FILE FORMATS
When you create/use a digital image, it will be saved as a file format. Several are listed below, with their purposes, origins and capabilities. Note: Powerpoint presentations require jpeg images for best results.

MAC VS. WINDOWS FORMATS
PICT: Macintosh standard format.
BMP: Windows standard format. Pronounced "b-m-p." Device-independent bitmap that allows image to display on any device. Comes in two formats: RGB encoded (not compressed, supports 8-bit color) and RLE encoded (lossless compression, 8-bit color) Not to be confused with "bitmap" in reference to a black-and-white image as saved in Photoshop.

COMMONLY USED WEB FORMATS
GIF: (graphic interchange format) Pronounced "jiff." Most common format for web graphics. Ideal for simple graphics. Uses LZW (see below) Interlaced gifs are good for large illustrations while conventional gifs are good for navigation buttons and icons. You can use transparent gifs with caution.
PNG: (portable network graphics): Pronounced "ping." new file format with embedded text, lossless compression, 48-bit color depth, interlacing, automatic gamma correction. Supported by Microsoft Internet Explorer and Netscape Navigator.
JPEG: (joint photographic experts group): 24-bit color images. Most commonly used format for displaying color photographs. Uses lossy compression at high, medium, and low quality. Uses .jpg extension.

COMMONLY USED DESKTOP PUBLISHING FORMATS
EPS: (encapsulated postscript): good for outputting files for printing, especially charts and graphs.
TIFF: (Tagged image file format): widely supported format used commonly in desktop publishing. Can support 24-bit color. Variations of the format, called extensions, sometimes make it difficult to open a file from another source. Can use LSW or other lossless compression.

OTHER FORMATS
PCD: Kodak Photo CD format. Have slides/negatives scanned onto CDs at local photofinisher or service bureau. Results in high quality still superior to most digital cameras.
FPX: Flashpix format. Stored in multiple resolutions for quicker editing and display. Preferred by photographers for highresolution images.
PDD/PSD: Adobe Photo Deluxe and Photoshop formats. Can retrieve layers and changes made within these software programs.
Many scanners/cameras come with their own file format based on their software. Check the program to make sure you can either manipulate the image within the program or export it to another program where you can manipulate it.

COMPRESSION
The reduction in size of a file image. Different file formats use different compression types.
Lossy Compression: as in jpeg images. Image loses quality with compression and doesn't regain it. Medium quality good for images; high quality good for images with text.
Lossless Compression: as in tiff or gif images. Image doesn't lose quality with compression and reopening. See also LZW compression.
LZW Compression: best at compressing images with large fields of homogeneous color. Less efficient for complicated pictures with many colors/textures.Doesn't lose data or distort image. Images with fewer colors will compress more efficiently.

IMAGE/COLOR INFORMATION
Interpolation: interpolated resolution adds pixels to the image using software to determine what color they should be. It is important to note that interpolation doesn't add any new information to the image - it just makes it bigger.
Gamma: degree of contrast between midlevel grays of an image
Resolution: the quality of any digital image depends in part on its resolution and the number of pixels used to create the image. More and smaller pixels add detail and sharpen edges.
- dpi (dots per inch)
- ppi (pixels per inch)
Indexed Color: most common model for the web because files are the smallest. (8 bit)
RGB (red,green,blue): color model used for video displays and recording images via digital camera. Additive color combines the three colors to make white. (24-bit color)
CMYK (cyan,magenta,yellow,black) Color model used for printing. Subtractive colors.
Pixels: short for picture element. Represents a point at an x/y coordinate
Color depth: (expressed in bits) how much memory is assigned to each pixel, based on how much color can be viewed on a monitor. Based on VRAM (Video RAM)
1 bit: black or white (0 or 1)
8bit: each pixel has 8 bits of memory expressed as 1 of 256 colors. Common in older
computers or laptops; referred to as "8 bit" or "256-color" display. However,
"browser safe" color management is based on 8-bit, 216 color.
16 bit: Thousands of colors
24 bit: Can display millions of colors. Referred to as "True color"
Dithering: method of reducing color range of images down to 8-bit or fewer colors. Causes loss of tone and image detail.
Anti-aliasing: Improving the look of screen images by softening jagged pixel edges. See Vector graphics/raster images Vector graphics: (draw or Postscript graphics) illustrations made of lines/shapes. Usually created in a drawing program like Corel Draw or Illustrator.
Raster images: (bitmap or paint images) convert vector graphics to this format for the web. Any illustrations imported into this format automatically are anti-aliased and can be easily resized.