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Pattern RecognitionMrs. Andleeb Y. KhanLecture 03BCS-VII
Image enhancement using
Point Processing1. What is point processing?2. Negative images3. Thresholding4. Logarithmic Transforms5. Power Law Transform6. Grey Level Slicing7. Bit Plane Slicing
Image enhancement• Goal: To modify an image so that its utilization on a particular
application is enhanced.• A set of ad hoc tools applicable based on viewer’s specific
needs.• No general theory on image enhancement exists.
Spatial & frequency domains• Two broad categories of image enhancement techniques:• Spatial Domain• Pixel Processing
• Grey Level Transformation (Data Independent)• Histogram Processing (Data Dependent)• Arithmetic Operations
• Mask-based Processing• Frequency Domain Filtering• Manipulation of Fourier transform or wavelet transform of an
image
Image enhancement
Image enhancement
Image enhancement
Image enhancement
Image histogram The histogram of an image shows us the distribution of
grey levels in the image. Massively useful in image processing, esp. in segmentation.
Histogram example
Spatial domain image enhancement• Most spatial domain
enhancement operations can be reduced to the form
• G(x,y) = T[f(x,y)]• Where f(x,y) is the input image,
g(x,y) is the processed image and T is some operator defined over some neighbourhood of (x,y)
Spatial domain• The operator T can be defined over the set of pixels(x,y) of the
image• The set of neighborhood N(x,y) of each pixel• A set of images f1,f2,f3
From system point of view
Point processing in spatial domain• Operation on the set of image-pixels
Mask processing or filter• Neighborhood is bigger than 1x1 pixel• Use a function of the values of f in a pre-defined
neighborhood of (x,y) to determine the value of g at (x,y)• The value of the mask coefficients determine the nature of the
process• Used in techniques:• Image Sharpening• Image Smoothing
Spatial domain Operation on the set of neighborhoods N(x,y) of each pixel.
Basic grey level transformation
Negative images
Negative images
Negative images...
Logarithmic transformation
Logarithmic transformation
Power law transformations
Power law transformations...
Power law transformation
Power Law Example....
Power Law Example....
Power Law Example....
Power Law Example....
Power Law Example....
Power Law Example....
Power Law Example....
Gamma Correction
Power Law Grey level transform
