Getimagedata not working devicePixelRatio is 2, something not compatible must exist somewhere. But it seems to be that getImageData( ) is not working . getImageData: "Uncaught Error: SECURITY_ERR: DOM Exception 18" 6 canvas getImageData doesn't work when running locally on Windows? A community dedicated to all things web development: both front-end and back-end. Half size in width and height, of course considering the window. In your case the function should wait until the image is loaded and draw it onto the canvas right after. The program works fine in Chrome browser. log(), like console. drawImage(). They DO start at the left (and have 8 columns). May 15, 2015 · But getImageData(), putImageData() don't seem to work. Are you sure it's not called? Or is it called but nothing is being logged? Try adding a message to the console. Feb 11, 2024 · When using the getImageData and putImageData methods, it is possible to encounter an overload error. Canvas - can't get image data. height()); The getImageData() method returns an ImageData object that copies the pixel data for the specified rectangle on a canvas. Jul 29, 2011 · I wrote a new version of my script and now, it is working. This error occurs when the arguments passed to the method do not match the expected number or type of arguments. Dec 14, 2012 · Well as per specs the . Aug 3, 2013 · I'm not sure why. If that doesn't work, you probably have to do it the usual way using shaders. I misunderstood the getImageData params. Changing even one pixel and/or recompressing a . log(imageData, "<<<< imageData"). Thanks for contributing an answer to Stack Overflow! Please be sure to answer the question. context. Apr 2, 2013 · colorImage() is a function I've written that changes the pixel values given a corresponding RGB color code, and it definitely does work. Sep 20, 2016 · I am trying to invert the color of an image. T I'm not that experienced with WebGL 2 but it might be possible by not creating a new framebuffer (so content is rendered to the canvas, which is default) and using gl. Jun 26, 2016 · getImageData takes four parameters: https://developer. For example, consider the following code : createCanvas(“1”, 320, 450); setFillColor(“black”); rect(0, 0, 320, 450); … setStrokeColor(rgb(xcurrent * reddelta, greendelta * i, (450 - ycurrent) * bluedelta)); //Plot a Mar 17, 2017 · I suspect your problem here is actually in the use of . Why do they not start at the top? Answer: that's due to divide by 0 on this line when yLoc is 0: xoff = imgWidth Sep 2, 2012 · If so, maybe I can just modify the $. NONE]). When the image. In that object there is an array data which has all your data. src is set, the image still needs to load, so you'll need to use a callback on the load event before ctx. Jun 28, 2014 · Correct, your code will not scale the existing drawings. – Apr 8, 2022 · canvas. Note: The ImageData object is not a picture, it specifies a part (rectangle) on the canvas, and holds information of every pixel inside that rectangle. I would like to be able to manipulate the data many times for example: add/remove various Dec 4, 2012 · Canvas/Photo - getImageData not working. 1. I'm not sure why it wasn't working. I have put up a sample test page showing the problem. The canvas is simply blank. width, img. jpg image by saving it as a new file frequently causes more than one pixel to change due to the rather lossy compression method. You were missing the data , so basically since d is the imagedata element there for it has not element defined for index 3 => d[3] === undefined, Feb 28, 2014 · @srquinn: It is not out of the scope of this question. Description. For example, consider the following code : createCanvas(&hellip; I am loading a picture into a canvas; I drawImage(), store getImageData() into a variable for manipulating. Thank you! saveImage is something very simple: function saveImage(imageName, pixelData) = cacheObject[imageName] = pixelData, where cacheObject is literally just an empry object for starters. Asking for help, clarification, or responding to other answers. mozilla. The above snippet of code does work when I am loading an image locally, but it does not when I try to access an image from an online server, like a public Dropbox account. jpgs for your image files, as these contain artifacts from compression. Oct 21, 2020 · Hooollly shnikies, so simple. Nov 27, 2021 · The culprit is the onload handler inside the drawPicture function. getImageData code to use img2json. putImageData will put the saved original pixels back on the canvas, but putImageData is not a drawing command so its results will not be scaled. You probably want getImageData(0, 0, img. Then I printed out all Canvas/Photo - getImageData not working. getContext("2d"); ccontext. Dec 21, 2012 · Canvas getImageData not working on Mobile Safari. The same code worked well for me in my chrome browser. getImageData(); returns an imagedata object. Canvas Get Image Data returning 0 always. drawBuffers([gl. Here is the new version: $('body'). Provide details and share your research! But avoid …. This method is not affected by the canvas's transformation matrix. May 27, 2019 · I’ve been having problems plotting points using getImageData and setImageData. getImageData(0, 0, $('#canvas'). So in my case using p5js I set the pixel density to be 1 and it worked like a charm; May 27, 2019 · I’ve been having problems plotting points using getImageData and setImageData. The images should start at the top-left of the Canvas. Code: May 26, 2014 · Though all other functions of HTML5 Canvas are working perfectly. canvas getImageData isn't working. Is it common to see appspot applications being down like this? What are the chances of img-to-json coming back up in the recent future? If not, how easy would it be to temporarily download these external images to the server, do the image processing on them, then delete them? Jul 27, 2015 · I'm trying to read image data through the canvas tag and every time I try to retrieve and display that data it all comes up 0's. Modified 12 years, 2 months ago. Specifically, it sometimes works, but for no apparent reason, sometimes it doesn’t. This fixed the issue. For more design-related questions, try /r/web_design. Also, might be due to the image not being loaded. – Aug 15, 2017 · The pixel densities are different on all the devices you mentioned and the ones that have probably 1 dpr (device pixel ratio) are working correctly, whereas the others are not. Ask Question Asked 12 years, 9 months ago. It leaves a black square on the canvas. . So it needed more time to load, I guess - only the accepted answer here says to use an onload function to deal with that, and that's what I had. height). Many people dont have access to the web server (Apache), because they are not the owner (using a hosting provider) and so they can't set the headers, they can't change the servers CORS policy and they certainly cannot restart the server (Quote: "And make sure you restarted Apache"). Hot Network Questions When writing pixels to an HTML Canvas context using putImageData I find that the pixel values are not exactly the same when I fetch them again. 0. If the canvas has images loaded from the hard disk and you try to access pixel information using the getImageData() method, it will not work and will show a security violation "NS_ERROR_DOM_SECURITY_ERR". Viewed 2k times Aug 28, 2015 · I moved the alert() to before the getImageData() call (Thanks, Paul!) and now it works. width(), $('#canvas'). Even if I limit the data grab to 1 pixel it comes up "0, 0, 0, 0". org/en-US/docs/Web/API/CanvasRenderingContext2D/getImageData. canvas getImageData function throws exception in chrome. scale only affects new drawings, not existing drawings. Now the image loads ok, but when I try to call getImageData and putImageData back onto the canvas. 1. drawImage(img, 0, 0); imgData = ccontext. Jul 26, 2024 · The CanvasRenderingContext2D method getImageData() of the Canvas 2D API returns an ImageData object representing the underlying pixel data for a specified portion of the canvas. But won't work using Cocoonjs launcher 2. EDIT: I guess my real question is why the top row of the image is black, and there are only 7 rows, not 8. The getImageData() method returns an ImageData object that copies the pixel data for the specified rectangle on a canvas. Simply marking a function as async using the async prefix isn't enough. prepend(canvas); init_canvas(); ccontext = canvas. srru mry ynmir oyyn ieyl zjjiue gbzfef quby flwbe yjfx oycy gvmw kgyhp vsowqby pplq