1. Image Formats

2. What makes one image format different from another?
Differences
What makes one image format different from another?

3. Compression Images can be large files
More disk use
Slower downloads
Compression – ways to cut size of file
Can be Lossy or Lossless

4. Lossy vs. Lossless Lossless Lossy No information is lost
Find other ways to make file smaller
Ex: look for recurring pattern in picture and replace each occurrence with a short abbreviation
Lossy
Accept some degradation of image
Example loss:
Store color info at lower resolution since eye not so sensitive to changes in color

5. Number of Colors
More colors = more memory required to represent each pixel
Different file types accommodate different numbers of colors

6. (Tell them apart based on the file extension – the part after the dot)
File Types
(Tell them apart based on the file extension – the part after the dot)

7. Tagged Image File Format
TIFF
Usually no compression
Very large files
Cannot put directly on website
May come from high quality camera
Tagged Image
File Format

8. RAW Lossless 3-4x smaller than TIFF
Different according to manufacturers of device generating image
Cannot put directly on website

9. Bitmap BMP Uncompressed Proprietary format invented by Microsoft
Cannot put directly on website
Possibly coming from Microsoft Paint
Bitmap

10. Photoshop Document Paint Shop Pro
PSD, PSP
Cannot put directly on website
Photoshop Document
Paint Shop Pro

11. Portable Network Graphic
PNG
Lossless image format
Looks for patterns to compress file size
Compression is exactly reversible (no loss)
Allows transparency and partial transparency
CAN put on website
Portable Network
Graphic

12. Graphics Interchange Format
GIF
Lossy
Creates table of 256 colors
If image has fewer, can render exactly
If more, GIF limits down to 256 colors
If image is true color, GIF may lose % of colors
Allows transparency
Allows animation
CAN put on website
Graphics Interchange
Format

13. Joint Photographic Experts Group
JPG / JPEG
Lossy
Optimized for photos
Very good compression while maintaining high image quality
Degree of compression is adjustable
Use on web for photos
Do not use for line art or images with large areas of a single color with sharp edges
CAN put on website
Joint Photographic
Experts Group