My Notes in Graphic Design 2.17.2015
Notes 2.17.2015
Understanding 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 device such as a digital camera.
* Graphic files such as a photo, video or artwork can be reduced in file size by using image compression formats.
Lossy vs Lossless
* graphic image formats fall under 2 categories of compression, Lossy and Lossless.
* With Lossy, image data is “lost” or reduced for smaller file sizes but can cause poor image quality. Can result in showing “compression artifacts.”
* Lossless retains image data for higher quality, but larger file sizes.
[Don’t use JPEGs for flat graphics unless you like artifacts.]
Graphic Formats
* TIF, JPG and GIF are the 3 most common formats 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.
[TIF is best for high resolution printing.]
File Format: TIF
* Stands for Tagged Image Format.
* Common format for desktop publishing, print, photo and graphic design.
* Is a LOSSLESS file format. It retains image data for maximum image quality.
* Can result in larger file sizes, not fit for display over internet, is not browser compatible.
File Format: 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 by 10:1 without showing significant compression artifacts.
* The level of compression is adjustable.
File Format: GIF
* Stands for Graphics 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 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 proper format for print.
Know Your Pixels
* TIF and JPG are best for images with pixels that blend in color, these are called “contiguous pixels.”
* GIF is best for images with flat even tone, or “non-contiguous pixels.”