Html canvas draw

The Canvas element is a popular HTML 5 tag that can be embedded inside an HTML document for the purpose of drawing and displaying graphics. In this article, we will see how to use the HTML 5 canvas element in an ASP.NET Page to draw shapes and save them to an ASP.NET Image object.Let’s get started. Open Visual Studio 2010/2012 and create a blank ASP.NET Website. Now add a page ‘default.aspx’ to the site. Set it’s target schema for validation as HTML 5 by going to Tools > Options > Text Editor > HTML > Validation. If you do not see the HTML 5 option, make sure you have installed Visual Studio 2010 Service Pack 1and Web Standards Update for Microsoft Visual Studio 2010 SP1.Declare a HTML 5 canvas element of dimensions 400x400, add a Save button and an ASP.NET Image element to the form. We will draw some simple rectangles on this canvas using two functions – fillStyle and fillRectfillRect(float x, float y, float w, float h) – where x & y represent the upper-left corner of the rectangle and w & h represent the width and height of the rectangle you want.fillStyle = “rgba(R, G, B, V)” - we will fill color in this rectangle by using the fillStyle attribute. As you might have guessed, the RGB stand for red, green, and blue values (0–255) of the color you’re creating. ‘V’ represents the visibility factor 0 & 1, where 0 indicates invisibility, and 1 indicates visibility.To draw graphics on a Canvas, you require a JavaScript API that HTML 5 provides. We will be using jQuery to do our client script. Declare the following JavaScript code inside the element of your pagesrc=" $(function () { var canvas = document.getElementById('canasp'); var context = canvas.getContext('2d'); });Note: $(function(){} ensures that code is run only after the Canvas element is fully loaded by the browser. This is better than built-in Javascript event window.onload which has some quirks across browsers (FF/IE6/IE8/Opera) and waits for the entire page, including images to be loaded.We get a reference to the Canvas from the DOM by using getElementById (you can use jQuery code too, but I will stick to the old getElementById for now). We then ask the Canvas to give us a context to draw on. This is done by using the variable context that sets a reference to the 2D context of the canvas, which is used for all drawing purposes. We will now use the fillRect() and fillStyle() function to draw two rectangles. Add this code below the context codecontext.fillStyle = "rgba(156, 170, 193, 1)"; context.fillRect(30, 30, 70, 90); context.fillStyle = "rgba(0, 109, 141, 1)"; context.fillRect(10, 10, 70, 90);The code is pretty simple. We are

This text provides an overview of the HTML5 canvas basic usage. The overview is split into two parts: Declaring an HTML5 canvas element. Drawing graphics on the canvas element.Declaring a Canvas Element First, let's see how to declare a canvas element in an HTML page: HTML5 Canvas not supported The code above declares a single canvas element with width set to 500, height set to 150, and style set to a 1 pixel border with color #cccccc. The text inside the canvas element is ignored, if the browser supports the HTML5 canvas element. If the HTML5 canvas element is not supported, the text will probably be displayed as ordinary text by the browser. You should put the canvas HTML code in your page at the location where you want the canvas to be visible. Just like any other HTML element (e.g. a div element).Drawing Graphics on a Canvas Element Graphics drawn on an HTML5 canvas is drawn in immediate mode. Immediate mode means, that as soon as you have drawn a shape on the canvas, the canvas no longer knows anything about that shape. The shape is visible, but you cannot manipulate that shape individually. It is like a real canvas for a painting. Once painted, all you have left is color pigments / pixels. This is contrary to SVG, where you can manipulate the shapes individually, and have the whole diagram redrawn. In HTML5 you will have to redraw everything yourself, if you want to change the drawn figure. Drawing graphics on an HTML5 canvas element is done using JavaScript, following these steps: Wait for the page to be fully loaded. Obtain a reference to the canvas element. Obtain a 2D context from the canvas element. Draw graphics using the draw functions of 2D context. Here is a simple code example that shows the above steps: // 1. wait for the page to be fully loaded. window.onload = function() { drawExamples(); } function drawExamples(){ // 2. Obtain a reference to the canvas element. var canvas = document.getElementById("ex1"); // 3. Obtain a 2D context from the canvas element. var context = canvas.getContext("2d"); // 4. Draw graphics. context.fillStyle = "#ff0000"; context.fillRect(10,10, 100,100); } First, an event listener function is attached to the window. This event listener function is executed when the page is loaded. This function calls another function I have defined, called drawExamples(). Second, the drawExamples() function obtains a reference to the canvas element using document.getElementById() function, passing the id of the canvas element, as defined in the declaration of the canvas element. Third, the drawExamples() function obtains a reference to a 2D context from the canvas element, by calling canvas.getContext("2d") on the canvas element obtained earlier. Fourth, the drawExamples() function calls various drawing functions on the 2D context object, which results in graphics being drawn on the canvas. Here is how the code looks when executed: HTML5 Canvas not supported

Creating a game like Doodle Jump using HTML, CSS, and JavaScript might seem daunting, but it’s a fantastic way to learn web development. This guide will break down the process of making your own Doodle Jump game with Doodle Jump Code Html, making it accessible even for beginners.Understanding the Core MechanicsBefore diving into the doodle jump code html, let’s understand the core game mechanics. Doodle Jump involves a character constantly jumping upwards, landing on platforms that propel them higher. The goal is to reach the highest possible score before falling off the screen. Obstacles and power-ups can add complexity and excitement.Setting Up Your HTML StructureThe foundation of your game will be a simple HTML file. You’ll need a element to draw the game graphics. Inside the of your HTML, include:This creates a canvas with a specified width and height where your game will reside. Remember to link your JavaScript file in the section. doodle jump html code can help you set up correctly.Bringing Your Game to Life with JavaScriptJavaScript is where the magic happens. You’ll handle game logic, character movement, platform generation, collision detection, and scoring. Here’s a simplified example of how to draw the player:const canvas = document.getElementById('gameCanvas');const ctx = canvas.getContext('2d');const player = { x: 200, y: 500, width: 30, height: 40, draw: function() { ctx.fillStyle = 'green'; ctx.fillRect(this.x, this.y, this.width, this.height); }};player.draw();This code snippet gets the canvas element, creates a 2D rendering context, defines a player object with its properties, and draws a green rectangle representing the player. Adding background music enhances the gaming experience. Check out how to put background music in html code for a guide on implementing audio.Styling Your Game with CSSWhile the core game is built with JavaScript, you can use CSS to style the background and other visual elements. Consider adding background image in html code to create a more visually appealing game.body { background-color: skyblue;}Implementing Game Logic: Movement and Collision DetectionThe core logic of Doodle Jump involves gravity, player movement, and collision detection with platforms. You’ll need to implement functions to handle these aspects. Adding scrolling and platform generation creates an endless

In this article I will explain with an example, how to upload (save) HTML5 Canvas Image to Server in Folder (Directory) in ASP.Net Core MVC. The jQuery Sketch plugin will be used to allow users to draw Signatures and later the HTML5 Canvas Image of the Signature will be uploaded to Server and saved as Image in Folder (Directory). File Location The HTML5 Canvas Image will be saved in the Files Folder (Directory) of wwwroot Folder (Directory). Namespaces You will need to import the following namespaces. using System.IO; using Microsoft.AspNetCore.Hosting; Controller The Controller consists of following Action methods. Action method for handling GET operation Inside this Action method, simply the View is returned. Action method for handling POST operation When Save Button is clicked this Action method gets called which accepts Base64 string returned from the View as a parameter. Then, the Base64 string is converted into a Byte Array. A check is performed whether the Folder (Directory) for saving the HTML5 Canvas Image exists, if not then the Folder (Directory) is created inside the wwwroot using IWebHostEnvironment interface. Finally, the Byte Array is saved as Image file in Folder (Directory) using WriteAllBytes method of File class. public class HomeController : Controller { private IWebHostEnvironment Environment; public HomeController(IWebHostEnvironment _environment) { this.Environment = _environment; } public IActionResult Index() { return View(); } [HttpPost public IActionResult Index(string imageData) { string base64 = imageData.Split(',')[1]; //Convert Base64 string to Byte Array. byte[] bytes = Convert.FromBase64String(base64); string folderPath = Path.Combine(this.Environment.WebRootPath, "Files"); if (!Directory.Exists(folderPath)) { Directory.CreateDirectory(folderPath); } //Save the Byte Array as Image File. System.IO.File.WriteAllBytes(string.Format("{0}\\{1}.png", folderPath, Path.GetRandomFileName()), bytes); return View(); } } View Inside the View, first the ASP.Net TagHelpers is inherited. The View consists of an HTML Form which has been created using the ASP.Net TagHelpers with the following attributes. asp-action – Name of the Action. In this case the name is Index. asp-controller – Name of the Controller. In this case the name is Home. method – It specifies the Form Method i.e. GET or POST. In this case it will be set to POST. The following HTML Form consists of an HTML DIV consisting of two HTML Anchor elements for selecting Marker and Eraser for the HTML5 Canvas Sketchpad and an HTML5 Canvas element. There is also an Input Hidden Field and a Submit Button. The Hidden Field will be used to save the HTML5 Canvas Image as Base64 string. The Submit Button

一、canvas 简介​ 是 HTML5 新增的，一个可以使用脚本(通常为 JavaScript) 在其中绘制图像的 HTML 元素。它可以用来制作照片集或者制作简单(也不是那么简单)的动画，甚至可以进行实时视频处理和渲染。​它最初由苹果内部使用自己 MacOS X WebKit 推出，供应用程序使用像仪表盘的构件和 Safari 浏览器使用。后来，有人通过 Gecko 内核的浏览器 (尤其是 Mozilla和Firefox)，Opera 和 Chrome 和超文本网络应用技术工作组建议为下一代的网络技术使用该元素。​Canvas 是由 HTML 代码配合高度和宽度属性而定义出的可绘制区域。JavaScript 代码可以访问该区域，类似于其他通用的二维 API，通过一套完整的绘图函数来动态生成图形。​ Mozilla 程序从 Gecko 1.8 (Firefox 1.5) 开始支持 , Internet Explorer 从 IE9 开始 。Chrome 和 Opera 9+ 也支持 。二、Canvas基本使用2.1 元素​ 看起来和 标签一样，只是 只有两个可选的属性 width、heigth 属性，而没有 src、alt 属性。​如果不给 设置 widht、height 属性时，则默认 width为300、height 为 150，单位都是 px。也可以使用 css 属性来设置宽高，但是如宽高属性和初始比例不一致，他会出现扭曲。所以，建议永远不要使用 css 属性来设置 的宽高。替换内容​由于某些较老的浏览器（尤其是 IE9 之前的 IE 浏览器）或者浏览器不支持 HTML 元素 ，在这些浏览器上你应该总是能展示替代内容。​支持 的浏览器会只渲染 标签，而忽略其中的替代内容。不支持 的浏览器则 会直接渲染替代内容。用文本替换： 你的浏览器不支持 canvas，请升级你的浏览器。用 替换： 结束标签 不可省略。与 元素不同， 元素需要结束标签()。如果结束标签不存在，则文档的其余部分会被认为是替代内容，将不会显示出来。2.2 渲染上下文(Thre Rending Context)​ 会创建一个固定大小的画布，会公开一个或多个渲染上下文(画笔)，使用渲染上下文来绘制和处理要展示的内容。​ 我们重点研究 2D 渲染上下文。 其他的上下文我们暂不研究，比如， WebGL 使用了基于 OpenGL ES的3D 上下文 ("experimental-webgl") 。var canvas = document.getElementById('tutorial');//获得 2d 上下文对象var ctx = canvas.getContext('2d');2.3 检测支持性var canvas = document.getElementById('tutorial');if (canvas.getContext){ var ctx = canvas.getContext('2d'); // drawing code here} else { // canvas-unsupported code here}2.4 代码模板实例canvas id="tutorial" width="300" height="300">canvas>script type="text/javascript">function draw(){ var canvas = document.getElementById('tutorial'); if(!canvas.getContext) return; var ctx = canvas.getContext("2d"); //开始代码 }draw();script>尝试一下 »2.5 一个简单的例子以下实例绘制两个长方形：实例canvas id="tutorial" width="300" height="300">canvas>script type="text/javascript">function draw(){ var canvas = document.getElementById('tutorial'); if(!canvas.getContext) return; var ctx = canvas.getContext("2d"); ctx.fillStyle = "rgb(200,0,0)"; //绘制矩形 ctx.fillRect (10, 10, 55, 50); ctx.fillStyle = "rgba(0, 0, 200, 0.5)"; ctx.fillRect (30, 30, 55, 50);}draw();script>尝试一下 »三、绘制形状3.1 栅格 (grid) 和坐标空间​如下图所示，canvas 元素默认被网格所覆盖。通常来说网格中的一个单元相当于 canvas 元素中的一像素。栅格的起点为左上角，坐标为 (0,0) 。所有元素的位置都相对于原点来定位。所以图中蓝色方形左上角的坐标为距离左边（X 轴）x 像素，距离上边（Y 轴）y 像素，坐标为 (x,y)。​后面我们会涉及到坐标原点的平移、网格的旋转以及缩放等。3.2 绘制矩形​ 只支持一种原生的图形绘制：矩形。所有其他图形都至少需要生成一种路径 (path)。不过，我们拥有众多路径生成的方法让复杂图形的绘制成为了可能。canvast 提供了三种方法绘制矩形：1、fillRect(x, y, width, height)：绘制一个填充的矩形。2、strokeRect(x, y, width, height)：绘制一个矩形的边框。3、clearRect(x, y, widh, height)：清除指定的矩形区域，然后这块区域会变的完全透明。说明：这 3 个方法具有相同的参数。x, y：指的是矩形的左上角的坐标。(相对于canvas的坐标原点)width, height：指的是绘制的矩形的宽和高。function draw(){ var canvas = document.getElementById('tutorial'); if(!canvas.getContext) return; var ctx = canvas.getContext("2d"); ctx.fillRect(10, 10, 100, 50); ctx.strokeRect(10, 70, 100, 50); }draw();ctx.clearRect(15, 15, 50, 25);四、绘制路径 (path)图形的基本元素是路径。路径是通过不同颜色和宽度的线段或曲线相连形成的不同形状的点的集合。一个路径，甚至一个子路径，都是闭合的。使用路径绘制图形需要一些额外的步骤：创建路径起始点调用绘制方法去绘制出路径把路径封闭一旦路径生成，通过描边或填充路径区域来渲染图形。下面是需要用到的方法：beginPath()新建一条路径，路径一旦创建成功，图形绘制命令被指向到路径上生成路径moveTo(x, y)把画笔移动到指定的坐标(x, y)。相当于设置路径的起始点坐标。closePath()闭合路径之后，图形绘制命令又重新指向到上下文中stroke()通过线条来绘制图形轮廓fill()通过填充路径的内容区域生成实心的图形4.1 绘制线段function draw(){ var canvas = document.getElementById('tutorial'); if (!canvas.getContext) return; var ctx = canvas.getContext("2d"); ctx.beginPath(); ctx.moveTo(50, 50); ctx.lineTo(200, 50); ctx.closePath(); ctx.stroke(); }draw();4.2 绘制三角形边框function draw(){ var canvas = document.getElementById('tutorial'); if (!canvas.getContext) return; var ctx = canvas.getContext("2d"); ctx.beginPath(); ctx.moveTo(50, 50); ctx.lineTo(200, 50); ctx.lineTo(200, 200); ctx.closePath(); ctx.stroke(); }draw();4.3 填充三角形function draw(){ var canvas = document.getElementById('tutorial'); if (!canvas.getContext) return; var ctx = canvas.getContext("2d"); ctx.beginPath(); ctx.moveTo(50, 50); ctx.lineTo(200, 50); ctx.lineTo(200, 200); ctx.fill(); }draw();4.4 绘制圆弧有两个方法可以绘制圆弧：1、arc(x, y, r, startAngle, endAngle, anticlockwise): 以(x, y) 为圆心，以r 为半径，从 startAngle 弧度开始到endAngle弧度结束。anticlosewise 是布尔值，true 表示逆时针，false 表示顺时针(默认是顺时针)。注意：这里的度数都是弧度。0 弧度是指的 x 轴正方向。radians=(Math.PI/180)*degrees //角度转换成弧度2、arcTo(x1, y1, x2, y2, radius): 根据给定的控制点和半径画一段圆弧，最后再以直线连接两个控制点。圆弧案例 1function draw(){ var canvas = document.getElementById('tutorial'); if (!canvas.getContext) return; var ctx = canvas.getContext("2d"); ctx.beginPath(); ctx.arc(50, 50, 40, 0, Math.PI / 2, false); ctx.stroke();}draw();圆弧案例 2function draw(){ var canvas = document.getElementById('tutorial'); if (!canvas.getContext) return; var ctx = canvas.getContext("2d"); ctx.beginPath(); ctx.arc(50, 50, 40, 0, Math.PI / 2, false); ctx.stroke(); ctx.beginPath(); ctx.arc(150, 50, 40, 0, -Math.PI / 2, true); ctx.closePath(); ctx.stroke(); ctx.beginPath(); ctx.arc(50, 150, 40, -Math.PI / 2, Math.PI / 2, false); ctx.fill(); ctx.beginPath(); ctx.arc(150, 150,

IntroductionThis is a proof of concept for building the design canvas for the floorplan editor using Syncfusion React Diagram component. The floorplan editor is a web application that allows users to create and edit floorplans. It provides tools to draw the layout on the html canvas and save the layout to the database. The following sections provide the list of features to be supported in the floorplan editor.FeaturesDesign CanvasThe design canvas is the main area where users can draw the layout of the floorplan. The design canvas provides the following features:Drag and Drop: Users can drag and drop the objects on the design canvas to create the layout.Resize: Users can resize the objects on the design canvas to adjust the size of the layout.Zoom In/Out: Users can zoom in and out the design canvas to view the layout in detail.Freehand Drawing: Users can draw freehand lines on the design canvas to create custom shapes.Grid Snapping: Users can enable grid snapping to align the objects on the design canvas.Rulers: Users can view the rulers on the design canvas to measure the size of the shapes and measure the distance between the shapes.Layers: Users can create multiple layers on the design canvas to organize the layout. The layers can be hidden or shown based on the user's preference.Undo/Redo: Users can undo and redo the actions performed on the design canvas.Boundary Detection: Users can enable boundary detection to prevent the objects from going outside the design canvas.Copy/Paste: Users can copy and paste the objects on the design canvas.View Object Properties: Users can view the properties of the objects on the design canvas. The properties include the name, size, position, and other custom properties.Styling Options: The design canvas should support shapes with different styles like fill color, stroke color, stroke width, line style, line width, and opacity.Text Annotation: Users can add text annotations to the shapes on the design canvas.Image Support: Users can add background images to the design canvas. This could be a floorplan image or any other image that the user wants to use as a reference.Multi-Selection: Users can select multiple objects on the design canvas and perform operations like move, resize, delete, etc.Parent-Child Relationship: Users can create parent-child relationships between the objects on the design canvas. This allows users to group the objects and move them together.Drop Hint: Users can see the drop hint while dragging the objects on the design canvas. The drop hint indicates the position where the element will be dropped.Drag Info: Users can see the drag info while dragging the objects on the design canvas. The drag info provides information about the element being dragged.Highlight Error: There will be some validation rules for the objects on the design canvas. If the user violates the validation rules, the objects should be highlighted with an error color.Object LibraryThe object library is a sidebar that contains a list of objects that users can drag and drop on the design canvas. The element library provides the following features:Tree View: The objects