From 326d9046df71e07cb79d975073c8d729d5748a93 Mon Sep 17 00:00:00 2001
From: David Manthey <david.manthey@kitware.com>
Date: Tue, 30 Apr 2019 15:08:35 -0400
Subject: [PATCH] Improve tile overlap.

The common tile server with overlapping tiles is deep zoom.  Tiles in
the center of the image have overlap on all four sides, but tiles at the
edges don't overlap past the conceptual image space.  We properly
handled the right and bottom, but the top and left edges were expecting
tiles that were larger than deep zoom was providing.  For instance, a
256x256 tile with an overlap of 1 produces a 258x258 tile in the center,
but a 257x257 tile at the upper left and a 257x258 else on the left
edge.  This handles those properly.

The deepzoom example also maintains query parameters, making it easier
to modify for testing.
---
 examples/deepzoom/main.js |  7 ++++---
 src/imageTile.js          |  2 +-
 src/tile.js               | 10 ++++++++--
 tests/cases/tile.js       |  4 ++--
 4 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/examples/deepzoom/main.js b/examples/deepzoom/main.js
index 322809426f..b2e5b5beef 100644
--- a/examples/deepzoom/main.js
+++ b/examples/deepzoom/main.js
@@ -11,8 +11,8 @@ var DeepZoom = function (arg) {
     return geo.imageTile({
       index: index,
       size: {
-        x: this._options.tileWidth + this._options.tileOverlap.x * 2,
-        y: this._options.tileHeight + this._options.tileOverlap.y * 2
+        x: this._options.tileWidth,
+        y: this._options.tileHeight
       },
       queue: this._queue,
       url: this._options.url(source || index),
@@ -30,6 +30,7 @@ var query = utils.getQuery();
 // You can specify a different Deep Zoom image via ?url=(url to dzi or xml)
 var dzi_url = query.url || 'https://mars.nasa.gov/msl/multimedia/deepzoom/images/PIA19818/dzc_output.xml';
 var dzi_base = dzi_url.split('.').slice(0, -1).join('.') + '_files';
+var dzi_query = dzi_url.indexOf('?') >= 0 ? dzi_url.substr(dzi_url.indexOf('?')) : '';
 
 // Read the Deep Zoom image information.
 $.get(dzi_url).then(function (dzi_info) {
@@ -60,7 +61,7 @@ $.get(dzi_url).then(function (dzi_info) {
       features: query.renderer ? undefined : ['quad.imageFixedScale'],
       // Specify a custom url for tiles.  Deep Zoom offsets the level by 8
       url: function (index) {
-        return dzi_base + '/' + (index.level + 8) + '/' + index.x + '_' + index.y + '.' + format;
+        return dzi_base + '/' + (index.level + 8) + '/' + index.x + '_' + index.y + '.' + format + dzi_query;
       },
       // Specify the tile overlap
       tileOverlap: {
diff --git a/src/imageTile.js b/src/imageTile.js
index 37e87b2303..eeed7a45a4 100644
--- a/src/imageTile.js
+++ b/src/imageTile.js
@@ -64,7 +64,7 @@ var imageTile = function (spec) {
   this.fetch = function () {
     var defer;
     if (!this._image) {
-      this._image = new Image(this.size.x, this.size.y);
+      this._image = new Image(this.right - this.left, this.bottom - this.top);
       // Only set the crossOrigin parameter if this is going across origins.
       if (this._cors && this._url.indexOf(':') >= 0 &&
           this._url.indexOf('/') === this._url.indexOf(':') + 1) {
diff --git a/src/tile.js b/src/tile.js
index 1f5fc909fc..229bdaef15 100644
--- a/src/tile.js
+++ b/src/tile.js
@@ -165,6 +165,12 @@ var tile = function (spec) {
     right = left + this.size.x + this.overlap.x * 2;
     top = this.size.y * (this.index.y - index.y) - this.overlap.y - shift.y;
     bottom = top + this.size.y + this.overlap.y * 2;
+    if (this.overlap.x && this.index.x === index.x) {
+      left += this.overlap.x;
+    }
+    if (this.overlap.y && this.index.y === index.y) {
+      top += this.overlap.y;
+    }
     return {
       left: left,
       right: right,
@@ -191,7 +197,7 @@ var tile = function (spec) {
    */
   Object.defineProperty(this, 'top', {
     get: function () {
-      return this.size.y * this.index.y - this.overlap.y;
+      return this.size.y * this.index.y - (this.index.y ? this.overlap.y : 0);
     }
   });
 
@@ -202,7 +208,7 @@ var tile = function (spec) {
    */
   Object.defineProperty(this, 'left', {
     get: function () {
-      return this.size.x * this.index.x - this.overlap.x;
+      return this.size.x * this.index.x - (this.index.x ? this.overlap.x : 0);
     }
   });
 
diff --git a/tests/cases/tile.js b/tests/cases/tile.js
index 0a967c8618..d01562d616 100644
--- a/tests/cases/tile.js
+++ b/tests/cases/tile.js
@@ -96,8 +96,8 @@ describe('geo.tile', function () {
       });
 
       expect(t.bottom).toEqual(12);
-      expect(t.left).toEqual(-1);
-      expect(t.top).toEqual(-2);
+      expect(t.left).toEqual(0);
+      expect(t.top).toEqual(0);
       expect(t.right).toEqual(11);
 
       t = geo.tile({