2. Types of Graphics  Vector Individual scalable objects defined by mathematical equations  Bitmap Pixels (tiny, single-colored square) in a grid Most commonly used: ○ GIF ○ JPG ○ PNG

3. GIF (Graphic Interchange Format)  8-bit color information, max. 256 colors  Color info compresses by rows of pixel  good for graphics that contain areas of one color  Lossless compression  Not efficient for photos  Background can be made transparent  Can contain multiple images (animation)

4. JPEG (Joint Photographic Experts Group)  24-bit color information, millions of colors  Lossy compression scheme  Best for photos

5. PNG (Portable Network Graphic)  W3C recommendation and ISO Standard  Can support 8-bit color 16-bit grayscale 24-bit color  Lossless compression scheme  Browser support: www.libpng.org/pub/png/pngapbr.html www.libpng.org/pub/png/pngapbr.html

6. Choosing the Right Format  Goal: Optimize download time ImageUse Graphical, with flat colorsGIF or 8-bit PNG Photo or contains graduated colorJPEG Requires transparencyGIF or PNG Requires animationGIF

7. Color Depth  Truecolor (24- or 32-bit) 24 bits per pixel, 8R 8G 8B “Millions of colors” (16,777,216)  Highcolor (15- or 16-bit) “Thousands of colors” (65,536)

8. Color Depth  Indexed color (8-bit) System contains set of colors (color map) Each color has a number (index) 0-255 Color not available  shifting or dithering Web palette ○ 216 colors shared by MAC and Windows ○ www.learningwebdesign.com/webpalette.html www.learningwebdesign.com/webpalette.html  Statistics: http://www.w3schools.com/browsers/browsers_display.asp

9. Monitor resolution  Live space smaller than monitor size Depends on browser and user setup ResolutionMinimumMaximum 640 x 480623 x 278635 x 580 800 x 600783 x 398795 x 500 1024 x 7681007 x 5661019 x 668

10. Gamma (Monitor Brightness)  Test for different environments PlatformGamma Mac1.8 Windows2.2 Unix2.3 – 2.5

11. Web Graphic Tips  Use web graphics tools (e.g. GIMP)  Keep file sizes small Limit dimensions Reuse and recycle