I am currently working on Auto Save module and I have to perform Auto Save process only if any changes made on canvas So, How can I identify the changes?
I have reach two approaches:
By comparing json
For example, when canvas load then I'll store blank canvas json of default atrributes in a variable and if any object/element is added/modified/removed in canvas then I'll update the canvas json and then compare updated canvas json with stored canvas json from variable.
Through fabric.js canvas events
For example, If any event is called of fabric.js
I didn't get any idea that which one is better approach or if there is a better way to detect canvas changes.
Can anyone help me please? It would really be appreciated.
Thanks.
Related
When I load SVGs via fabric.loadSVGFromString(svg), the Fabric Canvas gets stuck and ultimately the browser freezes. However, I don't observe any problems when I use fabric.Image.fromURL(base64Svg). However, I can't utilize base64 converted images since the canvas.toSVG() function returns an image, which I can't use for image conversion. (In my backend, I use an SVG to JPEG converter.)
Is there a way to resolve this problem? Your assistance is much appreciated.
I'm trying to make a DataMatrix reader in javascript that can process an image and extract the information in there. The problem is with detecting the square inside the image with the datamatrix, as this can vary in location and orientation. The input image looks like this:
I want to find and extract only that part (square) of the image that shows the datamatrix, from there on out I have the processing/decoding covered. The desired result for the image above would be:
I need this picture as an ImageData array of some kind, so that I can use that as input for further processing. I am stuck as to how to approach this, how to get the image orientated correctly and the right subsection of the image selected. Is there anyone who has some suggestions/solutions on how to approach this?
Thanks in advance!
I came across this gifx.js - http://evanw.github.io/webgl-filter/ - which seems to work well except for one thing: the save button always generates a blank image. I have tried playing around with the source but do not understand why the data URI that is generated is always the same (and blank) rather than that of the canvas. This is the script that I've been trying to tinker with - http://evanw.github.io/webgl-filter/script.js. If anyone has any ideas, I would appreciate the help!
The WebGL context needs to be created with { preserveDrawingBuffer: true } in the options, otherwise the buffer being rendered is cleared once it is drawn to the screen, and toDataURL will give you a blank image.
See also:
How do you save an image from a Three.js canvas?
I have a little problem to understand the canvas javascript api. What I would like to do is load two png's in memory, so that I have their byte arrays and do some animation with requestAnimationFrame loop.
But I like to load them without displaying them just in memory and access the bytes for some animation effects.
The question is, how would I do something like that. From my observation I learned that I can get the bytes from a canvas via getImageData. But this requires a canvas attached to the DOM and a drawImage call. Is this correct? Is there a way to load the bytes without painting, or drawing anything?
I would then like to use the putImageData method to draw my animated pixel on the screen...? For example line-by-line or some transition effects...
But first...how can I load an prepare my pixel without displaying them?
Any help, links, pointers would be great! If I am on the wrong path please feel free to correct me...
No, the canvas does not need to be in the DOM for manipulations. You can create a canvas just in JavaScript. This is what they usually call a "backing canvas", and usually used for pre-rendering scenes in some libraries.
Here's a demo from HTML5Doctor, where the video is drawn to an off-DOM canvas (It's somewhere at the last part of the article. Search "backing"). It is then "scraped" of it's pixel data for manipulation before it's spit out to the visible canvas.
Just make sure you have the image loaded before painting it into the canvas.
Would anyone be able to tell me if there is a way to apply a color halftone effect to an image using JavaScript and without using WebGL. I need to create it so it can be used across multiple devices and browsers. I have found this but its using WebGL: http://evanw.github.com/webgl-filter/
Would I be able to use three.js or processing.js to achieve it?
Any help would be very appreciated.
Create yourself a canvas element and put the image inside (see link from #Diodeus).
Get the image data from the canvas - now you can iterate over all pixels.
Apply the halftone filter on the image data. see: Algorithm to make halftone images?
Update image data
BTW: I don't recomment to do this on the client machine. Image Processing requires some processing power which may not be available on the client (e.g. Smartphone). Better do it ONCE on the server with e.g. ImageMagick.