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Fixed opponent space color conversion

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This commit is contained in:
Andrey Kamaev 2012-07-03 11:01:56 +00:00
parent cfc593eb0d
commit aa4cad80a0
1 changed files with 10 additions and 43 deletions
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53
modules/features2d/src/descriptors.cpp
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@ -122,57 +122,24 @@ static void convertBGRImageToOpponentColorSpace( const Mat& bgrImage, vector<Mat
if( bgrImage.type() != CV_8UC3 ) if( bgrImage.type() != CV_8UC3 )
CV_Error( CV_StsBadArg, "input image must be an BGR image of type CV_8UC3" ); CV_Error( CV_StsBadArg, "input image must be an BGR image of type CV_8UC3" );
// Split image into RGB to allow conversion to Opponent Color Space.
vector<Mat> bgrChannels(3);
split( bgrImage, bgrChannels );
// Prepare opponent color space storage matrices. // Prepare opponent color space storage matrices.
opponentChannels.resize( 3 ); opponentChannels.resize( 3 );
opponentChannels[0] = cv::Mat(bgrImage.size(), CV_8UC1); // R-G RED-GREEN opponentChannels[0] = cv::Mat(bgrImage.size(), CV_8UC1); // R-G RED-GREEN
opponentChannels[1] = cv::Mat(bgrImage.size(), CV_8UC1); // R+G-2B YELLOW-BLUE opponentChannels[1] = cv::Mat(bgrImage.size(), CV_8UC1); // R+G-2B YELLOW-BLUE
opponentChannels[2] = cv::Mat(bgrImage.size(), CV_8UC1); // R+G+B opponentChannels[2] = cv::Mat(bgrImage.size(), CV_8UC1); // R+G+B
// Calculate the channels of the opponent color space for(int y = 0; y < bgrImage.rows; ++y)
{ for(int x = 0; x < bgrImage.cols; ++x)
// (R - G)/sqrt(2), but converted to the destination data type
MatConstIterator_<signed char> rIt = bgrChannels[2].begin<signed char>();
MatConstIterator_<signed char> gIt = bgrChannels[1].begin<signed char>();
MatIterator_<unsigned char> dstIt = opponentChannels[0].begin<unsigned char>();
for( ; dstIt != opponentChannels[0].end<unsigned char>(); ++rIt, ++gIt, ++dstIt )
{ {
float value = 0.5f * (static_cast<int>(*gIt) - Vec3b v = bgrImage.at<Vec3b>(y, x);
static_cast<int>(*rIt) + 255); uchar& b = v[0];
(*dstIt) = static_cast<unsigned char>(value + 0.5f); uchar& g = v[1];
uchar& r = v[2];
opponentChannels[0].at<uchar>(y, x) = saturate_cast<uchar>(0.5f * (255 + g - r)); // (R - G)/sqrt(2), but converted to the destination data type
opponentChannels[1].at<uchar>(y, x) = saturate_cast<uchar>(0.25f * (510 + r + g - 2*b)); // (R + G - 2B)/sqrt(6), but converted to the destination data type
opponentChannels[2].at<uchar>(y, x) = saturate_cast<uchar>(1.f/3.f * (r + g + b)); // (R + G + B)/sqrt(3), but converted to the destination data type
} }
}
{
// (R + G - 2B)/sqrt(6), but converted to the destination data type
MatConstIterator_<signed char> rIt = bgrChannels[2].begin<signed char>();
MatConstIterator_<signed char> gIt = bgrChannels[1].begin<signed char>();
MatConstIterator_<signed char> bIt = bgrChannels[0].begin<signed char>();
MatIterator_<unsigned char> dstIt = opponentChannels[1].begin<unsigned char>();
for( ; dstIt != opponentChannels[1].end<unsigned char>(); ++rIt, ++gIt, ++bIt, ++dstIt )
{
float value = 0.25f * (static_cast<int>(*rIt) + static_cast<int>(*gIt) -
2*static_cast<int>(*bIt) + 510);
(*dstIt) = static_cast<unsigned char>(value + 0.5f);
}
}
{
// (R + G + B)/sqrt(3), but converted to the destination data type
MatConstIterator_<signed char> rIt = bgrChannels[2].begin<signed char>();
MatConstIterator_<signed char> gIt = bgrChannels[1].begin<signed char>();
MatConstIterator_<signed char> bIt = bgrChannels[0].begin<signed char>();
MatIterator_<unsigned char> dstIt = opponentChannels[2].begin<unsigned char>();
float factor = 1.f/3.f;
for( ; dstIt != opponentChannels[2].end<unsigned char>(); ++rIt, ++gIt, ++bIt, ++dstIt )
{
float value = factor * (static_cast<int>(*rIt) +
static_cast<int>(*gIt) +
static_cast<int>(*bIt));
(*dstIt) = static_cast<unsigned char>(value + 0.5f);
}
}
} }
struct KP_LessThan struct KP_LessThan