Graphic File Formats Understanding Format Choice and Image

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 a 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 catagories 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

Lossy vs Lossless Lossy showing compression artifacts (pixelisation)

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 • Each format has its own advantages, disadvantages

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 a proper format for print

Which format to use?

Know Your Pixels • Tif and JPG are best for images with pixels that vary, these are called “contiguous pixels” • GIF is best for images with flat even tone, or “non-contiguous pixels”

Best format for Print?

Best format for Web?

Best format for Web?