Understanding File Formats

Graphic File Formats

File Formats

• All computer documents, or files, are packaged in different formats.
• Format is determined by the file origin.
• Graphic files can be reduced by using compression formats.

Lossy V.S. Lossless

• Lossy - image data is "lost" or reduced for smaller file size but can cause poor image quality and show "compression artifacts."
• Lossless retains data for higher quality but larger file size and is generally not web friendly.

Graphic Formats

• TIF, JPC, and GIF's are the three most common formats for printing, scanning, and posting on the internet.
• PNG - the common web format and is high quality. It can contain an alpha (transparent) channel.
• TIF - common for desktop publishing, printing, photo, and graphic design. LOSSLESS file format. Retains image data for maximum image quality. Can result in large file sizes (not compatible with internet; print only).
• JPG - created for digital photography and is best for photo content. LOSSY format. Can reduce image file size by 10:1 with no significant compression artifacts. Level of compression is adjustable.
• GIF - Best file format for graphics and images with flat color and tone. Reduces image size by "indexing" color from three channels to one. Adjustible by changing bit levels from one to eight. Contains no Dots Per Inch data. Can contain animation.

Know Your Pixels

• TIF and JPG are best for images that have pixels that blend in color. These pixels are called "contiguous pixels."
• GIF is best for images with even tones
• PNG works for all images, but can result in large file size

• Aliased pixels do not change. 
• The edges will be hard and jagged.
• Anti aliased pixels have smooth edges.
• The pixels will blend.

From High to Low Quality:

The PNG files were the best quality for both the file types, but had the largest file size. High quality JPG's worked well for both, and had a smaller file size.