color:”#bf0″, label:”500″}, ]; // Generate random float in range min-max: const rand = (m, M) => Math.random() * (M – m) + m; const tot = sectors.length; const elSpin = document.querySelector(“#spin”); const ctx … Read more
I’m not sure if there are limitation to canvas dimensions, but data urls have limitations depending on the browser: Data URL size limitations. What you could try is using Node.js + node-canvas (server side) to recreate the canvas. I’ve been using these for creating printable images from canvas elements, and didn’t have any problems/limitations using … Read more
You would want to use instance mode. The first few examples use Global Mode and the next few examples use Instance Mode. Instead of using the default canvas, in instance mode you control where p5js puts the canvas element. If you have two containers, you would use: new p5(leftSketch, ‘left’); new p5(rightSketch, ‘right’); leftSketch and … Read more
From the documentation, these are the parameters for drawImage: drawImage(image, sx, sy, sw, sh, dx, dy, dw, dh); So, to crop the outer 10 pixels from the source image (Assuming it’s 100 * 50), and then to scale that up to 160*60: ctx.drawImage(image, 10, 10, // Start at 10 pixels from the left and the … Read more
The MediaRecorder API is meant to record live-streams, doing edition is not what it was designed to do, and it doesn’t do it very well to be honest… The MediaRecorder itself has no concept of frame-rate, this is normally defined by the MediaStreamTrack. However, the CanvasCaptureStreamTrack doesn’t really make it clear what its frame rate … Read more
Theres a few ways you can do this. You can either add a background to the canvas you are currently working on, which if the canvas isn’t going to be redrawn every loop is fine. Otherwise you can make a second canvas underneath your main canvas and draw the background to it. The final way … Read more