I am trying to use OpenVX Histogram (as per Spec 1.1) and little puzzled in the usage part. My understanding is like this (Please correct me):
vx_size numBins = 10;
vx_uint32 offset = 10;
vx_uint32 range = 256;
// Create Object
vx_distribution vx_dist = vxCreateDistribution (Context, numBins, offset,
range);
// Create Node
vx_status status = vxHistogramNode (context, img, vx_dist);
Spec says that vxHistogramNode() takes vx_distribution as [out], does that means vxHistogramNode() creates object internally? If the answer is 'Yes' than how would i pass numBins, Offset and range of my choice?
Also. how can i access the output of histogram result?
The out means that the node will write the result to provided data object. So you pass your object to the node, run the graph and then read the result:
// Create Object
vx_size numBins = 10;
vx_uint32 offset = 10;
vx_uint32 range = 256;
vx_distribution vx_dist = vxCreateDistribution (Context, numBins, offset, range);
vx_graph graph = vxCreateGraph(context);
vxHistogramNode(graph, img, vx_dist);
vxVerifyGraph(graph);
vxProcessGraph(graph);
// Read the data
vx_map_id map_id;
vx_int32 *ptr;
vxMapDistribution(vx_dist, &map_id, (void **)&ptr, VX_READ_ONLY, VX_MEMORY_TYPE_HOST, 0);
// use ptr, like ptr[0]
vxUnmapDistribution(vx_dist, map_id);
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