Example: img_basic_example

C++ example source code:

/*                    _
                     | |    Mobile Robot Programming Toolkit (MRPT)
 _ __ ___  _ __ _ __ | |_
| '_ ` _ \| '__| '_ \| __|          https://www.mrpt.org/
| | | | | | |  | |_) | |_
|_| |_| |_|_|  | .__/ \__|     https://github.com/MRPT/mrpt/
               | |
               |_|

 Copyright (c) 2005-2026, Individual contributors, see AUTHORS file
 See: https://www.mrpt.org/Authors - All rights reserved.
 SPDX-License-Identifier: BSD-3-Clause
*/

#include <mrpt/gui/CDisplayWindow.h>
#include <mrpt/math/CMatrixF.h>
#include <mrpt/system/CTicTac.h>
#include <mrpt/system/CTimeLogger.h>

#include <iostream>

using namespace mrpt;
using namespace mrpt::gui;
using namespace mrpt::img;
using namespace mrpt::math;
using namespace mrpt::system;
using namespace std;

// MRPT_EXAMPLES_BASE_DIRECTORY provided via compile definition
string myDataDir(MRPT_EXAMPLES_BASE_DIRECTORY + string("img_basic_example/"));

// ------------------------------------------------------
//              TestImageCap
// ------------------------------------------------------
void TestImageConversion()
{
  // BMP -> JPEG conversion tester:
  // --------------------------------
  CImage img;
  CTicTac tictac;
  CTimeLogger timlog;

  tictac.Tic();
  if (!img.loadFromFile(myDataDir + string("frame_color.jpg")))
  {
    cerr << "Cannot load " << myDataDir + string("frame_color.jpg") << "\n";
    return;
  }
  printf("Image loaded in %.03fms\n", 1000 * tictac.Tac());

  if (false)  // A very simple test:
  {
    CDisplayWindow win1("JPEG file, color");
    win1.setPos(10, 10);

    win1.showImage(img);

    std::cout << "Push a key in the console or in the window to continue...";
    win1.waitForKey();
    std::cout << "Done"
              << "\n";

    timlog.enter("grayscale1");
    img = img.grayscale();
    timlog.leave("grayscale1");

    CDisplayWindow win2("JPEG file, gray");
    win2.showImage(img);
    win1.setPos(300, 10);

    std::cout << "Push a key in the console or in the window to continue...";
    win2.waitForKey();
    std::cout << "Done"
              << "\n";

    mrpt::system::pause();
    return;
  }

  CDisplayWindow win1("win1"), win2("win2"), win3("win3"), win4("win4");

  CImage imgSmall(img);
  CImage imgGray;

  for (int i = 0; i < 50; i++)
  {
    timlog.enter("grayscale2");
    imgSmall.grayscale(imgGray);
    timlog.leave("grayscale2");
  }

  CImage imgSmall2 = imgGray.scaleHalf(IMG_INTERP_LINEAR);
  CImage imgSmallRGB = img.scaleHalf(IMG_INTERP_LINEAR);

  // Test some draw capabilities:
  // ---------------------------------
  imgSmall.rectangle({85, 35}, {170, 170}, TColor(255, 0, 0), 10);

  imgSmall.line({550, 75}, {650, 25}, TColor(0, 0, 255));
  imgSmall.line({-10, -20}, {20, 30}, TColor(0, 0, 255));

  CMatrixDouble22 COV;
  COV(0, 0) = 100;
  COV(1, 1) = 50;
  COV(0, 1) = COV(1, 0) = -30;
  imgSmall.ellipseGaussian(COV, 600.0, 50.0, 2, TColor(255, 255, 0), 4);
  imgGray.ellipseGaussian(COV, 100.0, 100.0, 2, TColor(0, 0, 255), 4);

  imgGray.drawImage({50, 40}, imgSmall2);

  // Show the windows now:
  // ------------------------------------------------------
  win1.showImage(imgSmall);
  win1.setPos(0, 0);
  win2.showImage(imgSmall2);
  win2.setPos(810, 0);
  win3.showImage(imgGray);
  win3.setPos(810, 300);
  win4.showImage(imgSmallRGB);
  win4.setPos(300, 400);

  std::cout << "Press any key on 'win4' to exit"
            << "\n";
  win4.waitForKey();

  tictac.Tic();
  bool savedOk = imgGray.saveToFile("frame_out.jpg");
  ASSERT_(savedOk);
  printf("jpeg file saved in %.03fms\n", 1000.0 * tictac.Tac());

  savedOk = imgSmall2.saveToFile("frame_out_small.png");
  ASSERT_(savedOk);

  return;
}

// ------------------------------------------------------
//                      MAIN
// ------------------------------------------------------
int main()
{
  try
  {
    TestImageConversion();
    return 0;
  }
  catch (const std::exception& e)
  {
    std::cerr << "MRPT error: " << mrpt::exception_to_str(e) << "\n";
    return -1;
  }
}