Method doOperation

src/IECoreImage/MedianCutSampler.cpp:219–281

ObjectPtr MedianCutSampler::doOperation( const CompoundObject * operands )
{
	ImagePrimitivePtr image = static_cast<ImagePrimitive *>( imageParameter()->getValue() )->copy();
	Box2i dataWindow = image->getDataWindow();

	// find the right channel
	const std::string &channelName = m_channelNameParameter->getTypedValue();
	FloatVectorDataPtr luminance = image->getChannel<float>( channelName );
	if( !luminance )
	{
		throw Exception( str( format( "No FloatVectorData channel named \"%s\"." ) % channelName ) );
	}

	// if the projection requires it, weight the luminances so they're less
	// important towards the poles of the sphere
	Projection projection = (Projection)m_projectionParameter->getNumericValue();
	if( projection==LatLong )
	{
		float radiansPerPixel = M_PI / (dataWindow.size().y + 1);
		float angle = ( M_PI - radiansPerPixel ) / 2.0f;

		float *p = &(luminance->writable()[0]);

		for( int y=dataWindow.min.y; y<=dataWindow.max.y; y++ )
		{
			float *pEnd = p + dataWindow.size().x + 1;
			float w = cosf( angle );
			while( p < pEnd )
			{
				*p *= w;
				p++;
			}
			angle -= radiansPerPixel;
		}

	}

	// make a summed area table for speed
	FloatVectorDataPtr summedLuminance = luminance;
	luminance = luminance->copy(); // we need this for the centroid computation

	SummedAreaOpPtr summedAreaOp = new SummedAreaOp();
	summedAreaOp->inputParameter()->setValue( image );
	summedAreaOp->copyParameter()->setTypedValue( false );
	summedAreaOp->channelNamesParameter()->getTypedValue().clear();
	summedAreaOp->channelNamesParameter()->getTypedValue().push_back( "Y" );
	summedAreaOp->operate();

	// do the median cut thing
	CompoundObjectPtr result = new CompoundObject;
	V2fVectorDataPtr centroids = new V2fVectorData;
	Box2iVectorDataPtr areas = new Box2iVectorData;
	result->members()["centroids"] = centroids;
	result->members()["areas"] = areas;

	dataWindow.max -= dataWindow.min;
	dataWindow.min -= dataWindow.min; // let's start indexing from 0 shall we?
	Array2D array( &(luminance->writable()[0]), extents[dataWindow.size().x+1][dataWindow.size().y+1], fortran_storage_order() );