Method for detecting door gap of vehicle body based on edge detection

A method for detecting a door gap of a vehicle body based on edge detection, specifically comprising the following steps:

• step 1:
• building a vehicle body door gap detection device, and detecting a vehicle body door gap image, wherein the detection device comprises a light controller, a charge coupled device (CCD) camera, a laser line emitter, a communication network, and a computer processing system;
• step 2:
• performing image filtering, specifically:
• first graying a detected vehicle body door gap image, and then filtering a grayed image;
• step 3:
• smoothing a filtered image with a first-order partial derivative of a Gaussian function, calculating gradients and directions of the image with a finite difference of the first-order partial derivative to form a gradient image, and taking a Roberts operator as an edge detection operator;
• step 4:
• performing non-maximum suppression (NMS) on gradient magnitudes in the gradient image, and only retaining local maxima to obtain discrete points of a gradient edge contour image;
• step 5:
• giving a low threshold and a high threshold, marking points with gradient values greater than the high threshold as strong edge pixels, and as anchor points in the image, and setting a pixel for a point with a gradient value less than the low threshold as 0, and connecting the anchor points to form an edge image;
• and
• step 6:
• extracting a feature point of the edge image, matching the feature point with a laser-marked image window, finding a position perpendicular to the door gap, calculating a Manhattan distance at the window, taking a maximum Manhattan distance in the window as a Manhattan width for the door gap of the vehicle body, determining a width of the door gap of the vehicle body, and obtaining a minimum for the width of the door gap according to the width of the door gap in multiple frames of images.