Understanding File Formats

Graphic File Formats

Understanding Format Choice and image compression

Original (raw) files need to be compressed to be able to share-- 

ai psd     ----->>>          jpg png gif 

File Formats

All computer document/files are packaged in different formats

Format is determined by file origin. Ex photoshop, digital camera

Graphic files- (photo/video) artwork can be reduced in size using image compression formats

Lossy vs Lossless 

Graphic image formats fall under 2 categories of compression: Lossy & Lossless

Lossy---

Image data is "lost" or reduced for smaller file sizes, but can cause poor image quality

Lossless---

Retains image data for higher quality, but larger file sizes

 Compression Artifact (pixelisation)

Generational loss---loss of quality over time (copy of copy of copy etc.)

Graphic Formats

TIF  GIF and JPG  -- are (were) the 3 most common formats for common activities --- printing, scanning, displaying images over internet

PNG is common web format. high quality and can contain an alpha (transparency) channel

Each format has its own advantages/disadvantages

File format: TIF

"Tagged Image Format"

common for desktop publishing, print, photo, and graphic design

Lossless file format, retains image data for max image quality'

Can result in larger file sizes- not for display over internet

File Format: JPG

"Joint Photographers Expert Group"

Specifically made for digital photography, best for photo content

Lossy format

Can reduce image size by 10:1 without showing significant compression artifacts

level of compression can be adjustable

File GIF

"Graphic Interchange Format"

Is best for graphic/images that have flat color or even tone- like a cartoon

Reduces image size by "indexing" color from 3 channels to 1

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

Know Your Pixels

TIF/GIF are best for images with pixels that blend in color --- called "contiguous pixels"

GIF is best for images with flat/ even tone "non-contiguous pixels"

Aliase vs Anti-Aliase

Aliased-- jagged edges

Anti-Aliased-- tries to smooth edges