HTML - tutorial - 06 - graphics

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The HTML <canvas> element is used to draw graphics, on the fly, via JavaScript SVG stands for 'scalable vector graphics' and is used to define graphics for the Web. Differences between SVG and canvas


The HTML <canvas> element is used to draw graphics, on the fly, via JavaScript.

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The <canvas> element is only a container for graphics and JavaScript must be used to actually draw the graphics. Canvas has several methods for drawing paths, boxes, circles, text, and adding images.

Canvas examples: a canvas is a rectangular area on an HTML page. By default, a canvas has no border and no content. The markup looks like this: <canvas id="myCanvas" width="200" height="100"></canvas>.
Always specify an "id" attribute (to be referred to in a script), and a "width" and "height" attribute to define the size of the canvas. To add a border, use the "style" attribute.

Add a JavaScript: after creating the rectangular canvas area, you must add a JavaScript to do the drawing.

What can HTML Canvas do?

Canvas can draw colorful text, with or without animation.
Canvas has great features for graphical data presentation with an imagery of graphs and charts.
Canvas objects can move. Everything is possible: from simple bouncing balls to complex animations.
Canvas can respond to JavaScript events.
Canvas can respond to any user action (key clicks, mouse clicks, button clicks, finger movement).
Canvas' methods for animations offer a lot of possibilities for HTML gaming applications.

In conclusion:

The <canvas> element must have an "id" attribute so it can be referred to by JavaScript.
The "width" and "height" attributes are necessary to define the size of the canvas.
Multiple <canvas> elements can be on one HTML page.
By default, the <canvas> element has no border and no content.
To add a border, use a "style" attribute.


SVG stands for 'scalable vector graphics' and is used to define graphics for the Web.

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SVG is a W3C recommendation.

The HTML <svg> element is a container for SVG graphics. It has several methods for drawing paths, boxes, circles, text, and graphic images.

example 1: <svg> element
Sorry, your browser does not support inline SVG.
code:
          <svg class="examples" width="100" height="100">
              <circle cx="50" cy="50" r="40" stroke="green" stroke-width="4" fill="yellow"/>
                Sorry, your browser does not support inline SVG.
          </svg>
        

example 2: <svg> element
Sorry, your browser does not support inline SVG.
code: 
            <svg class="examples" width="400" height="100">
                <rect width="400" height="100" style="fill:rgb(0,0,255);stroke-width:10;stroke:rgb(0,0,0)"/>
                Sorry, your browser does not support inline SVG.
            </svg> 
          

example 3: <svg> element
Sorry, your browser does not support inline SVG.
code:
            <svg class="examples" width="400" height="180">
              <rect x="50" y="20" rx="20" ry="20" width="150" height="150" style="fill:red;stroke:black;
              stroke-width:5;opacity:0.5"/>
              Sorry, your browser does not support inline SVG.
            </svg>
          

example 4: <svg> element
Sorry, your browser does not support inline SVG.
code:
            <svg class="examples" width="300" height="200">
                <polygon points="100,10 40,198 190,78 10,78 160,198" style="fill:lime;stroke:purple;
                stroke-width:5;fill-rule:evenodd;"/>
                Sorry, your browser does not support inline SVG.
            </svg>
          

example 5: <svg> element
SVG Sorry, your browser does not support inline SVG.
code:
            <svg  class="examples" height="130" width="500">
                <defs>
                <linearGradient id="grad1" x1="0%" y1="0%" x2="100%" y2="0%">
                  <stop offset="0%" style="stop-color:rgb(255,255,0);stop-opacity:1"/>
                  <stop offset="100%" style="stop-color:rgb(255,0,0);stop-opacity:1"/>
                </linearGradient>
                </defs>
                <ellipse cx="100" cy="70" rx="85" ry="55" fill="url(#grad1)" />
                <text fill="#ffffff" font-size="45" font-family="Verdana" x="50" y="86">SVG</text>
                Sorry, your browser does not support inline SVG.
            </svg>
          


Differences between SVG and canvas

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SVG is a language for describing 2D graphics in XML. Canvas draws 2D graphics on the fly (with a JavaScript).

SVG is XML based, which means that every element is available within the SVG DOM. You can attach JavaScript event handlers for an element.

In SVG, each drawn shape is remembered as an object. If attributes of an SVG object are changed, the browser can automatically re-render the shape.

Canvas is rendered pixel by pixel. In canvas, once the graphic is drawn, it is forgotten by the browser. If its position should be changed, the entire scene needs to be redrawn, including any objects that might have been covered by the graphic.