Javier Goizueta
7ac3784f32
This value would ideally be adjusted to prevent the grid size of the overview used being greater that one pixel. So, this should be the larger dimension of the map window in pixels.
89 lines
3.1 KiB
JavaScript
89 lines
3.1 KiB
JavaScript
var _ = require('underscore');
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var BaseWidget = require('../base');
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function BaseOverviewsDataview(query, queryOptions, BaseDataview, queryRewriter, queryRewriteData, options) {
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this.BaseDataview = BaseDataview;
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this.query = query;
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this.queryOptions = queryOptions;
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this.queryRewriter = queryRewriter;
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this.queryRewriteData = queryRewriteData;
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this.options = options;
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this.baseDataview = new this.BaseDataview(this.query, this.queryOptions);
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}
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module.exports = BaseOverviewsDataview;
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BaseOverviewsDataview.prototype = new BaseWidget();
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BaseOverviewsDataview.prototype.constructor = BaseOverviewsDataview;
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// TODO: parameterized these settings
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var SETTINGS = {
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// use overviews as a default fallback strategy
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defaultOverviews: false,
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// minimum ratio of bounding box size to grid size
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// (this would ideally be based on the viewport size in pixels)
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zoomLevelFactor: 1024.0
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};
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// Compute zoom level so that the the resolution grid size of the
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// selected overview is smaller (zoomLevelFactor times smaller at least)
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// than the bounding box size.
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BaseOverviewsDataview.prototype.zoomLevelForBbox = function(bbox) {
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var pxPerTile = 256.0;
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var earthWidth = 360.0;
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// TODO: now we assume overviews are computed for 1-pixel tolerance;
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// should use extended overviews metadata to compute this properly.
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if ( bbox ) {
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var bboxValues = _.map(bbox.split(','), function(v) { return +v; });
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var w = Math.abs(bboxValues[2]-bboxValues[0]);
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var h = Math.abs(bboxValues[3]-bboxValues[1]);
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var maxDim = Math.min(w, h);
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// Find minimum suitable z
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// note that the QueryRewirter will use the minimum level overview
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// of level >= z if it exists, and otherwise the base table
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var z = Math.ceil(-Math.log(maxDim*pxPerTile/earthWidth/SETTINGS.zoomLevelFactor)/Math.log(2.0));
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return Math.max(z, 0);
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}
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return 0;
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};
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BaseOverviewsDataview.prototype.rewrittenQuery = function(query) {
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var zoom_level = this.zoomLevelForBbox(this.options.bbox);
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return this.queryRewriter.query(query, this.queryRewriteData, { zoom_level: zoom_level });
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};
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// Default behaviour
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BaseOverviewsDataview.prototype.defaultSql = function(psql, filters, override, callback) {
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var query = this.query;
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var dataview = this.baseDataview;
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if ( SETTINGS.defaultOverviews ) {
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query = this.rewrittenQuery(query);
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dataview = new this.BaseDataview(query, this.queryOptions);
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}
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return dataview.sql(psql, filters, override, callback);
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};
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// default implementation that can be override in derived classes:
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BaseOverviewsDataview.prototype.sql = function(psql, filters, override, callback) {
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return this.defaultSql(psql, filters, override, callback);
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};
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BaseOverviewsDataview.prototype.search = function(psql, userQuery, callback) {
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return this.baseDataview.search(psql, userQuery, callback);
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};
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BaseOverviewsDataview.prototype.format = function(result) {
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return this.baseDataview.format(result);
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};
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BaseOverviewsDataview.prototype.getType = function() {
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return this.baseDataview.getType();
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};
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BaseOverviewsDataview.prototype.toString = function() {
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return this.baseDataview.toString();
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};
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