Vision Processing with the Canny Edge Detection Reference Design

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ID 683433
Date 2/14/2015
Public
Document Table of Contents
Document Table of Contents x
1. Vision Processing with the Canny Edge Detection Reference Design
1. Vision Processing with the Canny Edge Detection Reference Design x
1.1. About Canny Edge Detection 1.2. About the Canny Edge Detection Reference Design 1.3. Getting Started with the Canny Edge Reference Design 1.4. Canny Edge Detection Reference Design Block Description 1.5. Stream-to-Memory Conversion 1.6. Latency and Throughput 1.7. Canny Edge Reference Design Resource Usage
1.3. Getting Started with the Canny Edge Reference Design x
1.3.1. Hardware and Software Requirements 1.3.2. Connecting the Hardware to Use the Canny Edge Reference Design 1.3.3. Loading the Canny Edge Reference Design FPGA Image with the SD Card Image 1.3.4. Canny Edge Reference Design Initial Startup Problems 1.3.5. Controlling the FPGA Flow of the Canny Edge Reference Design 1.3.6. Capturing the Pixel Stream 1.3.7. Programming the FPGA with the Canny Edge Reference Design 1.3.8. Initializing the ARM Processor
1.4. Canny Edge Detection Reference Design Block Description x
1.4.1. Greyscale Conversion 1.4.2. Gaussian Blurring 1.4.3. Sobel Edge Intensity 1.4.4. Nonmaximal Suppression 1.4.5. Double Threshold 1.4.6. Edge Linking
1.5. Stream-to-Memory Conversion x
1.5.1. FPGA and ARM Processor Clock Domains 1.5.2. HPS SDRAM Partitions 1.5.3. Frame Buffering 1.5.4. Operating System and Video Driver 1.5.5. About the Edge-linking Algorithm
1. Vision Processing with the Canny Edge Detection Reference Design

1.4.5. Double Threshold

Applying a double threshold classifies edge pixels from the nonmaximal suppression output as not an edge, weak edge or strong edge.

Some of the edge pixels might be caused by noise and color variations or texturing artefacts. The design uses two thresholds to discern between a true edge and a pseudo edge. The design classifies pixel edge intensities below the low threshold value as not an edge; those between the low and high threshold as weak edges. The design classifies those above the high threshold value as strong edges. The design gives strong edge pixels the maximum value of 255; weak edge pixels the high threshold value. Pixels that the design reclassifies as not an edge are suppressed to 0.

Level Two Title