Graphic File Formats Notes #1

Sep. 16th, 2014 

Graphic File Formats

Understanding Format Choice and Image Compression

 File Formats:

•  All computer documents, or files, are packaged in different formats
• The format is determined often by the files origin, such as a software program like Photoshop, or other devices

Lossy vs Lossless:

• Graphic image formats fall under 2 categories of compression, Lossy and Lossless
• With lossy, the image data is "lost" or reduced for smaller files but can cause poor image quality. Can result in showing "compression artifacts."
• Lossless retains image data for higher quality but larger file sizes.
• Lossy: showing compression artifacts (pixelisation)

Graphic Formats:

• TIF, JPG and GIF are the 3 most common for common activities such as printing, scanning and displaying images over the internet.
• PNG is a common web format, is high quality and can contain an alpha (transparency) channel.
• Each format has its own advantages/disadvantages 

 File Format: TIF

• TIF stands for Tagged Image Format
• Common format for desktop publishing, print, photo and graphic design.

File Format: JPG

• JPG stands for Joint Photographers Expert Group
• Created for digital photography and works best for photo content.
• Is a LOSSY format.
• Can reduce an image file size bye 10:1 without showing significant compression artifacts.
• The level of compression is adjustable.

File Format: GIF

• Stands for Graphic Interchange Format
• Is best for graphics or images that have flat color or even tone, such as a cartoon.
• Reduces image size by "indexing" color bit levels from 1 to 8
• Is adjustable by changing color bit levels from 1 to 8
• Contains no DPI (Dots per inch) data for printing. Not a proper format for print.