Globale linker
Book 1
- Chapter 1
- Chapter 2
- Chapter 3
- Chapter 4
- Chapter 5
- Chapter 6
- Chapter 7
- Chapter 8
- Chapter 9
- Chapter 10
- Chapter 11
- Chapter 12
- Chapter 13
- Chapter 14
- Chapter 15
- Chapter 16/17
- Chapter 18/19
- Chapter 20
- Chapter 21
- Chapter 22/23
Book 2
Ch.5 Web Graphics
Users have come to expect a visually pleasing experience that can only be achieved with the use of images. Images can also be used for navigation in the form of image maps and graphical buttons that link to other pages or resources. Good web graphics must be aestethically pleasing, functional and small in file size.
Color depth: this information, measured in bits, determine how many colors each pixel can display. As color depth increases, so does the file size.
To keep file sizes as small as possible:
- Use colors from the web-safe color palette
- Use the least numbers of colors possible
- Use solid color whenever possible
- Avoid anti-aliasing when possible
- Use optimization utilities such as Photoshop, Fireworks and ImageReady
- Slice images and reconstruct using tables in HTML
Image resolution: higher screen resolution display sharper, clearer images, because the pixels are forced closer together. Standard screen resolution is 640x480, or 72 dpi (dots per inch).
Palettes: a slight difference exists between Microsoft Windows system palette and the Netscape Navigator browser palette. Navigator use a 216 color palette, Windows use a 256 color palette.
Dithering: The approximation or reconciliation of colors between the image palette and the system palette. Colors in the image are replaced to match the colors the system palette.
Bitmap: are composed of individual values for each color to be displayed. The larger the dimension, the larger the file size.
- Paint programs:
- Adobe Photoshop
- Jasc Paint Shop Pro
- Corel Photo-Paint
- Macromedia Fireworks
Vector: store information about the image in mathematical instructions that are interpreted and displayed. Is not resolution-depentent.
- Vector programs:
- Adobe Illustrator
- Macromedia Flash
- Corel Draw
- Macromedia Freehand
Image file formats include:
- GIF
256 colors, can be transparent, and can be «animated». Best for drawings, logos and flags. Supported in all browsers. - JPG (JPEG)
16,7 mill. colors. Best for photographs, gradients and shadows. Supported in all browsers. - PNG
Not widely supported in browsers. Plug-in needed. - TIFF
Not supported in browsers. For print. - BMP
Not supported in other than IE. Plug-in needed. - SVG
Based on XML. Not supported by browsers. Plug-in needed. - SWF
Flash-animation. Plug-in needed.
The ALT attribute provides alternative text in place of images on an HTML page. Is placed in the IMG-tag
<img src="image.gif" width="10" height="10" alt="alternative text">
