openCV图像的读写操作

void QuickDemo::pixel_visit_demo(cv::Mat &image)
{
  int w = image.cols;
  int h = image.rows;
  int dim = image.channels();

  for (int row = 0; row < h; row++)
  {
	for (int col = 0; col < w; col++)
	{
	  if (dim == 1)//灰度图像
	  {
		int pv = image.at<uchar>(row,col);//像素是字节类型
		image.at<uchar>(row, col) = 255 - pv;
	  }
	  if (dim == 3)//彩色图像
	  {
		Vec3b bgr = image.at<Vec3b>(row, col);
		image.at<Vec3b>(row, col)[0] = 255 - bgr[0];
		image.at<Vec3b>(row, col)[1] = 255 - bgr[1];
		image.at<Vec3b>(row, col)[2] = 255 - bgr[2];
	  }
	}
  }

  for (int row = 0; row < h; row++)
  {
	uchar* current_row = image.ptr<uchar>(row);
	for (int col = 0; col < w; col++)
	{
	  if (dim == 1)//灰度图像
	  {
		int pv = *current_row;
		*current_row++ = 255 - *current_row;

	  }
	  if (dim == 3)//彩色图像
	  {
		*current_row++ = 255 - *current_row;
		*current_row++ = 255 - *current_row;
		*current_row++ = 255 - *current_row;
	  }
	}
  }

  imshow("像素读写", image);
}

一、数组下标

for (int row = 0; row < h; row++)
  {
	for (int col = 0; col < w; col++)
	{
	  if (dim == 1)//灰度图像
	  {
		int pv = image.at<uchar>(row,col);//像素是字节类型
		image.at<uchar>(row, col) = 255 - pv;
	  }
	  if (dim == 3)//彩色图像
	  {
		Vec3b bgr = image.at<Vec3b>(row, col);
		image.at<Vec3b>(row, col)[0] = 255 - bgr[0];
		image.at<Vec3b>(row, col)[1] = 255 - bgr[1];
		image.at<Vec3b>(row, col)[2] = 255 - bgr[2];
	  }
	}
  }

• 如果图像是灰度图像（通道数为1），则使用.at(row, col)来访问像素值，并将像素值取反后写回图像
• 如果图像是彩色图像（通道数为3），则使用.at(row, col)来访问像素值。将每个通道的像素值取反后写回图像

二、指针

for (int row = 0; row < h; row++)
  {
	uchar* current_row = image.ptr<uchar>(row);
	for (int col = 0; col < w; col++)
	{
	  if (dim == 1)//灰度图像
	  {
		int pv = *current_row;
		*current_row++ = 255 - *current_row;

	  }
	  if (dim == 3)//彩色图像
	  {
		*current_row++ = 255 - *current_row;
		*current_row++ = 255 - *current_row;
		*current_row++ = 255 - *current_row;
	  }
	}
  }

• 对于灰度图像，使用指针current_row指向当前行的数据指针，然后通过*current_row++的方式逐个访问像素值，并将像素值取反后写回图像
• 对于彩色图像，同样使用指针current_row指向当前行的数据指针，然后通过*current_row++的方式逐个访问每个通道的像素值，并将像素值取反后写回图像

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