COS 125
Day 4
Agenda
Assignment 1 Due Assignment 2 Posted
Due Feb 9 @ 9:35 AM 3 missing @ 8:30 AM
Today we will look at creating and using images Examples
http://perleybrook.umfk.maine.edu/samples/imagesplay.htm http://perleybrook.umfk.maine.edu/samples/bk.htm
Factors to Consider for Web Image
Format Color Size/resolution Speed Transparency Animation
Formats
3 Possibilities GIF
Version 87a Older
Version 89a Transparency and animations
Interlaced or non-interlaced JPEG
Compressed (variable) PNG
Optimized or non-optimized palette Interlaced or non-interlaced
Color
Depth (# of colors per pixel) 24 bit
16,777,216 possible colors “true color” Photo quality
16 bit 65,536 colors
8 bit 256 colors
Browser Colors
Most Browser cheat! Lock palette to 256 specific colors
Because of difference in O/S’s only 216 colors are Web Safe http://www.cookwood.com/html/colors/websafecolors.html
Non web safe colors may be dithered or shifted
Check colors in browser before you use them http://perleybrook.umfk.maine.edu/samples/colorchecker.html http://perleybrook.umfk.maine.edu/samples/colorpicker.htm
Size and Resolution
Pixels Monitors are 70-90 pixels per inch Printers are >200 ppi 800 X 600 image
10X7.5 inches on monitor 4X3 inches (or less) on printer
The more pixels on a printer means greater detail The more pixels on a monitor means larger size
Standard SVGA monitors are 800X600 16 bit XGA monitors are 1024X768 24 bit or better
Speed
How fast can the picture be displayed? Factors
Size of graphic file Size of graphic Color depth Compression
Interlacing Sneak peek
How to make graphic load faster Use the right image format
For Photo realistic images use jpeg Lossy compression Use Gaussian blur and re-compress
< 256 colors (logos, text, cartoons) Gif using LZW compression PNG
Only covert images to web format after all editing is done
Transparency
Only for GIF and PNG “remove” one color from image Remove Background (or other color) to make image
non-rectangular and allow web back ground to “bleed” through
Remove color in image to create special effects
Animations
Animated Gifs Flash Both work with frames
Like cartoons Series of images with slight changes between each
image
Where to get images
Buy or download Copyrights
Scan existing images Blake library
Digital camera Blake library
Create using an image editing program Adobe Photoshop and Image ready Macromedia Fireworks JASC Paint Shop Pro
Goggle image search
Inserting a Image Determine after what element in your WebPage you want the
Image to appear Place cursor in your code after the element Type <img src=“image.url”/> “image.url” is location of the file
http://www.server.com/images/image.gif ../images/image.gif images/image.gif image.gif
Hint To place image on a new line use <br/> before <img …/>
Offering Alternative Text
If the image won’t appear, the “alternative text” will <img src=“cat.gif” alt=“Picture of a cat”/> alt is REQUIRED for XHTML Can also use title attribute On some browsers “Alt” text will be a mouse over
pop-up Examples
http://perleybrook.umfk.maine.edu/samples/UsingImages.htm
Specify Size of Image
Tell the Browser how large the picture is to speed up loading
<img src=“image.gif” alt=“a picture” height=“100” width=“100” />
Quick Way Insert image in webpage without dimensions View page and right mouse on image Select properties and determine dimensions Modify img tag with the dimensions
Scaling an Image
Use new values for height and width attributes
CAREFUL –you must maintain aspect ratios or you will distort image Just set height or width and Browser will
automatically set the other
Can also set to percentage of Browser viewable space height =“ 50%” width = “50%”
Thumbnails
A thumbnail is a “mini” version of a larger image <a href=“large.jpg”><image src=“mini.jpg” alt=“A
thumbnail” height = “50” /></a>
Making Images “float”
You can float images in the text You can move image to the left or to the right
relative to text <img src=“image.gif” align=“right”> Use <p></p> after img tag to get text to “fill”
left over space Example
http://perleybrook.umfk.maine.edu/samples/textfloat.htm
Stopping Elements from Wrapping Image
You can control how text & other elements “flows” around your images
<br clear=“left”/> (or right) Next element goes to first available margin on left
<br clear=“all”/> Next element goes to first available spot where both
margins are clear
Adding Space around Image
Create a buffer around your image <img src=“image.gif” alt=“a picture” height=“100”
width=“100” hspace=“20” vspace=“20” />
Aligning images
NOTE: Not all directions work in all browsers Used to align images with text <img src=“image.gif” align=“direction”> Where direction is
TEXTTOP Top of image to top of text
TOP Top of image to top of tallest element
MIDDLE Middle of image with base of text
ABSMIDDLE Middle of image to middle of tallest element
BOTTOM Bottom of image to baseline of text
ABSBOTTOM Bottom of image to bottom of tallest element
Adding Horizontal Rules
A horizontal rule is a line across the Web page <hr/>
size=“10” (how thick) Width=“70%” (how much of the page width) Align=“left” or “right” or “center” noshade=“noshade”
Creating images
Next class we will be using Adobe Photoshop and Image Ready along with JASC’s paint shop pro to create and modify images (including animations)