Plotting & Viewing Tools
- gnuplot
- xv
Sampling & Quantization Review
Re-Quantization Example
Re-Sampling Example
| 16 gray levels | 4 gray levels |
|---|---|
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Note: the above images are greatly enlarged. A 5 x 5 pixel image wouldn't be visible on the web page.
| 6 x 6 | 3 x 3 |
|---|---|
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Same sized pixels after resampling.
CAT 256 X 256
CAT 128 X 128
CAT 64 X 64
CAT 32 X 32
CAT Reenlarged
CAT 256 gray levels
CAT 128 gray levels
CAT 64 gray levels
CAT 32 gray levels
CAT 16 gray levels
CAT 8 gray levels
CAT 4 gray levels
CAT 2 gray levels
Other Quantization Examples
- cat image,
- continuous,
- sampled,
- Low Freq. image, high sample rate,
- Low Freq. image, medium sample rate,
- Low Freq. image, low sample rate,
- Low Freq. image, really low sample rate,
- High Freq. image, high sample rate,
- High Freq. image, medium sample rate,
- High Freq. image, low sample rate, and
- High Freq. image, really low sample rate.
- Cat image: 512 x 512, 256 x 256, 128 x 128, 64 x 64, 32 x 32, and 16 x 16 spatial quantization.
Pixel Relationships
- Neighbors
- 4-neighbors N4(p) (left, right, top, bottom)
- 4 diagonal neighbors ND(p) (upper left, upper right, lower left, lower right)
- 8-neighbors N8(p) = N4(p) + ND(p)
- Border pixels are special cases.
- connectivity, N4, N8, ND, M-connectivity, NM, sample0, sample1, and sample2.
- Based on a set of gray levels called V(G). If V(G)={3,4,5}, then only pixels with these gray levels are considered for adjacency.
- 4-adjacency: p and q with values from V are 4-adjacent if q is in the set N4(p).
- 8-adjacency: p and q with values from V are 8-adjacent if q is in the set N8(p).
- m-adjacency: p and q with values from V are m-adjacent if q is in N4(p) or q is in ND(p) AND the set N4(p) intersect N4(q) has no pixels from V. (See Fig2.26)
- A path exists from p to q if you can find
a sequence of pixels that are adjacent to each
other along the path. (4, 8, or m paths depending
on 4, 8, or m-adjacency)
- Two pixels are said to be connected if there exists a path between them. (4, 8, or m connectivity)
- Euclidean (shortest path)
- D4 distance (city-block path)
- D8 distance (chessboard path)