小编Pum*_*n_M的帖子

在我的控制台我得到的错误:"遗漏的类型错误:不能为空的读取属性'的getContext’"我只是找不到我做了错误......或者我做了什么错.那么也许你可以帮我找到它？请帮忙 :)

enter code here

var canvas = document.getElementById("myCanvas");

var ctx = canvas.getContext("2d");

var cW = canvas.width = 1000; 
var cH = canvas.height = 500; 

var particleAmount = 10; 
var particles = []; 

for(var i=0;i<particleAmount;i++) { 
particles.push(new particle());

}

function particle() { 
this.x = (Math.random() * (cW-(40*2))) + 40; 
this.y = (Math.random() * (cH-(40*2))) + 40; 
this.xv = Math.random()*20-10; 
this.yv = Math.random()*20-10; 

}

function draw () { 
ctx.fillStyle = "black";
ctx.fillRect(0,0,cW,cH);

for(var ii=0;ii<particles.length;ii++){
    var p = particles[ii]; 
    ctx.fillStyle = "red"; …

我想知道是否可以在HTML5中使用彩色画布,然后将其保存为黑白(灰度)PNG,同时单击保存按钮.我设法将画布保存为PNG,这太棒了!但是我想添加灰度功能,而不必使用Illustrator等程序自己更改它.画布有移动粒子顺便说一句.(我不确定这是否有任何影响)

谢谢〜!

function download(){
    var dt = c.toDataURL('image/png');
    this.href = dt; 
}; 
downloadlink.addEventListener('click', download, false); 

我想创建一个通过IBM Bluemix使用twilio的应用程序,但是当我打开我的路线时收到此消息:无法获取/

我认为app.js代码有问题,因为我只是按照一些教程,但它们都不起作用:(

// /*eslint-env node*/

// //------------------------------------------------------------------------------
// // node.js starter application for Bluemix
// //------------------------------------------------------------------------------

// // This application uses express as its web server
// // for more info, see: http://expressjs.com
// var express = require('express');

// // cfenv provides access to your Cloud Foundry environment
// // for more info, see: https://www.npmjs.com/package/cfenv
// var cfenv = require('cfenv');

// // create a new express server
// var app = express();

// // serve the files out of …