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Identifying the Canvas element's methods and properties

From: HTML5: Graphics and Animation with Canvas

Video: Identifying the Canvas element's methods and properties

We've seen how to declaratively create a canvas in HTML. In this example, let's see how we can use script to affect how canvas looks on the browser. So I'm going to open up my example file, and in my exercise files, and I'm in chapter 04, and we'll open up contextprops_start, and you can see we've got some code we need to write. Let's go and take a look at this in the browser really quick. So I'll bring this up in IE, and you can see there's a dotted outline. There is no background color here, just the outline, and what we're going to do is write some code that will affect how the canvas tag itself is displayed in the browser.

Identifying the Canvas element's methods and properties

We've seen how to declaratively create a canvas in HTML. In this example, let's see how we can use script to affect how canvas looks on the browser. So I'm going to open up my example file, and in my exercise files, and I'm in chapter 04, and we'll open up contextprops_start, and you can see we've got some code we need to write. Let's go and take a look at this in the browser really quick. So I'll bring this up in IE, and you can see there's a dotted outline. There is no background color here, just the outline, and what we're going to do is write some code that will affect how the canvas tag itself is displayed in the browser.

So let's go back to the code and over in my snippets, I'm going to copy the three lines under the ContextProps section, so we'll copy those and we'll put them in here, in the window.onload function. So what we're doing here is when the window loads, we've got some code that's going to get a reference to the canvas element by calling getElementById, and that's thus canvas right here. And then we're going to programmatically change the width and height from 400 and 300, which are the defaults, down to 150 x 150. So we save this and then when we go back to the browser. Now when I refresh this, you can see that the canvas got a little bit smaller.

So this shows us how we can programmatically display the canvas using different properties, just the same way that we can do it from HTML. Now in HTML, we can give it attributes that affect how the canvas is displayed initially, but once that height and width is defined in HTML, we can still go back and code and programmatically affect them.

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This video is part of

Image for HTML5: Graphics and Animation with Canvas
HTML5: Graphics and Animation with Canvas

37 video lessons · 18146 viewers

Joe Marini
Author

 
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  1. 4m 54s
    1. Welcome
      1m 3s
    2. Using the exercise files
      2m 3s
    3. Using the HTML5 Canvas element in the real world
      1m 48s
  2. 10m 31s
    1. Real-world example: CanvasMol
      2m 9s
    2. Real-world example: Raphaël-JavaScript Library
      1m 47s
    3. Real-world example: The Wilderness Downtown
      4m 1s
    4. Real-world example: Sketchpad
      1m 10s
    5. Real-world example: Pirates Love Daisies
      1m 24s
  3. 3m 28s
    1. Installing the tools
      1m 29s
    2. Exploring the Canvas examples used in this course
      1m 59s
  4. 8m 58s
    1. Introducing the Canvas tag
      6m 30s
    2. Understanding the differences between Canvas and SVG
      2m 28s
  5. 5m 36s
    1. Identifying the Canvas element's methods and properties
      1m 40s
    2. Using the Canvas drawing context
      3m 56s
  6. 43m 14s
    1. Setting and using colors and styles
      3m 19s
    2. Drawing basic shapes: Rectangles and lines
      10m 21s
    3. Understanding the Canvas state
      5m 15s
    4. Drawing complex shapes: Arcs and paths
      9m 15s
    5. Drawing complex shapes: Bézier and quadratic curves
      5m 46s
    6. Rendering text
      9m 18s
  7. 32m 35s
    1. Creating shadows
      6m 41s
    2. Drawing with patterns
      7m 20s
    3. Drawing with gradients
      6m 18s
    4. Using clipping paths
      4m 46s
    5. Drawing images and video
      7m 30s
  8. 35m 42s
    1. Transforming objects using the translate tag
      4m 18s
    2. Scaling objects with the scale transformation
      4m 7s
    3. Rotating objects with the rotate transformation
      4m 33s
    4. Applying a custom transformation
      6m 58s
    5. Compositing in Canvas using globalAlpha
      6m 36s
    6. Manipulating raw pixels
      9m 10s
  9. 41m 23s
    1. Building an image slideshow control
      4m 24s
    2. Using smooth transitions in a slideshow
      4m 28s
    3. Creating a basic animation
      5m 42s
    4. Creating animation with double buffering
      13m 13s
    5. Incorporating Canvas into a real page
      13m 36s
  10. 48s
    1. Goodbye
      48s

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