/* 
 * opencv-perspective-transform - Example program for cvWarpPerspective()
 *
 * Copyright (C) 2013  Antonio Ospite <ospite@studenti.unina.it>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <errno.h>
#include <opencv2/core/core_c.h>
#include <opencv2/highgui/highgui_c.h>
#include <opencv2/imgproc/imgproc_c.h>

#define WIDTH 800
#define HEIGHT 480

#define X_CORRECTION 200

int main(int argc, char *argv[])
{
	int ret;
	IplImage *image;
	IplImage *transformed_image;
	CvRect viewport;
	CvPoint2D32f src[4];
	CvPoint2D32f dst[4];
	CvMat *perspective_matrix;

	if (argc != 2) {
		fprintf(stderr, "usage: %s <image>\n", argv[0]);
		ret = -EINVAL;
		goto out;
	}

	image = cvLoadImage(argv[1], CV_LOAD_IMAGE_COLOR);
	if (!image) {
		fprintf(stderr, "Cannot load image\n");
		ret = -EINVAL;
		goto out;
	}

	cvNamedWindow("Viewport", 0);
	cvResizeWindow("Viewport", WIDTH, HEIGHT);

	/* Transform only a part of the whole image */
	viewport.x = 0;
	viewport.y = 0;
	viewport.width = WIDTH;
	viewport.height = HEIGHT;
	cvSetImageROI(image, viewport);

	/* Calculate the perspective transform */
	src[0].x = 0;
	src[0].y = 0;
	src[1].x = WIDTH;
	src[1].y = 0;
	src[2].x = WIDTH;
	src[2].y = HEIGHT;
	src[3].x = 0;
	src[3].y = HEIGHT;

	dst[0].x = X_CORRECTION;
	dst[0].y = 0;
	dst[1].x = WIDTH - X_CORRECTION;
	dst[1].y = 0;
	dst[2].x = WIDTH;
	dst[2].y = HEIGHT;
	dst[3].x = 0;
	dst[3].y = HEIGHT;

	perspective_matrix = cvCreateMat(3, 3, CV_64F);
	if (!perspective_matrix) {
		fprintf(stderr, "Cannot create matrix\n");
		ret = -EINVAL;
		goto out_destroy_window;
	}

	perspective_matrix = cvGetPerspectiveTransform(src, dst,
						       perspective_matrix);

	/* Create a new image and apply the perspective transform */
	transformed_image = cvCreateImage(cvSize(WIDTH, HEIGHT), image->depth,
					  image->nChannels);
	if (!transformed_image) {
		fprintf(stderr, "Cannot create transformed image\n");
		ret = -EINVAL;
		goto out_release_mat;
	}

	cvWarpPerspective(image, transformed_image, perspective_matrix,
			  CV_INTER_LINEAR | CV_WARP_FILL_OUTLIERS,
			  cvScalarAll(0));

	cvShowImage("Viewport", transformed_image);

	cvWaitKey(0);

	ret = 0;

out_release_mat:
	cvReleaseMat(&perspective_matrix);
out_destroy_window:
	cvDestroyWindow("Viewport");
	cvReleaseImage(&image);
out:
	return ret;
}