Lecture Digital image processing: Edge detection presents the following content: Introduction, the sobel operator, the prewitt operator, the canny operator, the zero-crossing detector, the unsharp filter.
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Nội dung Text: Lecture Digital image processing: Edge detection - Nguyễn Công Phương
- Nguyễn Công Phương
DIGITAL IMAGE PROCESSING
Edge Detection
- Contents
I. Introduction to Image Processing & Matlab
II. Image Acquisition, Types, & File I/O
III. Image Arithmetic
IV. Affine & Logical Operations, Distortions, & Noise in Images
V. Image Transform
VI. Spatial & Frequency Domain Filter Design
VII. Image Restoration & Blind Deconvolution
VIII. Image Compression
IX. Edge Detection
X. Binary Image Processing
XI. Image Encryption & Watermarking
XII. Image Classification & Segmentation
XIII. Image – Based Object Tracking
XIV. Face Recognition
XV. Soft Computing in Image Processing
sites.google.com/site/ncpdhbkhn 2
- Edge Detection
1. Introduction
2. The Sobel Operator
3. The Prewitt Operator
4. The Canny Operator
5. The Zero-Crossing Detector
6. The Unsharp Filter
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- Introduction
• In some applications, only certain areas of interest
are isolated to be processed for further stages of
processing edge detection.
• Edge: a sudden change of intensity in an image.
• In binary image, an edge corresponds to a sudden
change in intensity level to 1 from 0, & vice
versa.
• Too many edges represent a “rough” image.
• Too few would correspond to a relatively
“smoother” image.
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- Edge Detection
1. Introduction
2. The Sobel Operator
3. The Prewitt Operator
4. The Canny Operator
5. The Zero-Crossing Detector
6. The Unsharp Filter
sites.google.com/site/ncpdhbkhn 5
- The Sobel Operator
• It performs a 2D spatial gradient measurement
on an image and emphasizes regions of high
spatial frequency that correspond to edges.
• Typically, it is used to find the approximate
absolute gradient magnitude at each point in an
input grayscale image.
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- Edge Detection
1. Introduction
2. The Sobel Operator
3. The Prewitt Operator
4. The Canny Operator
5. The Zero-Crossing Detector
6. The Unsharp Filter
sites.google.com/site/ncpdhbkhn 7
- The Prewitt Operator
• Works in a very similar way to the Sobel
operator.
• But uses slightly different kernels.
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- Edge Detection
1. Introduction
2. The Sobel Operator
3. The Prewitt Operator
4. The Canny Operator
5. The Zero-Crossing Detector
6. The Unsharp Filter
sites.google.com/site/ncpdhbkhn 9
- The Canny Operator
• It produces as output an image showing the
positions of tracked intensity discontinuities.
sites.google.com/site/ncpdhbkhn 10
- Edge Detection
1. Introduction
2. The Sobel Operator
3. The Prewitt Operator
4. The Canny Operator
5. The Zero-Crossing Detector
6. The Unsharp Filter
sites.google.com/site/ncpdhbkhn 11
- The Zero-Crossing Detector
• The zero-crossing detector looks for places in
the Laplacian of an image where the value of
the Laplacian passes through zero, that is,
points where the Laplacian changes sign.
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- Edge Detection
1. Introduction
2. The Sobel Operator
3. The Prewitt Operator
4. The Canny Operator
5. The Zero-Crossing Detector
6. The Unsharp Filter
sites.google.com/site/ncpdhbkhn 13
- The Unsharp Filter
• It enhances edges (and other high-frequency
components in an image) via a procedure that
subtracts an unsharp, or smoothed, version of
an image from the original image.
• The unsharp filtering technique is commonly
used in the photographic and printing
industries.
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