html5-canvas

问题 I know very little about OpenGL or WebGL. I was wondering if it is possible to pass a fragment shader an argument. Specifically, I'd like to pass it a multidimensional array with the colors to set for each pixel, for example: [0][0][0] = 1 would be the red component of the pixel at (0, 0). 回答1: The standard way of doing this is by using a texture rather than passing an array. 回答2: Simon's answer is right on . But took me about 6 hours to actually get it working.Here is my full working code as

问题 I found that getImageData of an HTML canvas seems to return incorrect byte values. I generated a 1x1 px image with the following Python code: from PIL import Image import numpy as np a = np.array([[[12, 187, 146, 62]]], dtype=np.uint8) Image.fromarray(a).save('image.png') I converted the image to base64 to include it in this code snippet: let image = document.createElement('img'); image.addEventListener('load', () => { let canvas = document.createElement('canvas'); let ctx = canvas.getContext

问题 I have a HTML Canvas on my website that I use to contain balls that drop into the canvas, they bounce around and have a real good time settling down at the bottom in a range of ways. I was under the impression this was working perfectly. However, it has now been brought to my attention these balls jitter and freak out on other people's computers. I checked the browser they are using and it is the same as mine (Chrome V79). So just to clarify - I have never had it bug on my computer but it

问题 I have a HTML Canvas on my website that I use to contain balls that drop into the canvas, they bounce around and have a real good time settling down at the bottom in a range of ways. I was under the impression this was working perfectly. However, it has now been brought to my attention these balls jitter and freak out on other people's computers. I checked the browser they are using and it is the same as mine (Chrome V79). So just to clarify - I have never had it bug on my computer but it

问题 canvas.onmousemove = function (e) { if (isDown === true) { var pos = getMousePos(canvas, e); var x = pos.x; var y = pos.y; //translate difference from now and start element.translate(x - startX, y - startY); drawImage(); //update start positions for next loop startX = x; startY = y; }} http://jsfiddle.net/braziel/nWyDE/ Friends, I need help to limit the movement of an image within the canvas when zoomed. I put the link, you can see the image when zoomed and dragged it exceeded the limit of

问题 canvas.onmousemove = function (e) { if (isDown === true) { var pos = getMousePos(canvas, e); var x = pos.x; var y = pos.y; //translate difference from now and start element.translate(x - startX, y - startY); drawImage(); //update start positions for next loop startX = x; startY = y; }} http://jsfiddle.net/braziel/nWyDE/ Friends, I need help to limit the movement of an image within the canvas when zoomed. I put the link, you can see the image when zoomed and dragged it exceeded the limit of

问题 I used the following code to save the visible as image. html2canvas(document.querySelector('.specific'), { onrendered: function(canvas) { theCanvas = canvas; Canvas2Image.saveAsPNG(canvas); } }); Is there any way that I can able to save the hidden 回答1: There are some solutions out there, like for example display property toggle, or render inside hidden element. Solution 1 Quickly toggle visibility property const el = document.querySelector('.specific'); el.style.display = "block"; // or any

问题 I am developing application which has whiteboard. Whiteboard should work like idroo.com. One user is drawing something another user should be able to see it on his browser in real time. I use fabricjs as canvas wrapper and it has everithing I need. But I can't emulate free drawing on canvas. I send mouse position and brush options to remote client and try to render them by firing mouse move events. But it don't work. If some body has simialiar problem can you please help? canvasContainer.on(

问题 I have a simple canvas with an image on it (image 500x333): <canvas id="capEdit" width="500" height="333"></canvas> I then apply a simply horizontal flip on the canvas/image using CSS, works perfectly .flipH { -moz-transform: scale(-1, 1); -webkit-transform: scale(-1, 1); -o-transform: scale(-1, 1); transform: scale(-1, 1); filter: FlipH; } I'm now trying to save the image on the canvas WITH its flipped state, but it only saves the original image, here's what I'm trying: $(document).on("click

问题 I have a simple canvas with an image on it (image 500x333): <canvas id="capEdit" width="500" height="333"></canvas> I then apply a simply horizontal flip on the canvas/image using CSS, works perfectly .flipH { -moz-transform: scale(-1, 1); -webkit-transform: scale(-1, 1); -o-transform: scale(-1, 1); transform: scale(-1, 1); filter: FlipH; } I'm now trying to save the image on the canvas WITH its flipped state, but it only saves the original image, here's what I'm trying: $(document).on("click