Images

1
Images
2
GIF

• 256 total colors
• Doesn't work well for highly detailed images
• Photographs look grainy
• Indexed color map
• Array where each slot holds an RGB color
• Each pixel of image points to a slot

3
GIF

• Dithering
• Reducing colors in an image by creating patterns
  of available colors that, when viewed together,
  resemble the original color
• Black-and-white checkerboard resembles gray
• Adaptive palette
• Weights colors in the palette based on frequency

4
GIF
5
GIF
6
GIF

• GIF interlacing
• Saves GIF image in several passes
• Pass 1
• Every eighth row starting from the first
• Pass 2
• Every eighth row starting from the fourth
• Pass 3
• Every fourth row starting from the third
• Pass 4
• Remaining rows
• Display is in same order
• Missing lines might be information of initial
  lines
• Blocky effect

7
JPEG

• Can store any number of colors
• Lossy
• Works well for photographic images
• Doesn't work well for line art and images with
  large blocks of color

8
JPEG
9
JPEG
JPEG - 4K Excellent Compression Fair Image Quality
GIF - 26K
JPEG - 12K Good Compression Good Image Quality
JPEG - 21K Fair Compression Excellent Image
Quality
10
JPEG

• Progressive JPEG
• Low to high resolution

11
PNG

• Portable Network Graphics format
• Not patented
• 24-bit color support
• Platform independence
• Capability for interlacing and transparency
• Color maps

12
PNG

• Compression which works equally well for
  photographs and logos
• Header information stored along with image
• Advanced editing capabilities