Merge pull request #299 from rdvincent/rdv-zoom

Several changes to improve zooming behaviour.

Author: natacha-beck

examples/volume-viewer-demo.js

@@ -285,6 +285,13 @@ $(function() {
       });
     });
 
+    $(document).keypress(function(e) {
+      if (e.keyCode === 114) {
+        // Reset displays if user presses 'r' key.
+        viewer.resetDisplays();
+        viewer.redrawVolumes();
+      }
+    });
     //////////////////////////////////
     // Per volume UI hooks go in here.
     //////////////////////////////////

src/brainbrowser/volume-viewer/lib/panel.js

@@ -295,9 +295,10 @@
       * ```
       */
       reset: function() {
-        panel.zoom = 1;
+        panel.zoom = panel.default_zoom;
         panel.image_center.x = panel.canvas.width / 2;
         panel.image_center.y = panel.canvas.height / 2;
+        panel.updated = true;
       },
 
       /**
@@ -496,7 +497,10 @@
     }
 
     if (panel.volume) {
-      setSlice(panel, panel.volume.slice(panel.axis));
+      var volume = panel.volume;
+      setSlice(panel, volume.slice(panel.axis));
+      panel.default_zoom = volume.getPreferredZoom(panel.canvas.width, panel.canvas.height);
+      panel.zoom = panel.default_zoom;
     }
 
     return panel;
@@ -517,7 +521,7 @@
     var context = panel.context;
     var cursor = panel.getCursorPosition();
     var zoom = panel.zoom;
-    var length = 8 * zoom;
+    var length = 8 * (zoom / panel.default_zoom);
     var x, y, space;
     var distance;
     var dx, dy;
@@ -528,7 +532,7 @@
     context.strokeStyle = color;
     context.fillStyle = color;
 
-    space = zoom;
+    space = 1;
     x = cursor.x;
     y = cursor.y;
 

src/brainbrowser/volume-viewer/modules/loading.js

@@ -646,7 +646,7 @@ BrainBrowser.VolumeViewer.modules.loading = function(viewer) {
 
           last_touch_distance = null;
         }
-        
+
         canvas.addEventListener("mousedown", function(event) {
           event.preventDefault();
 
@@ -696,7 +696,8 @@ BrainBrowser.VolumeViewer.modules.loading = function(viewer) {
         }
 
         function zoom(delta) {
-          panel.zoom = Math.max(panel.zoom + delta * 0.05, 0.05);
+          panel.zoom *= (delta < 0) ? 1/1.05 : 1.05;
+          panel.zoom = Math.max(panel.zoom, 0.25);
           panel.updateVolumePosition();
           panel.updateSlice();
 

src/brainbrowser/volume-viewer/volume-loaders/minc.js

@@ -372,6 +372,21 @@
       },
       getVoxelMax: function() {
         return volume.header.voxel_max;
+      },
+      /* given a width and height (from the panel), this function returns the "best"
+       * single zoom level that will guarantee that the image fits exactly into the
+       * current panel.
+       */
+      getPreferredZoom: function(width, height) {
+        var header = volume.header;
+        var x_fov = header.xspace.space_length * Math.abs(header.xspace.step);
+        var y_fov = header.yspace.space_length * Math.abs(header.yspace.step);
+        var z_fov = header.zspace.space_length * Math.abs(header.xspace.step);
+        var xw = width / x_fov;
+        var yw = width / y_fov;
+        var yh = height / y_fov;
+        var zh = height / z_fov;
+        return Math.min(yw, xw, zh, yh);
       }
     };
     return volume;