heatmap_datasource.cpp

/*
 * heatmap_datasource.cpp
 *
 *  Created on: Aug 8, 2011
 *      Author: stella
 */
#include "heatmap_datasource.hpp"
#include "density_mask.hpp"

#include "agg_gradient_lut.h"
#include "agg_rendering_buffer.h"
#include "agg_pixfmt_rgba.h"

using mapnik::datasource;
using mapnik::parameters;

DATASOURCE_PLUGIN(heatmap_datasource);

heatmap_datasource::heatmap_datasource(const mapnik::parameters& params, bool bind) :
		rasterizer_datasource(params, bind),
		desc_("heatmap", "utf-8")
{

}

heatmap_datasource::~heatmap_datasource()
{

}

std::string heatmap_datasource::name()
{
	return "heatmap";
}

mapnik::layer_descriptor heatmap_datasource::get_descriptor() const
{
	return desc_;
}

void heatmap_datasource::rasterize(rasterize_params& rp) const
{
	// Don't do anything if no source (shouldn't be possible but avoid segfault)
	if (!source()) {
		return;
	}

	density_mask mask(rp.image().width(), rp.image().height());

	// Setup geometry for plotting
	double	refx=rp.query().get_bbox().minx(),
			refy=rp.query().get_bbox().miny(),
			resx=rp.query().resolution().head,
			resy=rp.query().resolution().tail.head;
	int 	width=rp.image().width(),
			height=rp.image().height();

	// Open the source featureset
	mapnik::featureset_ptr fs=source()->features(rp.query());

	// Iterate over features
	while (mapnik::feature_ptr f=fs->next()) {
		mapnik::coord2d centroid(0,0);

		// Get average centroid of all geometries
		for (unsigned i=0; i<f->num_geometries(); i++) {
			const mapnik::geometry_type& g(f->get_geometry(i));

			double gx=0,gy=0;
			g.middle_point(&gx,&gy);
			centroid.x+=gx;
			centroid.y+=gy;
		}

		centroid/=f->num_geometries();

		// Plot the point
		int x=round((centroid.x - refx) * resx);
		int y=height - round((centroid.y - refy) * resy);

		if (x>=0 && y>=0 && x<width && y<height) {
			mask.set_sample(x, y, 1.0);
		} else {
			std::clog << "Sample out of range: (" << x << "," << y << ")" << std::endl;
		}
	}

	//mask.set_random_samples(250, true);
	mask.gaussian_blend(20, true);

	// Color gradient
	agg::gradient_lut<agg::color_interpolator<agg::rgba8> > color_lut;
	color_lut.remove_all();
	color_lut.add_color(0, agg::rgba8(0,0,128,0));
	color_lut.add_color(0.45, agg::rgba8(0,0,255,0));
	color_lut.add_color(0.55, agg::rgba8(0,255,255,0));
	color_lut.add_color(0.65, agg::rgba8(0,255,0,0));
	color_lut.add_color(0.95, agg::rgba8(139,139,0,0));
	color_lut.add_color(1.0, agg::rgba8(255,0,0,0));
	color_lut.build_lut();

	agg::gradient_lut<agg::color_interpolator<agg::gray8> > alpha_lut;
	alpha_lut.remove_all();
	alpha_lut.add_color(0, agg::gray8(0));
	alpha_lut.add_color(0.1, agg::gray8(150));
	alpha_lut.add_color(1.0, agg::gray8(255));
	alpha_lut.build_lut();

	// Setup agg rendering on top of output image buffer
	agg::rendering_buffer rbuf(rp.image().getBytes(),
			rp.image().width(),
			rp.image().height(),
			rp.image().width() * 4);
	agg::pixfmt_rgba32 pixf(rbuf);

	// Colorize the mask into the buffer
	mask.colorize(pixf, color_lut, alpha_lut);
}