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219 lines
11 KiB
C++
219 lines
11 KiB
C++
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/*
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#
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# File : edge_explorer2d.cpp
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# ( C++ source file )
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#
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# Description : Real time edge detection while moving a ROI
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# (rectangle of interest) over the original image.
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# This file is a part of the CImg Library project.
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# ( http://cimg.eu )
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#
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# Copyright : Orges Leka
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# ( oleka(at)students.uni-mainz.de )
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#
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# License : CeCILL v2.0
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# ( http://www.cecill.info/licences/Licence_CeCILL_V2-en.html )
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#
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# This software is governed by the CeCILL license under French law and
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# abiding by the rules of distribution of free software. You can use,
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# modify and/ or redistribute the software under the terms of the CeCILL
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# license as circulated by CEA, CNRS and INRIA at the following URL
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# "http://www.cecill.info".
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#
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# As a counterpart to the access to the source code and rights to copy,
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# modify and redistribute granted by the license, users are provided only
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# with a limited warranty and the software's author, the holder of the
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# economic rights, and the successive licensors have only limited
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# liability.
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#
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# In this respect, the user's attention is drawn to the risks associated
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# with loading, using, modifying and/or developing or reproducing the
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# software by the user in light of its specific status of free software,
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# that may mean that it is complicated to manipulate, and that also
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# therefore means that it is reserved for developers and experienced
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# professionals having in-depth computer knowledge. Users are therefore
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# encouraged to load and test the software's suitability as regards their
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# requirements in conditions enabling the security of their systems and/or
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# data to be ensured and, more generally, to use and operate it in the
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# same conditions as regards security.
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#
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# The fact that you are presently reading this means that you have had
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# knowledge of the CeCILL license and that you accept its terms.
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#
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*/
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#include "CImg.h"
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using namespace cimg_library;
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#ifndef cimg_imagepath
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#define cimg_imagepath "img/"
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#endif
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// Main procedure
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//----------------
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int main(int argc, char** argv) {
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// Usage of the program displayed at the command line
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cimg_usage("Real time edge detection with CImg. (c) Orges Leka");
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// Read command line arguments
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// With cimg_option we can get a new name for the image which is to be loaded from the command line.
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const char* img_name = cimg_option("-i", cimg_imagepath "parrot.ppm","Input image.");
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double
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alpha = cimg_option("-a",1.0,"Blurring the gradient image."),
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thresL = cimg_option("-tl",13.5,"Lower thresholding used in Hysteresis."),
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thresH = cimg_option("-th",13.6,"Higher thresholding used in Hysteresis.");
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const unsigned int
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mode = cimg_option("-m",1,"Detection mode: 1 = Hysteresis, 2 = Gradient angle."),
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factor = cimg_option("-s",80,"Half-size of edge-explorer window.");
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cimg_help("\nAdditional notes : user can press following keys on main display window :\n"
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" - Left arrow : Decrease alpha.\n"
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" - Right arrow : Increase alpha.\n");
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// Construct a new image called 'edge' of size (2*factor,2*factor)
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// and of type 'unsigned char'.
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CImg<unsigned char> edge(2*factor,2*factor);
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CImgDisplay disp_edge(512,512,"Edge Explorer");
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// Load the image with the name 'img_name' into the CImg 'img'.
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// and create a display window 'disp' for the image 'img'.
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const CImg<unsigned char> img = CImg<float>::get_load(img_name).norm().normalize(0,255);
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CImgDisplay disp(img,"Original Image");
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// Begin main interaction loop.
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int x = 0, y = 0;
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bool redraw = false;
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while (!disp.is_closed() && !disp.is_keyQ() && !disp.is_keyESC()) {
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disp.wait(100);
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if (disp.button()&1) { alpha+=0.05; redraw = true; }
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if (disp.button()&2) { alpha-=0.05; redraw = true; }
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if (disp.wheel()) { alpha+=0.05*disp.wheel(); disp.set_wheel(); redraw = true; }
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if (alpha<0) alpha = 0;
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if (disp_edge.is_resized()) { disp_edge.resize(); redraw = true; }
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if (disp_edge.is_closed()) disp_edge.show();
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if (disp.is_resized()) disp.resize(disp);
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if (disp.mouse_x()>=0) {
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x = disp.mouse_x(); // Getting the current position of the mouse
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y = disp.mouse_y(); //
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redraw = true; // The image should be redrawn
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}
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if (redraw) {
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disp_edge.set_title("Edge explorer (alpha=%g)",alpha);
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const int
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x0 = x - factor, y0 = y - factor, // These are the coordinates for the red rectangle
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x1 = x + factor, y1 = y + factor; // to be drawn on the original image
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const unsigned char
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red[3] = { 255,0,0 }, //
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black[3] = { 0,0,0 }; // Defining the colors we need for drawing
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(+img).draw_rectangle(x0,y0,x1,y1,red,1.0f,0x55555555U).display(disp);
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//^ We draw the red rectangle on the original window using 'draw_line'.
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// Then we display the result via '.display(disp)' .
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// Observe, that the color 'red' has to be of type 'const unsigned char',
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// since the image 'img' is of type 'const CImg<unsigned char>'.
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//'normalize' is used to get a greyscaled image.
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CImg<> visu_bw = CImg<>(img).get_crop(x0,y0,x1,y1).get_norm().normalize(0,255).resize(-100,-100,1,2,2);
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// get_crop(x0,y0,x1,y1) gets the rectangle we are interested in.
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edge.fill(255); // Background color in the edge-detection window is white
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// grad[0] is the gradient image of 'visu_bw' in x-direction.
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// grad[1] is the gradient image of 'visu_bw' in y-direction.
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CImgList<> grad(visu_bw.blur((float)alpha).normalize(0,255).get_gradient());
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// To avoid unnecessary calculations in the image loops:
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const double
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pi = cimg::PI,
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p8 = pi/8.0, p38 = 3.0*p8,
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p58 = 5.0*p8, p78 = 7.0*p8;
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cimg_forXY(visu_bw,s,t) {
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// We take s,t instead of x,y, since x,y are already used.
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// s corresponds to the x-ordinate of the pixel while t corresponds to the y-ordinate.
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if ( 1 <= s && s <= visu_bw.width() - 1 && 1 <= t && t <=visu_bw.height() - 1) { // if - good points
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double
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Gs = grad[0](s,t), //
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Gt = grad[1](s,t), // The actual pixel is (s,t)
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Gst = cimg::abs(Gs) + cimg::abs(Gt), //
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// ^-- For efficient computation we observe that |Gs|+ |Gt| ~=~ sqrt( Gs^2 + Gt^2)
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Gr, Gur, Gu, Gul, Gl, Gdl, Gd, Gdr;
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// ^-- right, up right, up, up left, left, down left, down, down right.
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double theta = std::atan2(std::max(1e-8,Gt),Gs) + pi; // theta is from the interval [0,Pi]
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switch(mode) {
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case 1: // Hysterese is applied
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if (Gst>=thresH) { edge.draw_point(s,t,black); }
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else if (thresL <= Gst && Gst < thresH) {
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// Neighbourhood of the actual pixel:
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Gr = cimg::abs(grad[0](s + 1,t)) + cimg::abs(grad[1](s + 1,t)); // right
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Gl = cimg::abs(grad[0](s - 1,t)) + cimg::abs(grad[1](s - 1,t)); // left
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Gur = cimg::abs(grad[0](s + 1,t + 1)) + cimg::abs(grad[1](s + 1,t + 1)); // up right
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Gdl = cimg::abs(grad[0](s - 1,t - 1)) + cimg::abs(grad[1](s - 1,t - 1)); // down left
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Gu = cimg::abs(grad[0](s,t + 1)) + cimg::abs(grad[1](s,t + 1)); // up
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Gd = cimg::abs(grad[0](s,t - 1)) + cimg::abs(grad[1](s,t - 1)); // down
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Gul = cimg::abs(grad[0](s - 1,t + 1)) + cimg::abs(grad[1](s - 1,t + 1)); // up left
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Gdr = cimg::abs(grad[0](s + 1,t - 1)) + cimg::abs(grad[1](s + 1,t - 1)); // down right
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if (Gr>=thresH || Gur>=thresH || Gu>=thresH || Gul>=thresH
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|| Gl>=thresH || Gdl >=thresH || Gu >=thresH || Gdr >=thresH) {
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edge.draw_point(s,t,black);
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}
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};
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break;
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case 2: // Angle 'theta' of the gradient (Gs,Gt) at the point (s,t)
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if(theta >= pi)theta-=pi;
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//rounding theta:
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if ((p8 < theta && theta <= p38 ) || (p78 < theta && theta <= pi)) {
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// See (*) below for explanation of the vocabulary used.
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// Direction-pixel is (s + 1,t) with corresponding gradient value Gr.
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Gr = cimg::abs(grad[0](s + 1,t)) + cimg::abs(grad[1](s + 1,t)); // right
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// Contra-direction-pixel is (s - 1,t) with corresponding gradient value Gl.
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Gl = cimg::abs(grad[0](s - 1,t)) + cimg::abs(grad[1](s - 1,t)); // left
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if (Gr < Gst && Gl < Gst) {
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edge.draw_point(s,t,black);
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}
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}
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else if ( p8 < theta && theta <= p38) {
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// Direction-pixel is (s + 1,t + 1) with corresponding gradient value Gur.
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Gur = cimg::abs(grad[0](s + 1,t + 1)) + cimg::abs(grad[1](s + 1,t + 1)); // up right
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// Contra-direction-pixel is (s-1,t-1) with corresponding gradient value Gdl.
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Gdl = cimg::abs(grad[0](s - 1,t - 1)) + cimg::abs(grad[1](s - 1,t - 1)); // down left
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if (Gur < Gst && Gdl < Gst) {
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edge.draw_point(s,t,black);
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}
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}
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else if ( p38 < theta && theta <= p58) {
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// Direction-pixel is (s,t + 1) with corresponding gradient value Gu.
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Gu = cimg::abs(grad[0](s,t + 1)) + cimg::abs(grad[1](s,t + 1)); // up
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// Contra-direction-pixel is (s,t - 1) with corresponding gradient value Gd.
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Gd = cimg::abs(grad[0](s,t - 1)) + cimg::abs(grad[1](s,t - 1)); // down
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if (Gu < Gst && Gd < Gst) {
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edge.draw_point(s,t,black);
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}
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}
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else if (p58 < theta && theta <= p78) {
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// Direction-pixel is (s - 1,t + 1) with corresponding gradient value Gul.
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Gul = cimg::abs(grad[0](s - 1,t + 1)) + cimg::abs(grad[1](s - 1,t + 1)); // up left
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// Contra-direction-pixel is (s + 1,t - 1) with corresponding gradient value Gdr.
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Gdr = cimg::abs(grad[0](s + 1,t - 1)) + cimg::abs(grad[1](s + 1,t - 1)); // down right
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if (Gul < Gst && Gdr < Gst) {
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edge.draw_point(s,t,black);
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}
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};
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break;
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} // switch
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} // if good-points
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} // cimg_forXY */
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edge.display(disp_edge);
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}// if redraw
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} // while
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return 0;
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}
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// (*) Comments to the vocabulary used:
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// If (s,t) is the current pixel, and G=(Gs,Gt) is the gradient at (s,t),
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// then the _direction_pixel_ of (s,t) shall be the one of the eight neighbour pixels
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// of (s,t) in whose direction the gradient G shows.
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// The _contra_direction_pixel is the pixel in the opposite direction in which the gradient G shows.
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// The _corresponding_gradient_value_ of the pixel (x,y) with gradient G = (Gx,Gy)
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// shall be |Gx| + |Gy| ~=~ sqrt(Gx^2 + Gy^2).
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