Upload
gerald-potter
View
217
Download
2
Tags:
Embed Size (px)
Citation preview
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 histogram The histogram of an image shows us the distribution of
grey levels in the image. Massively useful in image processing, esp. in segmentation.
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
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