Understanding File Formats Notes

Making the right chose for image compression

- Compression: smaller file size, but worse quality (sound, audio, etc.), throwing out    unneeded data

All documents/files are packaged in different formats

-Often determined by program of origin, a "Native Format", e.g. Photoshop file

- Can be exported as alternate formats, compressing and exporting them as different    file types

Graphic images(pics/video ) have 2 categories of compression, Lossy & Lossless

-Lossy reduces quality but makes much lower quality, Lossless compresses a little W/ little   loss in quality

- JPEG,MPEG,GIF,MP3, are Lossy, TIF& others Lossless

Memory has become very cheap, as compared to earlier tech, becoming smaller & smaller

Lossy images can show "Compression Artifacts" (pixilation and such), something unwanted

Tag Image Format (TIF), JPG, & Graphic Interchange Format (GIF) are the 3 most common formats for displaying pictures, printing, and scanning

PNG is common web format, w/ high quality& can contain alpha channels

- no adjustable levels of compression, but the alpha or transparency channels are useful to    make transparencies for web posting

Each has advantages & disadvantages

TIF

-Tagged Image Format, Lossless

- common format for desktop publishing, print, and graphic design

- NOT internet friendly

JPG/ JPEG

- Joint Photographers Expert Group, Lossy

-Created for digital photography, very common

- can reduce file by a 10:1 ratio w/o significant compression artifacts or loss in image quality

- adjustable compression levels

- no animation or transparency, won't look as good as a TIF when printed out

Other Types of Compression Artifacts

- Flat color in JPGs will be blurred because of contiguous pixels

-Poorly done compression can leave banding in gradients

GIF

-Graphic Interchange Format

-GIF is made for flat artwork, so it is the best format for images w/ flat color

- Reduces image ice by indexing color channels from 3 to 1

- adjustable by changing color bit levels from 1 to 8, 1 color per bit, making photos look awful

-contains no Dots Per Inch (DPI) data for printing, so not a proper format for printing, no resolution

-can have different durations for different frames, allowing for animation

-cinema graphing allowing for minor movements

For Photos

Best quality: TIF or PNG

Smallest size: JPG w/ high quality

max compatibility: Gif

Line art/ Graphics

BQ: PNG or TIF

smallest size TIF, LZW, GIF, or PNG

TIF & JPG for pics w/ contiguous pixels, or blended color

GIF best for flat, even tone or Non-contiguous pixels

Alias vs Anti-Aliase

results in different outlines for curves and diagonals

-Alias has flat, set outlines, diagonal " Jaggies" ( Good for pixel art )

-Anti-Aliasing has a fuzzy blend of pixels near each other