[grits] Add support for Mercator projections in tiles
- From: Andy Spencer <andys src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [grits] Add support for Mercator projections in tiles
- Date: Thu, 16 Feb 2012 23:17:03 +0000 (UTC)
commit 04171adb63df1084005faadd94419a64db072596
Author: Andy Spencer <andy753421 gmail com>
Date: Sat Jan 21 04:16:25 2012 +0000
Add support for Mercator projections in tiles
This split tiles in the correct
src/data/grits-tms.c | 62 +++++++----------------------
src/grits-viewer.h | 6 +-
src/objects/grits-tile.c | 96 +++++++++++++++++++++++++++++++---------------
src/objects/grits-tile.h | 3 +
4 files changed, 86 insertions(+), 81 deletions(-)
---
diff --git a/src/data/grits-tms.c b/src/data/grits-tms.c
index cfe84f5..48f5b0c 100644
--- a/src/data/grits-tms.c
+++ b/src/data/grits-tms.c
@@ -25,63 +25,31 @@
static gchar *_make_uri(GritsTms *tms, GritsTile *tile)
{
-
-#if 0
- /* This doesn't make any sense.. */
- gdouble lon_rad = deg2rad(tile->edge.n + tile->edge.s)/2;
- gdouble lat_rad = deg2rad(tile->edge.e + tile->edge.w)/2;
- g_message("%lf,%lf", lat_rad, lon_rad);
-
- /* Reproject the coordinates to the Mercator projection: */
- gdouble x = lon_rad;
- gdouble y = log(tan(lat_rad) + 1.0/cos(lat_rad));
-
- /* Transform range of x and y to 0 - 1 and shift origin to top left */
- x = (1.0 + (x / G_PI)) / 2.0;
- y = (1.0 - (y / G_PI)) / 2.0;
-
- /* Calculate the number of tiles across the map, n, using 2^zoom */
- gint zoom = 0;
- for (GritsTile *tmp = tile->parent; tmp; tmp = tmp->parent)
- zoom++;
- gint n = pow(2, zoom);
-
- /* Multiply x and y by n. Round results down to give tilex and tiley. */
- gint xtile = x * n;
- gint ytile = y * n;
-
- g_message("xy=%f,%f zoom=%d n=%d xy_tiles=%d,%d",
- x, y, zoom, n, xtile, ytile);
-#endif
-
-#if 1
- /* This is broken */
gint zoom = 0;
for (GritsTile *tmp = tile->parent; tmp; tmp = tmp->parent)
zoom++;
gint breath = pow(2,zoom);
- gdouble lon_pos = (tile->edge.e+tile->edge.w)/2 + 180;
- gdouble lat_pos = -(tile->edge.n+tile->edge.s)/2 + 90 - 4.9489;
+ gdouble lat_top = asinh(tan(deg2rad(tile->edge.n)));
+ gdouble lat_bot = asinh(tan(deg2rad(tile->edge.s)));
- gdouble lon_total = 360;
- gdouble lat_total = 85.0511*2;
+ gdouble lat_mid = (lat_top + lat_bot)/2.0;
+ gdouble lon_mid = (tile->edge.e + tile->edge.w)/2.0;
- gdouble lon_pct = lon_pos / lon_total;
- gdouble lat_pct = lat_pos / lat_total;
+ gdouble lat_pos = 1.0 - (lat_mid + G_PI) / (2.0*G_PI);
+ gdouble lon_pos = (lon_mid + 180.0) / 360.0;
- gint xtile = lon_pct * breath;
- gint ytile = lat_pct * breath;
+ gint xtile = lon_pos * breath;
+ gint ytile = lat_pos * breath;
- //g_message("bbok=%f,%f,%f,%f",
+ //g_message("tile=%f,%f,%f,%f t=%p p=%p",
// tile->edge.n, tile->edge.s,
- // tile->edge.e, tile->edge.w);
- //g_message("pos=%f,%f total=%f,%f pct=%f,%f tile=%d,%d",
- // lon_pos, lat_pos,
- // lon_total, lat_total,
- // lon_pct, lat_pct,
- // xtile, ytile);
-#endif
+ // tile->edge.e, tile->edge.w, tile, tile->parent);
+ //g_message("top=%lf->%lf bot=%lf->%lf pos=%lf,%lf tile=%d,%d,%d",
+ // tile->edge.n, lat_top,
+ // tile->edge.s, lat_bot,
+ // lat_pos, lon_pos,
+ // zoom, xtile, ytile);
// http://tile.openstreetmap.org/<zoom>/<xtile>/<ytile>.png
return g_strdup_printf("%s/%d/%d/%d.%s",
diff --git a/src/grits-viewer.h b/src/grits-viewer.h
index b7ff216..15d9d70 100644
--- a/src/grits-viewer.h
+++ b/src/grits-viewer.h
@@ -39,10 +39,10 @@
#include <glib-object.h>
/* Projections */
-enum {
+typedef enum {
+ GRITS_PROJ_LATLON,
GRITS_PROJ_MERCATOR,
- GRITS_PROJ_EQUIRECTANGULAR,
-} GritsProjection;
+} GritsProj;
/* Rendering levels */
/**
diff --git a/src/objects/grits-tile.c b/src/objects/grits-tile.c
index c8326da..68e71cc 100644
--- a/src/objects/grits-tile.c
+++ b/src/objects/grits-tile.c
@@ -33,6 +33,7 @@
*/
#include <config.h>
+#include <math.h>
#include "gtkgl.h"
#include "grits-tile.h"
@@ -61,6 +62,8 @@ GritsTile *grits_tile_new(GritsTile *parent,
tile->atime = time(NULL);
grits_bounds_set_bounds(&tile->coords, 0, 1, 1, 0);
grits_bounds_set_bounds(&tile->edge, n, s, e, w);
+ if (parent)
+ tile->proj = parent->proj;
return tile;
}
@@ -133,6 +136,43 @@ static gboolean _grits_tile_precise(GritsPoint *eye, GritsBounds *bounds,
tile_res < view_res;
}
+static void _grits_tile_split_latlon(GritsTile *tile)
+{
+ const gdouble rows = G_N_ELEMENTS(tile->children);
+ const gdouble cols = G_N_ELEMENTS(tile->children[0]);
+ const gdouble lat_dist = tile->edge.n - tile->edge.s;
+ const gdouble lon_dist = tile->edge.e - tile->edge.w;
+ const gdouble lat_step = lat_dist / rows;
+ const gdouble lon_step = lon_dist / cols;
+
+ int row, col;
+ grits_tile_foreach_index(tile, row, col)
+ tile->children[row][col] = grits_tile_new(tile,
+ tile->edge.n - lat_step*(row+0), // north
+ tile->edge.n - lat_step*(row+1), // south
+ tile->edge.w + lon_step*(col+1), // east
+ tile->edge.w + lon_step*(col+0)); // west
+}
+
+static void _grits_tile_split_mercator(GritsTile *tile)
+{
+ GritsTile *child = NULL;
+ GritsBounds tmp = tile->edge;
+
+ /* Project */
+ tile->edge.n = asinh(tan(deg2rad(tile->edge.n)));
+ tile->edge.s = asinh(tan(deg2rad(tile->edge.s)));
+
+ _grits_tile_split_latlon(tile);
+
+ /* Convert back to lat-lon */
+ tile->edge = tmp;
+ grits_tile_foreach(tile, child) {
+ child->edge.n = rad2deg(atan(sinh(child->edge.n)));
+ child->edge.s = rad2deg(atan(sinh(child->edge.s)));
+ }
+}
+
/**
* grits_tile_update:
* @root: the root tile to split
@@ -149,43 +189,37 @@ static gboolean _grits_tile_precise(GritsPoint *eye, GritsBounds *bounds,
* the tile is recursively subdivided until a sufficient resolution is
* achieved.
*/
-void grits_tile_update(GritsTile *root, GritsPoint *eye,
+void grits_tile_update(GritsTile *tile, GritsPoint *eye,
gdouble res, gint width, gint height,
GritsTileLoadFunc load_func, gpointer user_data)
{
- root->atime = time(NULL);
//g_debug("GritsTile: update - %p->atime = %u",
- // root, (guint)root->atime);
- const gdouble rows = G_N_ELEMENTS(root->children);
- const gdouble cols = G_N_ELEMENTS(root->children[0]);
- const gdouble lat_dist = root->edge.n - root->edge.s;
- const gdouble lon_dist = root->edge.e - root->edge.w;
- const gdouble lat_step = lat_dist / rows;
- const gdouble lon_step = lon_dist / cols;
- int row, col;
- grits_tile_foreach_index(root, row, col) {
- GritsBounds edge;
- edge.n = root->edge.n-(lat_step*(row+0));
- edge.s = root->edge.n-(lat_step*(row+1));
- edge.e = root->edge.w+(lon_step*(col+1));
- edge.w = root->edge.w+(lon_step*(col+0));
-
- GritsTile **child = &root->children[row][col];
- if (!_grits_tile_precise(eye, &edge, res,
- width/cols, height/rows)) {
- if (!*child) {
- *child = grits_tile_new(root, edge.n, edge.s,
- edge.e, edge.w);
- load_func(*child, user_data);
- }
- grits_tile_update(*child, eye,
- res, width, height,
- load_func, user_data);
- GRITS_OBJECT(*child)->hidden = FALSE;
- } else if (*child) {
- GRITS_OBJECT(*child)->hidden = TRUE;
+ // tile, (guint)tile->atime);
+
+ if (tile == NULL)
+ return;
+
+ GRITS_OBJECT(tile)->hidden = TRUE;
+ if (_grits_tile_precise(eye, &tile->edge, res, width, height))
+ return;
+ tile->atime = time(NULL);
+ GRITS_OBJECT(tile)->hidden = FALSE;
+
+ if (!tile->data)
+ load_func(tile, user_data);
+
+ if (!tile->children[0][0]) {
+ switch (tile->proj) {
+ case GRITS_PROJ_LATLON: _grits_tile_split_latlon(tile); break;
+ case GRITS_PROJ_MERCATOR: _grits_tile_split_mercator(tile); break;
}
}
+
+ GritsTile *child;
+ grits_tile_foreach(tile, child)
+ grits_tile_update(child, eye, res, width, height,
+ load_func, user_data);
+
}
/**
diff --git a/src/objects/grits-tile.h b/src/objects/grits-tile.h
index 309f4bc..f2b706f 100644
--- a/src/objects/grits-tile.h
+++ b/src/objects/grits-tile.h
@@ -53,6 +53,9 @@ struct _GritsTile {
/* Last access time (for garbage collection) */
time_t atime;
+
+ /* Projection used by tile data */
+ GritsProj proj;
};
struct _GritsTileClass {
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