Computer Images Can store color info about each pixel, but makes file BIG Compression for Web 15

Color Depth Tells number of colors that any pixel can be  black  blue  teal …  white 2 8 = 256 combinations (colors) 8-bit color 00  black 01  dark gray 10  light gray 11  white 2 2 = 4 combinations (colors) 2-bit color 16

Color Depth – it makes a difference! 4-bit color (16)32-bit color (millions)

18 Browser-ready graphics formats GIF (Graphics Interchange Format) –Lossless compression –8-bit color –Good for images with regions of same color

19 Browser-ready graphics formats PNG (Portable Network Graphics) –Lossless compression –24-bit color –Good for text, line-art, and regions with same color –Usually better compression rate than GIF JPEG (Joint Photographic Experts Group) –Lossy compression –24-bit color –Good for photographs 19

20 Defining an Image Map <area href=“____” shape=“_______” coords=“_________” />... same name rect, circle, poly URL or file list of coordinates (what coords you put depends on the shape)

21 Using Coordinates (0,0)(300,0) (300,200) (0,200) (80,50) (80,100) (110,110) (270,180) (200,20) (145,60) (255,60) (200,100)

22 Example centerradius upper left corner lower right corner 1 st coord3 rd coord4 th coord2 nd coord 22