image 1 an image is a two dimensional function f(x,y) where x and y are spatial coordinates and f at...

57
IMAGE 1 An image is a two dimensional Function f(x,y) where x and y are spatial coordinates And f at any x,y is related to the brightness at that point A digital image is a 2D representation of a continuous image by a 2D array of discrete

Post on 21-Dec-2015

232 views

Category:

Documents


1 download

TRANSCRIPT

IMAGE 1

An image is a two dimensionalFunction f(x,y) where x and y are spatial coordinatesAnd f at any x,y is related to the brightness at that point

A digital image is a 2D representation of a continuous image by a 2D array of discrete samples

Each element of the 2D array is a pixel.

Definition

Histograms count the number of occurrences of each possible value

H D( )

Count Grey level

Properties

• Sum of all values in the histogram equals the total number of pixels

H D( )dD0

∫ =imagearea

Properties

• Sum of all values between a and b equals the area of all objects in that range

H D( )dDa

b

∫ =areaofall partsa≤I ≤b

Properties

• Integrated optical density

• Mean greylevel

IOD= DH D( )dD0

MGL=IOD area

Application: Adjusting Camera Parameters

• Too bright - lots of pixels at 255 (or max)

• Too dark - lots of pixels at 0

• Gain too low - not enough of the range used

Application: Segmentation

• Can be used to separate bright objects from dark background (or vice versa)

Normalizing Histograms

• Probability density function = histogram normalized by area

p D( )=1AH D( )

Cumulative Histograms

• Counts pixels with values up to and including the specified value

C a( ) = H D( )dD0

a

Cumulative Density Functions

• Normalized cumulative histograms

P a( )= p D( )dD0

a

∫ =1AC a( )

IMAGE 1

Image 1: Bright

Image 1: Dark

Image 1: Low contrast

Image 1: High contrast

RESOLUTION

INTERPOLATION

HISTOGRAM EQUALIZATION

THRESHOLDING

104

199

34

137

Inverted

SMOOTH 3

MEDIAN 3

SMOOTH 7

MEDIAN 5