canvas

Add little lines in fabric js selection controls

由 大兔子大兔子 提交于 2020-02-08 09:50:41
问题 When you have a canvas element set to hasControls little controls render when the user clicks the element. These controls are little canvas squares. I would like to overlay little lines on the square controls to give a further polish to look and feel. 回答1: override fabric Object _drawControl function: fabric.Object.prototype._drawControl = function(control, ctx, methodName, left, top) { if (!this.isControlVisible(control)) { return; } var size = this.cornerSize; this.transparentCorners || ctx

Add little lines in fabric js selection controls

由 我们两清 提交于 2020-02-08 09:50:23
问题 When you have a canvas element set to hasControls little controls render when the user clicks the element. These controls are little canvas squares. I would like to overlay little lines on the square controls to give a further polish to look and feel. 回答1: override fabric Object _drawControl function: fabric.Object.prototype._drawControl = function(control, ctx, methodName, left, top) { if (!this.isControlVisible(control)) { return; } var size = this.cornerSize; this.transparentCorners || ctx

画布跟js.oop

由 ぃ、小莉子 提交于 2020-02-08 09:34:36
<Canvas> 是HTML5中新出现的一个元素。就是可以通过 JS绘制图形。 画布(Canvas)是一个没有内容也没有边框的矩形区域。我们可以控制里面的每一个像素。 下面我们首先定义一个 Canvas元素 ： <canvas id="cancas" width="300" height="300"></canvas> canvas 只有两个属性，width和height，这些属性可选并且可以通过JS或者css来控制： <script type="text/javascript"> function draw() { var c = document.getElementById("cancas"); var cxt = c.getContext("2d");// 它可以通过canvas元素对象的getContext方法来获取，同时得到的还有一些画图需要调用的函数。 getContext() 接受一个用于描述其类型的值作为参数。也就是 后面的 “2d” 或者 “3d” cxt.fillStyle = "#00ff00"; cxt.fillRect(0, 0, 150, 150);//第一个属性时距离x轴的距离，第二个是距离y轴的距离，第三第四个是宽度跟高度 } </script> 在做一个复杂的图形： <script type="text/javascript"> function

What is the best way to remove/delete a function object once instantiated/drawn to canvas?

由 蹲街弑〆低调 提交于 2020-02-07 05:46:25
问题 The snippet code below shows a single function object called "Circle" being drawn to a canvas element. I know how to remove the visual aspect of the circle from the screen. I can simply change its opacity over time with c.globalAlpha=0.0; based on event.listener 's or 'object collision', However if I visually undraw said circle; it still is there and being computed on, its still taking up browser resources as it invisibly bounces to and fro on my canvas element. So my question is: What is the

using images as buttons on html canvas

由 杀马特。学长 韩版系。学妹 提交于 2020-02-07 02:58:31
问题 So I've managed to get javascript code to track the cursor over images displayed on an html canvas thanks to markE, but now I'm trying to treat each one of the images as a button and display a different image when the cursor is hovering. So far, thru many permutations, I have not been able to store an image, or image pathname into an array element that also contains the points we are using to contain the path. Here is the code: <script type="text/javascript" language="JavaScript"> var canvas;

How to display another canvas without zoom in fabricjs

由 孤街浪徒 提交于 2020-02-06 08:01:07
问题 In short, I am developing a project in which there are two canvases: a canvas that supports zoom and drawing, a second canvas - a duplicate of the first canvas, which should display a general view without zoom. Unfortunately, I do not understand how to implement this, since the second canvas also displays a picture with a zoom. Please, help! Here is a small example of what I have: var c1 = document.getElementById("scale"); var c2 = document.getElementById("static"); var canvas = this.__canvas

canvas简单图片处理(灰色处理)

由 …衆ロ難τιáo~ 提交于 2020-02-06 07:15:36
反色处理写的比较简单,灰色处理写了一些注释 <!DOCTYPE html> <html > <head > < meta charset = "UTF-8" > <title ></title > </head > <body > < canvas id ="board" width ="1000" height ="1000" style =" background : lightgrey ;" ></ canvas > </body > </html > < script type ="text/javascript" > var board = document.getElementById( "board"); var context = board.getContext( "2d"); //图像处理必须运行在服务器环境 var aImg = new Image(); aImg.src = "img/7.jpg" ; context.beginPath(); aImg. onload = function (){ //绘制一张图片到 canvas 画布 //三个参数分别为 图片对象 画布位置(X轴 Y轴) context.drawImage(aImg, 10, 10); //getimageData--获取图片指定区域的像素 var imageDatas = context

Chrome toDataUrl quality param is not effect when export jpeg

由 妖精的绣舞 提交于 2020-02-06 05:29:14
问题 Use canvas.toDataURL('image/jpeg', 1) in Chrome, the image is lose a little seriously, but in Firefox, It's ok, almost lossless, even use default quality value 0.92. It seems does not working by setting the quality in Chrome. 回答1: It's a known issue and it's due to how chroma subsampling is handled. Chrome do this differently than Firefox and Safari. The latter ones uses 4:4:4 at 1.0 setting while current Chrome doesn't. However, it seem as the latest Canary (version 33) do the same as the

Chrome toDataUrl quality param is not effect when export jpeg

由 非 Y 不嫁゛ 提交于 2020-02-06 05:28:29
问题 Use canvas.toDataURL('image/jpeg', 1) in Chrome, the image is lose a little seriously, but in Firefox, It's ok, almost lossless, even use default quality value 0.92. It seems does not working by setting the quality in Chrome. 回答1: It's a known issue and it's due to how chroma subsampling is handled. Chrome do this differently than Firefox and Safari. The latter ones uses 4:4:4 at 1.0 setting while current Chrome doesn't. However, it seem as the latest Canary (version 33) do the same as the

Canvas入门03-绘制弧线和圆

由 半城伤御伤魂 提交于 2020-02-06 05:18:39
绘制弧线的API: context.arc(centerx:number, centery: number, radius: number, startAngle: number, endAngle: number, anticlockwise?: boolean) 参数说明： centerX 圆心坐标x centerY 圆心坐标y radius 圆半径 startAngle 起始弧度 endAngle 结束弧度 anticlockwise 是否逆时针绘制，默认false，也就是顺时针绘制 对于一个圆来说，0弧度是从水平方向右侧开始的。 var canvas = document.getElementById('canvas'); canvas.width = 1024; canvas.height = 768; if (canvas.getContext('2d')) { var context = canvas.getContext('2d'); console.log(context); // CanvasRenderingContext2D // context.arc(300, 300, 200, 0, 1.5 * Math.PI); // context.arc(300, 300, 200, 0, 1.5 * Math.PI, true); // context.arc
订阅 canvas