canvas

问题 I want to create an image object in fabric.js from ImageData object, we can get ImageData from this: var imgData=ctx.getImageData(10,10,50,50); //ctx.putImageData(imgData,10,70); // something liket that var image = new fabric.Image.fromImageData (...); Is there any way to create an image object from ImageData object? 回答1: Let me put my idea here, I don't like this way but have no others around - var ctx = canvas.getContext('2d'); var data = ctx.getImageData(0, 0, 20, 20); var c = document

问题 If both use hardware acceleration (GPU) to execute code, why WebGL is so most faster than Canvas? I mean, I want to know why at low level, the chain from the code to the processor. What happens? Canvas/WebGL comunicates directly with Drivers and then with Video Card? 回答1: Canvas is slower because it's generic and therefore is hard to optimize to the same level that you can optimize WebGL. Let's take a simple example, drawing a solid circle with arc. Canvas actually runs on top of the GPU as

问题 I am writing tests using Jest for components that use canvas elements. I keep getting an error when I run my tests that looks like this. Error: Not implemented: HTMLCanvasElement.prototype.getContext (without installing the canvas npm package) From my understanding Jest uses jsdom for its testing and that jsdom is compatible with canvas if you install the canvas or canvas-prebuilt packages. I have tried installing each of these packages and neither of them have resolved the error. The only

问题 I am writing tests using Jest for components that use canvas elements. I keep getting an error when I run my tests that looks like this. Error: Not implemented: HTMLCanvasElement.prototype.getContext (without installing the canvas npm package) From my understanding Jest uses jsdom for its testing and that jsdom is compatible with canvas if you install the canvas or canvas-prebuilt packages. I have tried installing each of these packages and neither of them have resolved the error. The only

问题 I'm trying to load an image then draw it to a canvas, but I'm only managing to render half of the image presently: var image = new Image(); image.crossOrigin = 'Anonymous'; image.onload = function() { var canvas = document.createElement('canvas'), ctx = canvas.getContext('2d'); ctx.drawImage(image, 0, 0); canvas.style.position = 'absolute'; canvas.style.top = 0; canvas.style.left = 0; document.body.appendChild(canvas); } image.src = 'https://s3.amazonaws.com/duhaime/blog/visualizations/word

问题 I'm trying to load an image then draw it to a canvas, but I'm only managing to render half of the image presently: var image = new Image(); image.crossOrigin = 'Anonymous'; image.onload = function() { var canvas = document.createElement('canvas'), ctx = canvas.getContext('2d'); ctx.drawImage(image, 0, 0); canvas.style.position = 'absolute'; canvas.style.top = 0; canvas.style.left = 0; document.body.appendChild(canvas); } image.src = 'https://s3.amazonaws.com/duhaime/blog/visualizations/word

问题 I'm trying to make a circlular bar progress using html canvas and javascript and i've suceed until I've add a loop with setInterval, since that I'm stuck... I tried to target the problem putting console.log() in all the elements I use to do the loop, but I can't get through why my loop is working in the console but the cirlce doesn't appear. Can anyone help me. I will be very grateful. Thank you in advance. here is my code : class GreyCircle { constructor(x, y, radius) { this.posX = x; this

问题 I have path rect and bitmap, want to add bitmap inside path, While draw on start it appears as expected, but while rotate and draw bitmap goes outside bounds. Here is my code. canvas!!.rotate(rotateAngle.toFloat(), rectF2.centerX(), rectF2.centerY()) canvas!!.drawPath(path, mPaint) bitmap?.let { canvas!!.drawBitmap(it, rectF2.left, rectF2.top, mPaint) } canvas!!.restore() RotateAngle is 0 RotateAngle is 50 回答1: Here is the working solution with matrix. bitmap?.let { val rotate = Matrix()

问题 I have path rect and bitmap, want to add bitmap inside path, While draw on start it appears as expected, but while rotate and draw bitmap goes outside bounds. Here is my code. canvas!!.rotate(rotateAngle.toFloat(), rectF2.centerX(), rectF2.centerY()) canvas!!.drawPath(path, mPaint) bitmap?.let { canvas!!.drawBitmap(it, rectF2.left, rectF2.top, mPaint) } canvas!!.restore() RotateAngle is 0 RotateAngle is 50 回答1: Here is the working solution with matrix. bitmap?.let { val rotate = Matrix()

问题 I have path rect and bitmap, want to add bitmap inside path, While draw on start it appears as expected, but while rotate and draw bitmap goes outside bounds. Here is my code. canvas!!.rotate(rotateAngle.toFloat(), rectF2.centerX(), rectF2.centerY()) canvas!!.drawPath(path, mPaint) bitmap?.let { canvas!!.drawBitmap(it, rectF2.left, rectF2.top, mPaint) } canvas!!.restore() RotateAngle is 0 RotateAngle is 50 回答1: Here is the working solution with matrix. bitmap?.let { val rotate = Matrix()