HTML Images

HTML Images

Example

<!DOCTYPE html>
<html>
<body>

<h2>W3Professors Logo</h2>
<img src="w3professors.png" alt="W3Professors Logo" style="width:304px;height:228px;">

</body>
</html>
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HTML Images Syntax

  • In HTML, images are defined with the <img> tag.
  • The <img> tag is empty, it contains attributes only, and does not have a closing tag.
  • The src attribute specifies the URL (web address) of the image :
  • <img src="url" alt="some_text" style="width:width;height:height;"> 
    

The alt Attribute

The alt attribute provides an alternate text for an image, if the user for some reason cannot view it (because of slow connection, an error in the src attribute, or if the user uses a screen reader).

If a browser cannot find an image, it will display the value of the alt attribute :

Example

<img src="w3professors.gif" alt="W3Professors Logo" style="width:128px;height:128px;"> 
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The alt attribute is required. A web page will not validate correctly without it.

HTML Screen Readers

A screen reader is a software program that reads the HTML code, converts the text, and allows the user to "listen" to the content. Screen readers are useful for people who are blind, visually impaired, or learning disabled.

Image Size - Width and Height

You can use the style attribute to specify the width and height of an image.

The values are specified in pixels (use px after the value) :

Example

<img src="w3professors.gif" alt="w3professors logo" style="width:128px;height:128px;">
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Alternatively, you can use the width and height attributes. Here, the values are specified in pixels by default :

Example

<img src="w3professors.gif" alt="w3professors logo" width="128" height="128">
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Note : Always specify the width and height of an image. If width and height are not specified, the page will flicker while the image loads.

Width and Height, or Style ?

Both the width, height, and style attributes are valid in HTML5.

However, we suggest using the style attribute. It prevents internal or external styles sheets from changing the original size of images :

Example

<!DOCTYPE html>
<html>
<head>
<style>
img {
    width:100%;
}
</style>
</head>
<body>

<img src="W3professors.png" alt="W3Professors Logo" style="width:128px;height:128px;">

<img src="W3professors.png" alt="W3Professors Logo" width="128" height="128">

</body>
</html>
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Images in Another Folder

If not specified, the browser expects to find the image in the same folder as the web page. However, it is common to store images in a sub-folder. You must then include the folder name in the src attribute :

Example

<img src="Images/W3professors.png" alt="W3Professors Logo" style="width:128px;height:128px;">
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Images on Another Server

Some web sites store their images on image servers.

Actually, you can access images from any web address in the world :

Example

<img src="http://www.w3Professors.com/images/w3professors.jpg" alt="W3Professors Logo"> 
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Animated Images

The GIF standard allows animated images :

Example

<img src="w3professors.gif" alt="W3Professors" style="width:450px;height:423px;">
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Note that the syntax of inserting animated images is no different from non-animated images.

Using an Image as a Link

To use an image as a link, simply nest the <img> tag inside the <a> tag :

 <a href="html-images">
  <img src="w3professors.png" alt="W3Professors Logo" style="width:142px;height:142px;border:0;">
</a>   
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Note : border:0; is added to prevent IE9 (and earlier) from displaying a border around the image (when the image is a link).

Image Floating

Use the CSS float property to let the image float to the right or to the left of a text :

 <p><img src="w3professors.png" alt="w3professors logo" style="float:right;width:42px;height:42px;">
The image will float to the right of the text.</p>

<p><img src="w3professors.png" alt="w3professors logo" style="float:left;width:42px;height:42px;">
The image will float to the left of the text.</p>  
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Image Maps

  • Use the <map> tag to define an image-map. An image-map is an image with clickable areas.
  • The name attribute of the <map> tag is associated with the <img>'s use map attribute and creates a relationship between the image and the map.
  • The <map> tag contains a number of <area> tags, that defines the clickable areas in the image-map :
 <img src="planets.gif" alt="Planets" usemap="#planetmap" style="width:145px;height:126px;">

<map name="planetmap">
  <area shape="rect" coords="0,0,82,126" alt="Sun" href="sun.htm">
  <area shape="circle" coords="90,58,3" alt="Mercury" href="mercur.htm">
  <area shape="circle" coords="124,58,8" alt="Venus" href="venus.htm">
</map>

Chapter Summary

  • Use the HTML <img> element to define an image
  • Use the HTML src attribute to define the URL of the image
  • Use the HTML alt attribute to define an alternate text for an image, if it cannot be displayed
  • Use the HTML width and height attributes to define the size of the image
  • Use the CSS width and height properties to define the size of the image (alternatively)
  • Use the CSS float property to let the image float
  • Use the HTML <map> element to define an image-map
  • Use the HTML <area> element to define the clickable areas in the image-map
  • Use the HTML <img>'s element usemap attribute to point to an image-map
Note : Loading images takes time. Large images can slow down your page. Use images carefully.

HTML Image Tags

Tag Description
<img> Defines an image
<map> Defines an image-map
<area> Defines a clickable area inside an image-map