1 Mastering the Internet and HTML Images and Image Tags.

1

Mastering the Internet and Mastering the Internet and HTMLHTML

Images and Image Tags

2

OutlineOutline

Goal Objectives Introduction Image formats Image software Image tags Creating images Editing images Capturing images

Scaling images Image hyperlinks Multiple use of images Image list items GIF Animation Tiling Tutorials FAQs Summary Exercises/Homework

3

GoalGoal

This chapter covers images, their use in Web

pages, their formats, and their tags. It also

covers how to deal with images such as

creation, editing, capture, and scaling

4

ObjectivesObjectives

IntroductionImage formatsImage softwareDealing with images (creation, editing,

capturing, scaling, hyperlinks, multiple use, and list items)

GIF animationTiling

5

IntroductionIntroduction

Images, icons, and logos enhance Web page design

Images are best viewed or downloaded using broadband Internet connections. Larger images take longer to download

Web authors can create images, scan them, or link to them

If used in Web pages, images should be small (thumbnails) and simple

6

Image formatsImage formats Image resolution and format affects its file size.

Higher resolution produces larger size Three image formats are widely supported by the Web.

They are GIF, JPEG (JPG), and PNG The GIF format supports the most commonly used 256

(8-bit) colors; the JPEG format supports the 16.7 million (24-bit) colors

Use the GIF format for simple images created via image programs. Use the JPEG format for complex high-quality images created via scanning real photos, or digital photos

7

Image softwareImage software Images can be created via drawing, scanning, or digital

cameras Image creation and editing include Adobe Photoshop,

Adobe Illustrator, Mapedit, Paint Shop Pro, ThumbsPlus, and WebImage

Image software is 2D. Its coordinate system has an origin in the top left corner of the drawing window (figure 10.1)

Inage viewing software allows viewing large libraries of images. Samples are CompuPic, Lview Pro, ViewSafe, and SnapShot

8

Figure 10.1 Image creation coordinate system

9

Image tagsImage tags

The <IMG> tag, with its attributes, provides Web authors with the control they need to deal with images

The attributes of the <IMG> tag are SRC, ALT, BORDER, WIDTH, HEIGHT, ALIGN, HSPACE, VSPACE, USEMAP, LONGDESC, and ISMAP

10

Creating imagesCreating images

Many image software existsMS Windows Paint program (figure 10.2)

comes installed with Windows OSTo access Paint, click: Start (menu on

bottom left corner of desktop) => Programs => Accessories => Paint

The Paint GUI is simple to use and intuitive (Cont’d)

11

Figure 10.2 MS Windows Paint program

(Cont’d)

12

Creating imagesCreating images Example 10.1 Image in a

Web page (figure 10.3)<HTML><HEAD><TITLE>A Web page with images</TITLE></HEAD><BODY><H2><B><CENTER><FONT COLOR="blue">Web page with a simple

image</FONT></CENTER></B></H2><! Include the image><IMG SRC = "myImage.GIF" ALT = "A GIF image drawn in Paint“BORDER = 5 ALIGN = "middle“HSPACE = 10 VSPACE = 15>Text aligned middle<BR>This text is placed 15 pixels<BR>below the image<BR></BODY></HTML>

13

Editing and capturing imagesEditing and capturing images Image editing may mean changing image content

(cropping it or adding graphics/colors/text), or changing its size (compressing (encoding) or decompressing (decoding) it)

GIF compression maintains the image original colors, while JPEG compression reduces the number of colors

Web authors should not compress and then decompress JPEG images more than once

To capture and save an image off the Web, right click on it and follow prompts

14

Scaling imagesScaling images The WIDTH and HEIGHT attributes of the <IMG> tag are used to scale images Example 10.2 Scaling images (Fig. 10.4)<HTML><HEAD><TITLE>A Web page with scaled

images</TITLE></HEAD><BODY><H2><B><CENTER><FONT

COLOR="blue">Web page with a scaled image</FONT></CENTER></B></H2>

<! Include the image><IMG SRC = "myImage.GIF“ALT = "A GIF image drawn in Paint“BORDER = 5 ALIGN = "middle" HSPACE = 10 VSPACE = 15 WIDTH=100 HEIGHT=125>Text aligned middle<BR>This text is placed 15

pixels<BR>below the image<BR></BODY></HTML>

Figure 10.4 Scaling an image

15

Image hyperlinksImage hyperlinks Images can be used, instead of text, as hyperlinks Example 10.3 Image hyperlinks (Fig. 10.5)<HTML><HEAD><TITLE>A Web page with image hyperlink</TITLE></HEAD><BODY><H2><B><CENTER><FONT COLOR="blue">Web page with an image

hyperlink</FONT></CENTER></B></H2><! Include the image><A HREF = "myIMage.gif"><IMG SRC = "myImage.GIF" ALT = "A GIF image drawn in Paint" ALIGN = "middle" HSPACE = 10 VSPACE = 15 WIDTH = 40 HEIGHT = 50></A>Text aligned middle<BR>This text is placed 15 pixels<BR>below the image<BR></BODY></HTML> (Cont’d)

16

Figure 10.5 Image hyperlink

17

Multiple use of imagesMultiple use of images The same image could be used

more than once in the same Web page

Example 10.4 Multiple use of an image (figure 10.6)(shortened from the top)

<IMG SRC = "myImage.gif"><IMG SRC = "myImage.gif" WIDTH =

100 HEIGHT = 125><A HREF = "myIMage.gif"><IMG SRC = "myImage.GIF" ALT = "A GIF image drawn in Paint" ALIGN = "middle" HSPACE = 10 VSPACE = 15 WIDTH = 40 HEIGHT = 50></A>Text aligned middle<BR>This text is placed 15 pixels<BR> below the image<BR></BODY></HTML>

18

Image list itemsImage list items Images can be used as list items or

item hyperlinks in unordered, ordered, or definition lists

Example 10.5 Image list items (Figure 10.7)

<HTML><HEAD><TITLE>A Web page with image list

items</TITLE></

HEAD><BODY><H2><B><CENTER><FONT COLOR="blue">Web page with image list items</FONT></CENTER></B></H2>

<! Include the image><DL><DT><IMG SRC = "myImage.gif"><DD>This is the original image

<FONT COLOR="red"><DT>Image list item</FONT>

<DD>An image may be used as a list item in unordered, ordered, or definition lists.

<DT><A HREF = "myIMage.gif"><IMG SRC = "myImage.GIF" ALT = "A GIF image drawn in Paint" ALIGN = "middle" HSPACE = 10 VSPACE = 15 WIDTH = 40 HEIGHT = 50></A>

<DD>This is an image hyperlink as a list item.

</DL>

</BODY>

</HTML> (Cont’d)

19

Figure 10.7 Image list items

20

GIF animationGIF animation GIF animation allows a Web author to create a set of image

frames in the desired sequence and save them in one GIF file, as shown below in figure 10.8

Figure 10.8 Animation sequence of a ball

21

TilingTiling When a Web author uses an

image as a page background, the browser repeats it horizontally and vertically in a pattern, thus creating a tiling effect

Example 10.6 Tiling a Web page

<HTML><HEAD><TITLE>A Web page with tiling</TITLE>

</HEAD><BODY BACKGROUND =

"myBox.gif"><H2><B><CENTER><FONT

COLOR="blue">Web page with tiling</FONT></CENTER></B></H2>

<! Include the image><DL><DT><IMG SRC = "myImage.gif"><DD>This is the original image<FONT COLOR="blue"><DT>Image

list item</FONT><DD>An image may be used as a list item

in unordered, ordered, or definition lists.

<DT><A HREF = "myIMage.gif"><IMG SRC = "myImage.GIF" ALT = "A GIF image drawn in Paint" ALIGN = "middle" HSPACE = 10 VSPACE = 15 WIDTH = 40 HEIGHT = 50></A>

<DD>This is an image hyperlink as a list item.

</BODY></HTML> (Figure 10.9)

22

Figure 10.9 Tiling a Web page

23

TutorialsTutorialsTutorial 10.6.1 Right justify an

image (top tags are not shown)<! Include the image><IMG SRC =

"myBox.gif" BORDER = 2 ALIGN = "right">This is an image that is right-justified relative to this text.

<P>It seems that the right and left justifications are more practical than the vertical (top, middle, or bottom) justification.

<P>Yet, a better way of formatting Web pages is to use tables. Yes, HTML uses tables to format Web pages very precisely.

More on tables later. As you can see in this screen capture, the text flows underneath the image as we expect.

</BODY></HTML>

24

FAQsFAQsQ: Why is the browser not displaying the

image in my Web page?– A: The reason is usually unintentional

misuse of the <IMG> tag. Quite often a Web author forgets to close the quotes in the <IMG> tag; for example, <IMG SRC = “xxx.jpg>. Check the <IMG> tag carefully and ensure that its syntax is correct. (Cont’d)

25

FAQsFAQsQ: How can I control the positioning of

text around an image in my Web page?– A: Positioning of text around images in

Web pages cannot be controlled without using tables to format the page, as discussed in chapter 16 of this book. Without tables, Web authors can use the ALIGN attribute which aligns text as shown in figures 10.4 and 10.5.

26

SummarySummary– Images enhance Web page design and presentation– Images are best used with broadband connections– Image variables are resolution and format– Web image formats are GIF, JPEG (JPG), and PNG– Use GIF format for simple images, and JPEG format for

complex images (e.g. photos and scanned pictures)– The HTML image tag is <IMG>. Its attributes are SRC,

ALT, BORDER, WIDTH, HEIGHT, ALIGN, HSPACE, VSPACE, USEMAP, LONGDESC, and ISMAP

– Images can be created, edited, compressed, captured, scaled, animated, and/or used as hyperlinks or list items

27

ExercisesExercises

Problem 10.3. Use two images in a Web page.Use the first image as is, and scale the second one down by 50%. Use the ALT, BORDER, WIDTH, HEIGHT, ALIGN, HSPACE, and VSPACE attributes of the <IMG> tag.– Solution strategy: Follow examples 10.1 and

10.2. Use a text editor to write and debug the HTML code. Use a browser to display the results

(Cont’d)

28

<HTML><HEAD><TITLE>A Web page with scaled images</TITLE></HEAD><BODY><H2><B><CENTER><FONT COLOR="blue">Web page with a scaled

image</FONT></CENTER></B></H2><! Include the first image without scaling><IMG SRC = "problem10.1Image.gif" ALT = "A GIF image without scaling"

BORDER = 5 ALIGN = "middle" HSPACE = 10 VSPACE = 15>Text aligned middle<BR>

This text is placed 15 pixels<BR>below the image<BR><! Include the second image with 50% scaling><IMG SRC = "problem10.2Image.gif" ALT = "A GIF image with 50% scaling"

BORDER = 5 ALIGN = "middle" HSPACE = 10 VSPACE = 15 WIDTH = 200 HEIGHT = 100>Text aligned middle<BR>

This text is placed 15 pixels<BR>below the image<BR></BODY></HTML> (Cont’d)

30

ProblemsProblems

Problem 10.15 Create a Web page that uses an image for a tiling effect. Choose your favorite image for tiling. You could draw it or download it.– Solution strategy: Follow example 10.6. Use a

text editor to write the HTML code. Use a browser to test it

(Cont’d)

31

<HTML><HEAD><TITLE>A Web page with tiling</TITLE></HEAD><BODY BACKGROUND = "tileImage.gif"><H2><B><CENTER><FONT COLOR="blue">Web page with

tiling</FONT></CENTER></B></H2>

<! Include the image><DL><DT><IMG SRC = "myDog2.jpg"><DD>This is the original image<FONT COLOR="blue"><DT>Image list item</FONT><DD>An image may be used as a list item in unordered, ordered, or definition lists.<DT><A HREF = "myDog3.jpg"><IMG SRC = "myDog3.jpg" ALT = "My dog Lucy" ALIGN = "middle" HSPACE = 10 VSPACE = 15 WIDTH = 100 HEIGHT = 70></A><DD>This is an image hyperlink as a list item.

</BODY></HTML> (Cont’d)

1 Mastering the Internet and HTML Images and Image Tags.

Documents

Transcript of 1 Mastering the Internet and HTML Images and Image Tags.