canvas

问题 i am currently building a mobile app and i'm just wondering if it's better (performance wise) to use canvas or img tags. i'll be querying my website for the actual image. just wondering if there is a benefit of one over the other. 回答1: The main benefit is to avoid unnecessary browser decode. For browsers to paint an image onto screen, they would need to: Retrieve the encoded contents of the image file Decode the image from its original JPEG, GIF, PNG or WebP format to a bitmap in memory Paint

问题 i am currently building a mobile app and i'm just wondering if it's better (performance wise) to use canvas or img tags. i'll be querying my website for the actual image. just wondering if there is a benefit of one over the other. 回答1: The main benefit is to avoid unnecessary browser decode. For browsers to paint an image onto screen, they would need to: Retrieve the encoded contents of the image file Decode the image from its original JPEG, GIF, PNG or WebP format to a bitmap in memory Paint

问题 Here is my code in question: $(document).ready(render) function render() { wl = [['hello', 12], ['dear', 10], ['a', 9], ['Joe', 5], ['8', 2]]; $canvas = $('.wordcloud-canvas'); options = { list : wl, fontFamily : 'Times, serif', weightFactor : 2, color : '#f02222', rotateRatio : 0, rotationSteps : 0, shuffle : false, backgroundColor: 'white', drawOutOfBound : false, gridSize : 32 }; window.WordCloud($canvas[0], options); } .wordcloud-view { display: block; margin: 01px 0; width: 100%; height:

问题 Using this JS Fiddle I am able to dynamically create canvases and drag and drop images between all the different canvases. var next = 4 function addCanvas() { // create a new canvas element var newCanvas = document.createElement("canvas"); newCanvas.id = "addedcanvases" + next; //added this to give each new canvas a unique id next++; newCanvas.width = canvasWidth; newCanvas.height = canvasHeight; // add a context for the new canvas to the contexts[] array contexts.push(newCanvas.getContext(

问题 For the purpose of loading images to a canvas, I use this method => const load = (url: string) => new Promise((resolve, reject) => { const image = new Image(); if (!image) reject(); image.crossOrigin = 'Anonymous'; image.src = url; image.addEventListener('load', () => resolve(image)); image.addEventListener('error', err => reject(err)); }); After investigating a lot, I found out that i am encoutring this bug : https://bugs.chromium.org/p/chromium/issues/detail?id=409090 Indeed, randomly

问题 I tried googling for an answer, but I never was able to find a plain answer, or why the answer works. So I would like to know, what is the code that one would use to change the color of an image on canvas? For example, lets say I want to change things to #ff0000 . If a pixel is #000000 , it should stay that way. If a pixel us #ffffff , it should become #ff0000 . Here is my text object constructor: Text = function(x, y, str, s, c){ var img = new Image(); img.src = "font.png"; var alphabet = [

问题 Hi I keep getting an error "Component must be displayable" and cant solve it I looked at the Questions on SO and tried the solutions but to no avail. I'm trying to implement a JVLC player the error occurs when I try " .setVideoOutput(canvas1) " in the Vid class here is the main class. import java.awt.Component; import java.awt.Toolkit; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.awt.event.WindowListener; import java.util.logging.Level; import java.util

问题 I don't understand how swiffy succefully antialias clipping mask when it exports a flash animation that contains mask. Here is my exemple : Full canvas, with mask. Super dirty in Chrome : http://goo.gl/n8yB5h And a swiffy export where there is a picture that move inside a mask. Super clean on Chrome : http://www.creaktif.com/lab/test4.html I tried a lot of things, including draw a 200% canvas then scale it down, adding more points when I draw my mask, but no way to get a clean mask in my

问题 Has anyone here have done clipping an image within an image? I've seen so far about clipping on the canvas but are all regular shapes(rectangle, circle, etc...). It would be nice if some have actually done it. P.S. with fabric.js or just the regular canvas. 回答1: Sure, you can use compositing to draw a second image only where the first image exists: ctx.drawImage(image1,0,0); // this creates the 'mask' ctx.globalCompositeOperation='source-in'; ctx.drawImage(image2,0,0); // this image only

问题 Once again, completely out of my depth but I need to preload some images and then add them to the page when 'all elements (including xml files etc.)' are loaded. The images and references are stored in an array for later access. Trying to draw and image from that array throws an error yet I know it is available as I can just appendTo the page: preloadImages: function (loadList, callback) { var img; var loadedFiles = []; var remaining = loadList.length; $(loadList).each(function(index, address