• opencv入门笔记之二 操作图像像素点


    voidsalt(Mat &image, int n){

    for (int k = 0; k < n; k++){

    int i = rand() % image.cols;

    int j = rand() % image.rows;

    // rand() ranges from 0 to int.max if the denominator is large its not

    // uniform distribution

    if (image.channels() == 1){

    // 255 means white

    image.at<uchar>(j, i) = 255;

    }

    else if (image.channels() == 3){

    //color image has 3 channels : blue yellow red in scale form

    image.at<Vec3b>(j, i)[0] = 255;

    image.at<Vec3b>(j, i)[1] = 255;

    image.at<Vec3b>(j, i)[2] = 255;

    }

    }        

    }

    Then

    // reducethe quality of each pixel

    voidcolorReduce(Mat &image, int div = 64){

    int nl = image.rows;

    int nc = image.cols*image.channels();

    for (int i = 0; i < nl; i++){

    uchar* data = image.ptr<uchar>(i);

    // .ptr is more efficient than .at

    for (int j = 0; j < nc; j++){

    data[j] = data[j] / div*div + div / 2;

    //another way is to use bit operator which is a very efficientalternative

    // data[j]=(data[j]&(0xFF<<n))+div/2;

    }

    }

    }

     

     

    2/4/2015 11:34 AM - Screen Clipping

    If u wanna haveinput and output in the method

    It can be wirttenlike    void colorReduce(const Mat  &image, Mat &result, int div=64);

    To a continuous line

    Image.reshape(1,rows*cols);

               channel           newrows

    &image.at(j,i)

    Means data =image.data+ j*image.step+i*image.elemSize()

    Using  iterator toaccess pixels

    Mat_<Vec3b>::iteratorit = image.begin<Vec3b>(), itend = image.end<Vec3b>();

    It++

    (*it)[0]

    Its convenient  but the pointer type is the fastest

    In the following waywe can count time is ms;

    double duration = static_cast<double>(getTickCount());

    colorReduce(image);

    duration = static_cast<double>(getTickCount()) - duration;

    duration /= getTickFrequency();

    void sharpen(Mat &image,Mat &result){

    result.create(image.size(), image.type());

    for (int i = 1; i < image.rows-1;i++)

    {

    const uchar* previous = image.ptr<const uchar>(i - 1);

    const uchar* current = image.ptr<const uchar>(i);

    const uchar* next = image.ptr< const uchar>(i + 1);

    uchar* output = result.ptr<uchar>(i);

    for (int j = 1; j < image.cols - 1; j++){

    *output++ =saturate_cast<uchar>( current[j] * 5 - current[j -1] - current[j + 1] - previous[j] - next[j]);

    //saturate means 0<= uchar<=255

    }

    }

    result.row(0).setTo(Scalar(0));

    result.row(result.rows-1).setTo(Scalar(0));

    result.col(0).setTo(Scalar(0));

    result.col(result.cols-1).setTo(Scalar(0));

    // deal with the whole row or column

    }

    Add onepic to another

    // c[i]=a[i]+b[i];

       cv::add(imageA,imageB,resultC);

       // c[i]= a[i]+k;

       cv::add(imageA,cv::Scalar(k),resultC);

       // c[i]= k1*a[1]+k2*b[i]+k3;

      cv::addWeighted(imageA,k1,imageB,k2,k3,resultC);

       // c[i]= k*a[1]+b[i];

       cv::scaleAdd(imageA,k,imageB,resultC);

    Add weightis overloaded

    result=0.7*image1+0.9*image2;

    image=(image&cv::Scalar(mask,mask,mask))

                     +cv::Scalar(div/2,div/2,div/2);

    Split andmerge

     // create vector of 3 images

       std::vector<cv::Mat> planes;

       // split 1 3-channel image into 3 1-channelimages

       cv::split(image1,planes);

       // add to blue channel

       planes[0]+= image2;

       // merge the 3 1-channel images into 13-channel image

       cv::merge(planes,result);

    ROI

    Rect(200,250,logoImage.cols,logoImage.rows)

     

    cv::MatimageROI= image(cv::Range(270,270+logo.rows),

                           cv::Range(385,385+logo.cols))

    image.colRange(start,end);

    intmain(){

    Mat logo= imread("logo.jpg");

    Mat image = imread("rain.jpg");

    //the same size

    Mat ROI;

    Mat result;

    imshow("old", image);

    result.create(image.size(), image.type());

    double duration = static_cast<double>(getTickCount());

    //

    ROI = image(Rect(0, 0, logo.cols,logo.rows));

    addWeighted(logo, 0.3,ROI, 1.0, 0.0,ROI);

    //

    duration = static_cast<double>(getTickCount()) - duration;

    duration /= getTickFrequency();

    cout << duration;

    imshow("new",image);

    waitKey(0);

    }

     

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  • 原文地址:https://www.cnblogs.com/Pomodori/p/4316621.html
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