ImgP Ch3

What does an image sensor do?

Converts optical energy into electrical energy or a digital image

What are the two parts of image formation?

Geometry and physics of light

What determines the location of a point in the image plane?

Geometry

What determines the brightness of a point in the image plane?

Physics of light

What forms an image on the retina?

The eye lens

What principle is used to relate object size and retinal image size?

Similar triangles

What is the magnification formula?

m = hi/ho = di/do

What does ho represent?

Real object height

What does hi represent?

Image height on the sensor or retina

What does do represent?

Distance to the object

What does di represent?

Distance from lens to image plane (retina)

If magnification increases, what happens to image size?

Image size increases

What happens if film is placed in front of an object without a lens system?

Blurring occurs

What is an aperture?

A small opening that allows light to pass through

Why is an aperture used in cameras?

To reduce blurring

What is the effect of a large aperture?

More blur due to improper focusing

What is the effect of a small aperture?

Less blur but less light enters the camera

What additional effect occurs with very small apertures?

Diffraction

What is diffraction?

The spreading of light when it passes through a small opening

Why can't the aperture be made infinitely small?

Because diffraction increases

What causes image blur with a large aperture?

Light spreads across the image plane

What are the two main components of an image function f(x,y)?

Illumination and reflectance

What is the image formation equation?

f(x,y)=i(x,y)r(x,y)

What does i(x,y) represent?

Illumination component

What does r(x,y) represent?

Reflectance component

What is the range of reflectance?

0 ≤ r(x,y) ≤ 1

What does reflectance value 0 mean?

Total absorption

What does reflectance value 1 mean?

Total reflection

What determines the illumination component?

The illumination source

What determines the reflectance component?

The characteristics of the objects

What does l=f(x,y) represent?

Image intensity or gray level

What is the intensity scale?

The interval [Lmin, Lmax]

What is a digital image?

A sampled and quantized version of a continuous image

What are the two processes required to digitize an image?

Sampling and quantization

What is sampling?

Digitizing coordinate values

What is quantization?

Digitizing amplitude/intensity values

Which process affects spatial resolution?

Sampling

Which process affects intensity resolution?

Quantization

What does image sampling convert?

Continuous coordinates into discrete coordinates

What does image quantization convert?

Continuous intensity values into discrete intensity levels

What is represented by M in an image matrix?

Number of rows

What is represented by N in an image matrix?

Number of columns

What is a pixel?

An image element or picture element

What is another name for a pixel?

Pel

What is the coordinate range for x in an M×N image?

0 to M−1

What is the coordinate range for y in an M×N image?

0 to N−1

How is the center of an image calculated?

(floor(M/2), floor(N/2))

What is the formula for the number of intensity levels?

L = 2^k

What does k represent in L=2^k?

Number of bits per pixel

What is an 8-bit image?

An image with 256 intensity levels

How many intensity levels does a 6-bit image have?

64

How many intensity levels does a 7-bit image have?

128

How many intensity levels does a 10-bit image have?

1024

What is the intensity range of an 8-bit grayscale image?

0 to 255

How many gray levels are in an 8-bit image?

256

How many gray levels are in a 6-bit image?

64

What is the formula for image storage in bits?

b = M × N × k

What does b represent in image storage?

Total number of bits

How many bits are required to store a 512×512 image with 8 bits/pixel?

2,097,152 bits

What is spatial resolution?

The smallest discernible detail in an image

What unit is commonly used for spatial resolution?

DPI (dots per inch)

What does DPI stand for?

Dots per inch

Which image has higher spatial resolution: 200 dpi or 400 dpi?

400 dpi

What is intensity resolution?

The smallest discernible change in intensity

How is intensity resolution commonly expressed?

Number of bits used for quantization

What is the intensity resolution of a 256-level image?

8 bits

What happens when spatial resolution increases?

More image detail is captured

What happens when intensity resolution increases?

More gray levels are available

What is interpolation?

Estimating values at unknown locations using known data

When is interpolation used?

Zooming, shrinking, rotating, and geometric correction

What is the simplest interpolation method?

Nearest neighbor interpolation

How does nearest neighbor interpolation work?

Uses the value of the nearest pixel

Does nearest neighbor use averaging?

No

How does bilinear interpolation work?

Uses weighted averages of four neighboring pixels

How many neighboring pixels are used in bilinear interpolation?

4

How many neighboring pixels are used in bicubic interpolation?

16

Which interpolation method generally produces the smoothest results?

Bicubic

Which interpolation method is fastest?

Nearest neighbor

Which interpolation method may create blocky images?

Nearest neighbor

What determines image storage requirements?

Rows, columns, and bits per pixel

What is the formula for image size?

Rows × Columns × Bits per Pixel

How many bits per pixel does an RGB image with 8 bits per channel have?

24 bits/pixel

How many channels are used in RGB images?

3

What are the RGB channels?

Red, Green, Blue

What is a set?

A collection of distinct objects

How is membership in a set denoted?

a ∈ A

How is non-membership in a set denoted?

a ∉ A

What is the empty set symbol?

∅

What is the complement of a set?

Elements not belonging to the set

What is A−B?

Elements in A but not in B

What does A∩B represent?

Intersection

What does A∪B represent?

Union

What is the relationship between A−B and complements?

A−B = A∩Bc

What is image complement used for?

Creating image negatives

What are spatial operations performed on?

Pixels directly

What are the three categories of spatial operations?

Single-pixel, neighborhood, geometric transformations

What is a single-pixel operation?

An operation applied independently to each pixel

What is a neighborhood operation?

An operation using surrounding pixels

What are geometric transformations used for?

Changing pixel locations

What are geometric transformations also called?

Rubber-sheet transformations