Simple Examples For Handling Images With OpenCV

macro(use_cxx11)
  if (CMAKE_VERSION VERSION_LESS "3.1")
    if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
      set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")
    endif ()
  else ()
    set (CMAKE_CXX_STANDARD 11)
  endif ()
endmacro(use_cxx11)

cmake_minimum_required(VERSION 2.8)
project( cvMat )
use_cxx11()
find_package( OpenCV REQUIRED )
add_executable( ${PROJECT_NAME} "main.cpp" )
target_link_libraries( ${PROJECT_NAME} ${OpenCV_LIBS} )

#include <stdio.h>
#include <opencv2/opencv.hpp>

using namespace cv;

int main(int argc, char** argv )
{
    Mat image;
    image = imread( "/Users/weiyang/Desktop/Untitled.png", 1 );

    if ( !image.data )
    {
        printf("No image data \n");
        return -1;
    }
    namedWindow("Display Image", WINDOW_AUTOSIZE );
    imshow("Display Image", image);

    waitKey(0);

    return 0;
}

    Mat greyImage;
    cvtColor(image, greyImage, COLOR_BGR2GRAY);
    imshow("Display greyImage", greyImage);
    imwrite( "/Users/weiyang/Desktop/gregImage.png", greyImage );

    Rect region( 0, 0, image.size().width, (image.size().height + 0.5) / 2.0 );
    Mat upperHalf = image( region );
    imshow("Display upperHalf", upperHalf);

    Mat image;
    image = imread( "/Users/weiyang/Desktop/Untitled.png", 1 );

    if ( !image.data )
    {
        printf("No image data \n");
        return -1;
    }
    namedWindow("Display Image", WINDOW_AUTOSIZE );
    imshow("Display Image", image);

    Mat grey;
    cvtColor(image, grey, COLOR_BGR2GRAY);
    Mat sobelx;
    Sobel(grey, sobelx, CV_32F, 1, 1);

    namedWindow("Display sobelx", WINDOW_AUTOSIZE);
    imshow("Display sobelx", sobelx);

    double minVal, maxVal;
    minMaxLoc(sobelx, &minVal, &maxVal); //find minimum and maximum intensities
    Mat draw;
    sobelx.convertTo(draw, CV_8U, 255.0/(maxVal - minVal), -minVal * 255.0/(maxVal - minVal));
    namedWindow("Display draw", WINDOW_AUTOSIZE);
    imshow("Display draw", draw);