Graphic File Formats Notes

  • File Formats
    • All computer documents, or files, are packaged in different formats
    • The format is determined often by the file’s 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 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
  • 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 and 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
  • 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”

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