CODEWITHSUNDEEP
c++opencv
Aaban
Aaban

Reputation: 1

Accessing negative pixel values OpenCV

IplImage* pRGBImg = cvLoadImage(input_file.c_str(), CV_LOAD_IMAGE_UNCHANGED); 
int width = pRGBImg->width; 
int height = pRGBImg->height;
int bpp = pRGBImg->nChannels; 
for (int i=0; i < width*height*bpp; i+=bpp) 
{
  if (!(i % (width*bpp))) // print empty line for better readability
      std::cout << std::endl;

  std::cout << std::dec << "R:" << (int) pRGBImg->imageData[i] <<  
                          " G:" << (int) pRGBImg->imageData[i+1] <<  
                          " B:" << (int) pRGBImg->imageData[i+2] << " "; 
}

this code is giving different pixel values what i got in matlab is in positive and open cv give value in negative.

Upvotes: 0

Views: 658

Answers (2)

murali kurapati
murali kurapati

Reputation: 1586

using uchar worked for me

std::cout << std::dec << "R:" << (uchar) pRGBImg->imageData[i] <<  
                         "G:" << (uchar) pRGBImg->imageData[i+1] <<  
                         "B:" << (uchar) pRGBImg->imageData[i+2] << " ";

Upvotes: 0

Karel Petranek
Karel Petranek

Reputation: 15154

You are probably converting a signed byte value to int which can give negative values. Try this code:

  std::cout << std::dec << "R:" << (unsigned int) pRGBImg->imageData[i] <<  
                          " G:" << (unsigned int) pRGBImg->imageData[i+1] <<  
                          " B:" << (unsigned int) pRGBImg->imageData[i+2] << " ";

Upvotes: 1

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