perspective-transform/opencv-perspective-transform.c

   1 /*
   2  * opencv-perspective-transform - Example program for cvWarpPerspective()
   3  *
   4  * Copyright (C) 2013  Antonio Ospite <ospite@studenti.unina.it>
   5  *
   6  * This program is free software: you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation, either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <stdio.h>
  21 #include <errno.h>
  22 #include <opencv2/core/core_c.h>
  23 #include <opencv2/highgui/highgui_c.h>
  24 #include <opencv2/imgproc/imgproc_c.h>
  25
  26 #define WIDTH 800
  27 #define HEIGHT 480
  28
  29 #define X_CORRECTION 200
  30
  31 int main(int argc, char *argv[])
  32 {
  33         int ret;
  34         IplImage *image;
  35         IplImage *transformed_image;
  36         CvRect viewport;
  37         CvPoint2D32f src[4];
  38         CvPoint2D32f dst[4];
  39         CvMat *perspective_matrix;
  40
  41         if (argc != 2) {
  42                 fprintf(stderr, "usage: %s <image>\n", argv[0]);
  43                 ret = -EINVAL;
  44                 goto out;
  45         }
  46
  47         image = cvLoadImage(argv[1], CV_LOAD_IMAGE_COLOR);
  48         if (!image) {
  49                 fprintf(stderr, "Cannot load image\n");
  50                 ret = -EINVAL;
  51                 goto out;
  52         }
  53
  54         cvNamedWindow("Viewport", 0);
  55         cvResizeWindow("Viewport", WIDTH, HEIGHT);
  56
  57         /* Transform only a part of the whole image */
  58         viewport.x = 0;
  59         viewport.y = 0;
  60         viewport.width = WIDTH;
  61         viewport.height = HEIGHT;
  62         cvSetImageROI(image, viewport);
  63
  64         /* Calculate the perspective transform */
  65         src[0].x = 0;
  66         src[0].y = 0;
  67         src[1].x = WIDTH;
  68         src[1].y = 0;
  69         src[2].x = WIDTH;
  70         src[2].y = HEIGHT;
  71         src[3].x = 0;
  72         src[3].y = HEIGHT;
  73
  74         dst[0].x = X_CORRECTION;
  75         dst[0].y = 0;
  76         dst[1].x = WIDTH - X_CORRECTION;
  77         dst[1].y = 0;
  78         dst[2].x = WIDTH;
  79         dst[2].y = HEIGHT;
  80         dst[3].x = 0;
  81         dst[3].y = HEIGHT;
  82
  83         perspective_matrix = cvCreateMat(3, 3, CV_64F);
  84         if (!perspective_matrix) {
  85                 fprintf(stderr, "Cannot create matrix\n");
  86                 ret = -EINVAL;
  87                 goto out_destroy_window;
  88         }
  89
  90         perspective_matrix = cvGetPerspectiveTransform(src, dst,
  91                                                        perspective_matrix);
  92
  93         /* Create a new image and apply the perspective transform */
  94         transformed_image = cvCreateImage(cvSize(WIDTH, HEIGHT), image->depth,
  95                                           image->nChannels);
  96         if (!transformed_image) {
  97                 fprintf(stderr, "Cannot create transformed image\n");
  98                 ret = -EINVAL;
  99                 goto out_release_mat;
 100         }
 101
 102         cvWarpPerspective(image, transformed_image, perspective_matrix,
 103                           CV_INTER_LINEAR | CV_WARP_FILL_OUTLIERS,
 104                           cvScalarAll(0));
 105
 106         cvShowImage("Viewport", transformed_image);
 107
 108         cvWaitKey(0);
 109
 110         ret = 0;
 111
 112 out_release_mat:
 113         cvReleaseMat(&perspective_matrix);
 114 out_destroy_window:
 115         cvDestroyWindow("Viewport");
 116         cvReleaseImage(&image);
 117 out:
 118         return ret;
 119 }