OPENCV Learning License Plate Extraction

License plate recognition is divided into two steps, one is the license plate extraction, but character recognition.

Here is the license plate extraction.

VS2010.

OpenCV249.

Load Image char * path = "D:\\picture\\06.jpg"; Iplimage * frame = cvloadimage (path), if (!frame) return 0;cvnamedwindow ("frame" , 1); Cvshowimage ("Frame", frame);

Mean filter Cvsmooth (frame, frame, Cv_median),//cvsmooth (frame, frame, Cv_gaussian, 3, 3);//Grayscale Map iplimage * Gray = Cvcreateimage (Cvgetsize (frame), frame->depth, 1), Cvcvtcolor (frame, gray, Cv_bgr2gray), Cvnamedwindow ("Gray", 1); Cvshowimage (" Gray ", gray);

Edge detection Iplimage * temp = Cvcreateimage (Cvgetsize (Gray), ipl_depth_16s,1),//x direction gradient, vertical edge Cvsobel (Gray, temp, 2, 0, 3); I Plimage * Sobel = cvcreateimage (cvgetsize (temp), ipl_depth_8u,1), Cvconvertscale (temp, Sobel, 1, 0); Cvnamedwindow (" Sobel ", 1); Cvshowimage (" Sobel ", Sobel);

Binary Iplimage * threshold = Cvcreateimage (Cvgetsize (Sobel), gray->depth, 1); Cvthreshold (Sobel, threshold, 0, 255, cv_ thresh_binary| Cv_thresh_otsu); Cvnamedwindow ("threshold", 1); Cvshowimage ("threshold", threshold);

Morphological Changes Iplconvkernel * kernal;iplimage * morph = cvcreateimage (cvgetsize (Threshold), threshold->depth, 1);//Custom 1x3 The nucleus of the X-directional swelling corrosion kernal = Cvcreatestructuringelementex (3, 1, 1, 0, cv_shape_rect); Cvdilate (threshold, Morph, kernal, 2); 
   
    //x Expansion Unicom Digital Cverode (morph, Morph, kernal, 4);    x corrosion Removal of fragments cvdilate (morph, Morph, kernal, 4);   X expansion Recovery form//Custom 3x1 core for Y-direction expansion corrosion kernal = Cvcreatestructuringelementex (1, 3, 0, 1, cv_shape_rect); Cverode (morph, Morph, K Ernal, 1);    Y corrosion Removal fragments cvdilate (morph, Morph, kernal, 3);   Y Expansion Recovery morphology cvnamedwindow ("erode", 1), Cvshowimage ("Erode", morph);
   

Contour Detection Iplimage * Frame_draw = Cvcreateimage (Cvgetsize (frame), frame->depth, Frame->nchannels), cvcopy (frame, Frame_draw);  Cvmemstorage * storage = cvcreatememstorage (0);   CVSEQ * Contour = 0;   int count = cvfindcontours (morph, storage, &contour, sizeof (Cvcontour), Cv_retr_ccomp, cv_chain_approx_simple);   CVSEQ * _contour = contour;   for (; Contour! = 0; contour = contour->h_next) {Double Tmparea = fabs (Cvcontourarea (contour)); Cvrect arect = cvboundingrect (contour, 0);  if (Tmparea > (frame->height*frame->width)/10) {cvseqremove (contour,0);//Remove an area less than the set value of the contour, 1/10 continue;  } if (Arect.width < (arect.height*2)) {cvseqremove (contour,0);//Remove contour continue with a width-to-height ratio less than the set value;  }if ((Arect.width/arect.height) > 4) {cvseqremove (contour,0);//Remove contour continue with a width-to-height ratio less than the set value; }if ((Arect.height * arect.width) < ((Frame->height * frame->width)/100)) {cvseqremove (contour,0);//  Remove contour continue with a wide height ratio less than the set value; }cvscalar color = Cv_rgb (255, 0, 0); CvdrawcontouRS (frame_draw, contour, color, color, 0, 1, 8);//Draw external and internal contour}cvnamedwindow ("contour", 1); Cvshowimage ("Contour", Frame_draw); 

Here is the character segmentation and recognition.

OPENCV Learning License Plate Extraction