對比OpenCV, QT, ITK庫對圖像像素級的操作

本文以常見的二維BMP圖像爲例，對比OpenCV, QT, ITK庫對圖像像素級的操作。

(1)OpenCV由IplImage對圖像像素級的操作, 要考慮RGB分量;

IplImage* img = cvLoadImage("D:/openCV/Project/readImage/data/binary.bmp");
uchar temp = image->imageData[y * image->widthStep + x];//widthStep = width * 3, 對應RGB3個分量

(2)QT由QImage對圖像像素級的操作，要考慮ARGB分量;

 QImage* img = new QImage();
 img->load("D:/openCV/Project/readImage/data/binary.bmp");
 unsigned char* data = img->bits();//獲取圖像像素字節數據的首地址

(3)ITK由reader指針對圖像像素級的操作，不要考慮RGB分量;

 typedef itk::ImageFileReader< InputImageType  >  ReaderType;
 ReaderType::Pointer reader = ReaderType::New();

具體代碼實現：
（1）OpenCV由IplImage對BMP圖像灰度值反轉

IplImage* invertIntensity(IplImage* image)
{
    for(int y = 0; y < image->height; y++)
        for(int x = 0; x < image->widthStep; x++)
        {
            //widthStep = width * 3, 對應RGB3個分量
            uchar temp = image->imageData[y * image->widthStep + x];
            if(temp == 0)
                image->imageData[y * image->widthStep + x] = 255;
            else
                image->imageData[y * image->widthStep + x] = 0;
        }

        return image;
}

(2)QT由QImage對BMP圖像灰度值反轉

//qimage爲自定義類名
void qimage:: invertIntensity()
{
    QImage* img = new QImage();
    QImage* outImg;
    img->load("D:/openCV/Project/readImage/data/binary.bmp");
    QGraphicsScene* sceneImg = new QGraphicsScene();
    sceneImg->addPixmap(QPixmap::fromImage(*img));
    ui->originalImg->setScene(sceneImg);
    ui->originalImg->show();

    //invert intensity
    unsigned char* data = img->bits();//獲取圖像像素字節數據的首地址
    int height = img->height();
    int width = img->width();
    int bytesPerLine = img->bytesPerLine();//width * 4, 與OpenCV中區分
    unsigned char* outdata = new unsigned char[bytesPerLine * height];

    for(int y = 0; y < height; y++)
        for(int x = 0; x < width; x++)
        {
            if(data[y * bytesPerLine + x * 4] == 0)
            {
                outdata[y * bytesPerLine + x * 4 ] = 255;//B
                outdata[y * bytesPerLine + x * 4 + 1] = 255;//G
                outdata[y * bytesPerLine + x * 4 + 2] = 255;//R
                //A, 該分量保持不變
                outdata[y * bytesPerLine + x * 4 + 3] = data[y * bytesPerLine + x * 4 + 3];
            }
            else
            {
                outdata[y * bytesPerLine + x * 4 ] = 0;
                outdata[y * bytesPerLine + x * 4 + 1] = 0;
                outdata[y * bytesPerLine + x * 4 + 2] = 0;
                outdata[y * bytesPerLine + x * 4 + 3] = data[y * bytesPerLine + x * 4 + 3];
            }
        }

       //QImage::Format_RGB32, 有多種格式，選擇合適的格式很重要
       outImg = new QImage(outdata,width,height,bytesPerLine,QImage::Format_RGB32);
        //初始圖，結果圖要對應不同的 QGraphicsScene*
        QGraphicsScene* sceneOutImg = new QGraphicsScene();
        sceneOutImg->addPixmap(QPixmap::fromImage(*outImg));
        ui->resultImg->setScene(sceneOutImg);
        ui->resultImg->show(); 

        delete[]outImg;
}

(3)ITK由reader指針對BMP圖像灰度值反轉

    reader->SetFileName( argv[1] );
    reader->Update();
    inputImage = reader->GetOutput();

    //獲取圖像尺寸
    InputImageType::SizeType imgSize = inputImage->GetLargestPossibleRegion().GetSize();

    //直接訪問bmp圖像內存, 不考慮RGB三個分量
    InputImageType::IndexType index;
    for(int y = 0; y < imgSize[1]; y++)
        for(int x = 0; x < imgSize[0]; x++)
        {
            index[0] = x;
            index[1] = y;
            unsigned char temp;
            temp = inputImage->GetPixel(index);
            if(temp == 0)
                inputImage->SetPixel(index, 255);
            else
                inputImage->SetPixel(index, 0);
        }

讀入BMP圖像，經過灰度值反轉後，結果基於QT顯示，左圖爲原圖，右圖爲結果圖：