Нет простой функции для доступа к подпикселю, но я могу предложить несколько вариантов:
cv::Vec3b getColorSubpix(const cv::Mat& img, cv::Point2f pt)
{
cv::Mat patch;
cv::getRectSubPix(img, cv::Size(1,1), pt, patch);
return patch.at(0,0);
}
cv::Vec3b getColorSubpix(const cv::Mat& img, cv::Point2f pt)
{
cv::Mat patch;
cv::remap(img, patch, cv::Mat(1, 1, CV_32FC2, &pt), cv::noArray(),
cv::INTER_LINEAR, cv::BORDER_REFLECT_101);
return patch.at(0,0);
}
cv::Vec3b getColorSubpix(const cv::Mat& img, cv::Point2f pt)
{
assert(!img.empty());
assert(img.channels() == 3);
int x = (int)pt.x;
int y = (int)pt.y;
int x0 = cv::borderInterpolate(x, img.cols, cv::BORDER_REFLECT_101);
int x1 = cv::borderInterpolate(x+1, img.cols, cv::BORDER_REFLECT_101);
int y0 = cv::borderInterpolate(y, img.rows, cv::BORDER_REFLECT_101);
int y1 = cv::borderInterpolate(y+1, img.rows, cv::BORDER_REFLECT_101);
float a = pt.x - (float)x;
float c = pt.y - (float)y;
uchar b = (uchar)cvRound((img.at(y0, x0)[0] * (1.f - a) + img.at(y0, x1)[0] * a) * (1.f - c)
+ (img.at(y1, x0)[0] * (1.f - a) + img.at(y1, x1)[0] * a) * c);
uchar g = (uchar)cvRound((img.at(y0, x0)[1] * (1.f - a) + img.at(y0, x1)[1] * a) * (1.f - c)
+ (img.at(y1, x0)[1] * (1.f - a) + img.at(y1, x1)[1] * a) * c);
uchar r = (uchar)cvRound((img.at(y0, x0)[2] * (1.f - a) + img.at(y0, x1)[2] * a) * (1.f - c)
+ (img.at(y1, x0)[2] * (1.f - a) + img.at(y1, x1)[2] * a) * c);
return cv::Vec3b(b, g, r);
}