<canvas> element has a unique history. But we are not going to focusing on element history. The
<canvas> element takes a bit of work to understand and, unlike your usual run-of-the-mill HTML elements, requires more than just static markup and styling. In this guide, will start with basic understanding of the
canvas element and what kinds of things are required and expected in its associated code. This should help you to get a firm fundamental understanding of
canvas in preparation for creating something interesting and powerful with this unique and other HTML5 elements.
Maybe you heard about HTML 5 Canvas API, but don’t know what it’s good for? It’s the way to go if you want to code an HTML5 game? Or it gives you explicit control over drawing in your browser? So what does all that mean? Just what is the HTML5 Canvas API?
Let me pull back the curtain a little and give you some insight into what the HTML5 Canvas API is all about and what it can do for you and your web apps.
Here are just some of the capabilities at a glance:
- Defining Paths with lines, curves, arcs and more…
- Filling and Stroking Paths
- Clipping to a Path
- Filling and Stroking Text
- Affine Transformation (Translate, Scale, Rotate, Skew)
- Fills using Gradients and Patterns
- Pixel Manipulation
- Offscreen Rendering
- Rendering Blurred Shadows
- Dashed Lines, Line End Caps and Joins
- Exporting Canvas Rendering to a PNG or JPEG
First of all the HTML5 Canvas is a browser DOM object and can be added to your webpage either declaratively through the <canvas> tag or programmatically through the createElement method. Once defined it contains a frame buffer bitmap at screen resolution that is the same width and height of the canvas object itself.
As the element has some complexity so will start with markup.
<canvas id=”canvasId” width=”200″ height=”200″></canvas>
Above tag in your HTML page will create a canvas object on your page, that is 200 pixels width and 200 pixels height and it will be transparent. The DOM object associated with the canvas object doesn’t directly have any drawing methods. In order to actually draw on the canvas, you have to obtain a drawing context object by calling the canvas’s getContext method with a string parameter of “2d”.
//Get reference of canvas object
var canvas = document.getElementById(“canvasId”);
//Get reference of canvas 2d context
var context = canvas.getContext(“2d”);
//Display filled rectangle on screen
context.fillStyle = “rgba(0, 0, 255, .5)”;
context.fillRect(25, 25, 125, 125);
Drawing Rectangles and Paths
//Define path in the shape of triangle with the moveTo and lineTo methods
// Fill the path
You can get in details information about Colors, Styles and Shadows, Line Styles, Rectangles, Paths the drawing API information from the reference.
If the article helpful to you to understand basic idea about HTML5 canvas element than share your thoughts and take a look at the full canvas specification and experiment.
Enjoy RIA… 🙂
There are lots of discussions about Flash and HTML5 and Adobe’s focus on HTML5 and Flash Player on web. But I believe that ‘HTML is the standard and Flash Player is the mechanism which is able to push beyond that standard. There isn’t any competition with between these two technologies‘. I would like to consider the situation like
HTML5 take some tasks from Flash Player and make it cross-platform and across operating systems.
We should target latest new trade and learn new technologies and use best one (from Flash and HTML5) for application situation. So I would like started some fun with HTML5. From this article I would like to start with Adobe Edge Animate series.
Before staring about HTML5 development and Adobe Edge Animate related discussion I would like to list some points for ‘Why we need Adobe Edge Animate when we have a tool like Flash Professional’. There are several reasons like
1. Restrictions of Flash Players with platforms like Apple iOS.
2. HTML technology development
3. Adobe’s shifting focus from Flash Player to HTML
4. Mobile applications usage and developments
5. Learn new technology and tool ( my favorite reason )
Now let’s start with, what we can achieve using Adobe Edge Animate. The tool can be used to create same types of animations and interactions that Flash Player handle on the web in late 1990s, like some basics interaction and movements of visual objects across stage. Edge Animate includes some APIs for enabling interaction through mouse, touch and time based actions. So let’s start with ‘Introduction of Adobe Edge’.
Cascading Style Sheet (CSS), which define how a site or interface structured or designed. Similar as HTML5, CSS3 Specification (which is in draft), can be use for some great effects of objects in Web.
Enjoy RIA.. 🙂
With some recent experience related to application performance, I thought to share some strategies to optimize performance of applications made with Flash Professional. There are two main components that determine Flash performance:
- CPU/GPU usage
- Memory usage
In this article I will begin with discussing memory management guidelines. Several times we are using filters, loops, Timers SoundChannels etc in Flash applications which are playing an important role in application performance.
Easiest techniques for performance optimization:
- Some objects or movie clips required just to represent some data, which doesn’t require user interaction in such cases normally we are not writing any code for that object. But still when user click on such object Flash Player checks for mouse interactions when these objects are present. You can save some CPU cycles by disabling mouse interactivity for objects that do not require mouse interactivity. Disable mouse interactivity.
- The issue with Timers is more critical. If a Timer has not stopped (because its currentCount is less than its repeatCount or because a stop() method has not been applied to it), the Timer will not respond to garbage collection even if you remove its listener and null all references. A Timer’s listener function won’t be called again once you remove the listener, but the Timer still consumes memory. Several times we start timer to achieve function requirement, and even after completion of the functional part execution the timer running. Explicitly stop Timers for garbage collection. However, if you open, play, and then close a Flash game running on a mobile device repeatedly without ever restarting the game, you may see a noticeable problem.
- For ENTER_FRAME event loop, (if required to use then only) use different listeners and different listener functions applied with related DisplayObjects only.
- Avoid use filters. Keep in mind that whenever you apply a filter to a DisplayObject in Flash, its cacheAsBitmap property gets forced to true and Flash must use memory to store that bitmap. If anything changes about that DisplayObject, like its transform operations like size or rotation or a child updates visually, etc, it must regenerate the bitmap, thus using more memory. That old bitmap hangs around until gc kicks in.
- Always use reverse for-loops. Avoid writing do-loops and while-loops.
- Using correct type of display objects for each element
- Use weak event listeners and remove listeners when no longer needed.
- Strictly type variables whenever possible.
- Explicitly disable mouse interactivity when mouse interactivity is not required.
- Replace dispatchEvents with callback functions whenever possible.
- Stop Sounds to enable garbage collection for Sounds and SoundChannels.
- Use the most basic DisplayObject needed for each element.
- Always use cacheAsBitmap and cacheAsBitmapMatrix with air apps (mobile devices).
- Several times when we are playing with loop and require to create object for each iteration in that case. In such situation it would be great if we create one object outside the loop and reuse it repeatedly in loop.
Friends, I hope these would be helpful to optimization of application performance. Feel free to share more ideas and comments about the topic.
Enjoy RIA… 🙂
Like many of today’s developers. I started my IT career as a Flash Developer, and spend much of my time on learning new things from my senior friends, books and blogs about Flash Platform and get idea that there are lots of things to learn like Software Development Life Cycle (SDLC), Software Design Patterns, Coding Standards and many more. With expanding knowledge, I understand that architecture, frameworks and coding standards are important. Before starting discussion about application architecture, would like to share about preface for this post.
There are different technologies are available, we pick one technology, get knowledge for that, practice on that technology’. We live in technologies limitations or boundary and competing with other technologies. It is difficult enough to truly master a single platform. Of course many developers are experts in multiple languages, but mostly their knowledge and development practices of each language are different from each other.
For example, It you want to develop an application in two different languages (let say) Flex and Python. Your knowledge of Flex doesn’t give you any advantage for the Python application development. But I would like to say that knowledge of architecture or framework will help you here for the application development in both the languages. And that’s the reason behind the post on application architecture.
From a set of frameworks, I selected PureMVC as my framework of choice.
Before starting about PureMVC, let’s discuss about what is framework. As I understand Frameworkis a reusable set of libraries or classes for a software system, which follow some rules throughout the application. These rules are known as Design Patterns. So in other words we can say a framework is a collaborating set of design patterns. Frameworks are helpful as it give us the flexibility to implement the fastest solution to given problem.
Currently there are lots of discussions going on between Flash Platform & HTML5 features, development tools, and usage and development standards. But I think there is one topic ‘architecture‘ which is common and useful for all technologies or languages, application architecture/ framework is the heart of application standard, performance and scalability. Technology doesn’t matter for that. So for the reference example, I have selected my favorite platform to explain application architecture. The Adobe Flash Platform is superb for developing rich experiences, including websites, games for web desktop and mobile users. From last few years lightweight, interactive run time has become the ideal choice for expressive media-centric web software. There is a major benefit of Flash Platform can experience as it has expanded to the desktop and well with Adobe AIR.
Goals of PureMVC
PureMVC is lightweight framework based upon well known Model-View-Controller design pattern. Main goals of PureMVC frameworks are:
- To separate application’s coding into three different tiers: model (data), view (UI) and controller (business logic)
- For speedy implementation with scalability and maintainability
- Reduce complexity from developer
Also one major benefit of using well known formal framework is common design patterns and way of adding development. From organizational point of view, usage of such great standard produce clean coding standard of applications and reduce dependency on developers, reduce knowledge transfer time for new developer. I think it’s a best and most attractive benefit of using standard and well known framework. Here are some reasons why I like PureMVC:
- It is easy to learn, great documentation, samples and tutorials, easy to use and also easy to extend.
- It facilitates loosely coupled application architecture (Publish and Subscribe- type), scalability, maintainability and portability for you application.
Developers agree that separating an application’s code into different part based on its functionality. These separations are three major areas: model, view and controller. Let’s have a quick overview of these terms: the model is for your data, the view is for user controls, user interaction, and the controller decides how model change when view is clicked and how view should updates when model updated. You can get basic idea about PureMVC framework from below conceptual diagram:
A forth singleton Façade, simplify development by providing single interface for communication throughout application. Below is the base overview of each singleton:
- Model: manipulating the data model and retrieve data from remote services
- View: mainly refer named mediators that adapt view component.
- Controller: named mapping command classes, which are only created one needed.
- Façade: initializes core singletons (model, view and controller) and provide a single interface for communications.
Will have to use Façade and other actor classes (like Mediator, Proxy/delegate and commands), to interact with singleton as shown below:
Note: In next Part, will update sample applications implemented with PureMVC framework using different programming language.
Adobe Edge Preview 5 introduces some new features and enhancements over previous releases, which play an important role for animation and application optimization. Edge is fully compatible with all modern browsers and can work in mobile browsers. Edge even works in Internet Explorer 9 and this latest version provides a down-level stage for browsers that do not support HTML5, which allows web developers to create animations and post them online without any fear.
Some of the new features in Preview 5 include:
- Optimizing your content for deployment on the web
- Down-level stage for non-HTML5 browsers by using Poster Capture feature
- Preloader tool such as spinning wheels, for indication of animation loading. The loading event also exposed, providing information on the size and giving more control on when it’s used.
- Cursor attributes, so that your cursor changes in appearance when user hovers a link or other actions.
- Timeline based improvements
- Easing functions now available on the timeline control strip, which visualizes how each of them behaves.
- Swap images makes it easier to design with temporary or placeholder images that can be replaced later.
Enjoy RIA… 🙂
Now a days, RIA developers having high expectations from the new tool introduced by Adobe with the named ‘Adobe Edge’, for RIA interactive applications. Some people even say that the new change or trend in HTML5 can compete with great RIA tool like Adobe Flash. As I understand, Flash capabilities are more powerful and more extendable then the current versions of HTML5. At the moment, I don’t see any competition between Flash and HTML5. I think both will have their own place in the market.
Adobe Edge is new promising tool that provides an environment to create HTML5 animations through a timeline (something like flash timeline) and interface using interactive methods and functionalities. It can makes HTML5 animations very easy for designers who do not have experience with coding, and allows them to create HTML5 animation without writing a single line of code.
In this post, I would like to show you how to create a simple HTML5 banner animation using Adobe Edge. Before staring the tutorial, you can download Adobe Edge latest from Adobe Labs.
Assuming that you have some basic idea about animations with Adobe’s other tools.
Let’s start by opening Adobe Edge. Open New File from File menu. Set document width and height properties from Properties panel on left side. Here set Width to 600 px and Height to 200 px. Also you can set title of the document from the Properties panel.
Now from the Properties panel, open the background color picker and set the background color. And set the Overflow to Hidden to hide the objects that are off screen and also you can set Autoplay options.
Choose Import from the File menu and open Edge icon type image and place it in the banner as shown below and set the Edge icon image Width to 180 px and Height to 160 px.
Use Text tool, type “Adobe Edge” and set dimension and font size of the text area.
Now you will animate the Adobe Edge icon and text through the timeline. The timeline in Adobe Edge is similar to other Adobe applications, such as After Effects. When you create an object on the stage you will find that a separate layer is created for it in the timeline. Each layer has sub layer that includes the properties of each layer. In order to create the animation, we will need to create keyframes that represent the change in layers content properties like position. As shown in below screen you can change the translate X and Y position of object.
Now the time line indicator positioned at the beginning of the timeline, move the Adobe Edge icon image to top of the stage and moves the timeline indicator by a few frames and drag the Adobe Edge icon image to its final position in the stage. Apply same thing with text object. Also you will get the animation area of object by different color.
There is an interesting panel known as Elements Panel. It simultaneously servers two purpose. It exposes the document’s DOM and acts as a Library for the items or objects used in your application. The order in which elements appears in this panel is the order in which they appear in the timeline. If you move a timeline layer up or down in the layering order, that change is instantly reflected the Elements panel and vice versa.
Save the file and you can preview it in browser by selecting “Preview in Browser” from File menu.
In this post just show how to create a simple HTML5 animation using Adobe Edge. I think the tool is very simple, it would be helpful for creating animation, especially because in HTML5, it would be more complex to create animation using manual coding.