calculating histogramm

[bitbay]

My next try was to add a @Manual declaration to the legacy cv.mGet function, which is an INLINE declaration in opencv-src/modules/core/include/opencv2/core/types_c.h as:

CV_INLINE double cvmGet( const CvMat* mat, int row, int col )
{
int type;

type = CV_MAT_TYPE(mat->type);
assert( (unsigned)row < (unsigned)mat->rows &&
(unsigned)col < (unsigned)mat->cols );

if( type == CV_32FC1 )
return ((float_)(mat->data.ptr + (size_t)mat->step_row))[col];
else
{
assert( type == CV_64FC1 );
return ((double_)(mat->data.ptr + (size_t)mat->step_row))[col];
}
}

my try on the bea declaration to expose the method in opencv_manual.cpp:

v8::Handlev8::Value JOpenCV::mGet(const v8::Arguments& args) {
METHOD_BEGIN(1);
//float mGet(const Mat* mat, int row, int col)
//TODO: Enter code here
cv::Mat* mat = bea::Convertcv::Mat*::FromJS(args[0], 0);
int row = bea::Convert::FromJS(args[1], 1);
int col = bea::Convert::FromJS(args[2], 2);
THROW_IF_NOT(row > 0, "Invalid row value");
THROW_IF_NOT(col > 0, "Invalid col value");

// float or double?

float* ptr = (float_)(mat->data + (size_t)mat->step_row);
// i get negative values too -> obviously wrong pointer/bad value for color...
float result = ptr[col];
return bea::Convert::ToJS(result);
METHOD_END();
}

(as You can see i'm still no good at all in CPP / v8)

What values use this v8 port for storing colors? Floats, doubles, uchars?

[codeboost]

cvmGet seems to be an older C-Style interface to opencv.
If I'm not mistaken, you should use Mat::at to access individual elements of a matrix.

I'm currently working on calcHist and all the required dependencies, including the Mat::at() function and I should soon have an update ready.

[codeboost]

Just commited a new version of opencv-node, which includes cv.calcHist implementation and an example in the scripts directory. Let me know if that works for you