-Graphic file formats
-Compression
-Choice and image
Understanding Format
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 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 under 2 categories of compression, Lossy and Lossless
With lossy, images data is "lost" or reduced for smaller files but can cause poor images quality.
Can result in showing "compression artifacts"
Lossless retains image data for higher quality, but larger file size.
Graphic Formats
TIF, JPG and GIF are the 3 most common formats for common activities 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 its own advantages, disadvantages
TIF
Stands for Tagged Image Format
Common format for desktop publishing, print, photo and graphic design.
Is a LOSSLESS file format. It retains images data for maximum image quality.
Can result in larger file size, not fit for display over internet, is not browser compatible.
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
GIF
Stands for Graphic Interchanges Format.
Is best for graphics or images that have flat color or even tone, such as cartoon.
Reduces image size by "indexing" color from 3 channels to 1.
Is adjustable by changing color bit level from 1 to 8.
Contains no DPI (Dots Per Inch) data for printing. Not a proper format for print.
Photographic images:
Photos are continuous tones, 24 bit color or 8 bit Gray, no text, few lines and edges, (proprieties).
TIF or PNG (lossless compression and no JPG artifacts)(For unquestionable best quality)
JPG with higher quality factor can be decent. (Smallest file size)
TIF or JPG for maximum compatibility.
256 color Gif is very limited color, and is a larger file than 24 bit JPG (Worst choice)
Graphics, including logos or line art
Graphics are often solid colors, up to 256 colors, with text or lines and sharp edges. ( For unquestionable quality)
Worst choice for graphics and such are GIFs
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 flat tone, or "Non-contiguous pixels".
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