canvas – Make Me Engineer

Javascript function to Rotate a base 64 image by X degrees and return new base64

Here is the code <html> <head> </head> <body> <canvas id=”c”/> </body> <script> function rotateBase64Image(base64data, callback) { var canvas = document.getElementById(“c”); var ctx = canvas.getContext(“2d”); var image = new Image(); image.src = base64data; image.onload = function() { ctx.translate(image.width, image.height); ctx.rotate(180 * Math.PI / 180); ctx.drawImage(image, 0, 0); window.eval(“”+callback+”(‘”+canvas.toDataURL()+”‘)”); }; } rotateBase64Image(“data:image/png;base64,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”, ‘callback’); function callback(base64data) { console.log(base64data); … Read more

Drawing a rectangle using click, mouse move, and click

You were close. So, the question isn’t really about the “canvas” element in HTML5, but a canvas that is really a div. http://jsfiddle.net/d9BPz/546/ In order for me to see what your code was trying to accomplish, I had to tidy it up. What needed to happen was tracking of the square element. We are doing … Read more

How to pixelate an image with canvas and javascript

You don’t need to iterate pixel buffer to create a pixelating effect. Simply turn off image smoothing and enlarge a small version of the image to the canvas. This will also mean you can use any image as source (CORS-wise). Example: Fiddle demo // get a block size (see demo for this approach) var size … Read more

Image brightness detection in client side script

This function will convert each color to gray scale and return average of all pixels, so final value will be between 0 (darkest) and 255 (brightest) function getImageLightness(imageSrc,callback) { var img = document.createElement(“img”); img.src = imageSrc; img.style.display = “none”; document.body.appendChild(img); var colorSum = 0; img.onload = function() { // create canvas var canvas = document.createElement(“canvas”); … Read more

Combining two or more Canvas elements with some sort of blending

Of course you can, and you don’t need any funny libraries or anything, just call drawImage with a canvas as the image. Here is an example where I combine two canvas elements onto a third: var can = document.getElementById(‘canvas1’); var ctx = can.getContext(‘2d’); ctx.fillStyle=”rgba(255,0,0,.4)”; ctx.fillRect(20, 20, 20, 80); ctx.fillStyle=”rgba(205,255,23,.4)”; ctx.fillRect(30, 30, 40, 50); ctx.fillStyle=”rgba(5,255,0,.4)”; ctx.fillRect(40, … Read more

Animated GIF in HTML5 canvas

I believe you are looking for http://slbkbs.org/jsgif Unfortunately, the DOM doesn’t expose individual frames of a GIF, so this is done by downloading the GIF (with XMLHttpRequest), parsing it, and drawing it on a <canvas>.

HTML5 Canvas Performance and Optimization Tips, Tricks and Coding Best Practices [closed]

Redraw Regions The best canvas optimization technique for animations is to limit the amount of pixels that get cleared/painted on each frame. The easiest solution to implement is resetting the entire canvas element and drawing everything over again but that is an expensive operation for your browser to process. Reuse as many pixels as possible … Read more

make canvas as wide and as high as parent

Here’s a working example fixing the problems: http://jsfiddle.net/PQS3A/7/ You had several problems with your example: A <div> does not have height or width attributes. You need to set those through CSS. Even if the div were sized correctly, it was using the default position:static, which means that it is NOT the positioning parent of any … Read more

Package cairo was not found in the pkg-config search path. Node j.s install canvas issue

Had the same problem and @Epistemex’s link helped me troubleshoot it. … You need to install libcairo2-dev, libjpeg-dev and libgif-dev packages … sudo apt-get install libcairo2-dev libjpeg-dev libgif-dev

How can I write text on a HTML5 canvas element?

var canvas = document.getElementById(“my-canvas”); var context = canvas.getContext(“2d”); context.fillStyle = “blue”; context.font = “bold 16px Arial”; context.textAlign = ‘center’; context.textBaseline=”middle”; context.fillText(“Zibri”, (canvas.width / 2), (canvas.height / 2)); #my-canvas { background: #FF0; } <canvas id=”my-canvas” width=”200″ height=”120″></canvas>

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