6G-Reconstruction/VolumeDownscaling: moved to linear interpolation for the upscaling

Signed-off-by: Nicola Vigano <nicola.vigano@esrf.fr>

zUtil_Deformation/Gt6DReconstructionAlgorithmFactory.m

@@ -214,7 +214,7 @@ classdef Gt6DReconstructionAlgorithmFactory < handle
             end
 
             if (self.volume_downscaling > 1)
-                volume_size = round(volume_size / self.volume_downscaling);
+                volume_size = ceil(volume_size / self.volume_downscaling);
                 for ii = 1:num_geoms
                     geometries{ii}(:, 4:12) = geometries{ii}(:, 4:12) / self.volume_downscaling;
                 end

zUtil_Maths/gtMathsUpsampleVolume.m

@@ -6,11 +6,12 @@ function vol = gtMathsUpsampleVolume(vol, scale)
             vol{ii} = gtMathsUpsampleVolume(vol{ii}, scale);
         end
     else
-        vol = upsample(vol, scale);
+        vol = upsample_interp_interleaving(vol, scale);
     end
 end
 
 function vol = upsample(vol, scale)
+% The fastest!
     vol_in_size = size(vol);
     for ii_dim = numel(vol_in_size):-1:1
         indx{ii_dim} = 1:vol_in_size(ii_dim);
@@ -19,3 +20,21 @@ function vol = upsample(vol, scale)
     end
     vol = vol(indx{:});
 end
+
+function vol = upsample_interp_interleaving(vol, scale)
+% Faster than the custom made, bu still way slower than the simple one
+    vol = interpn(vol, scale-1, 'linear', 0);
+end
+
+function vol = upsample_interp(vol, scale)
+% It does exactly what the interleaving does, but it is here as a tutorial
+% for future reerence
+    vol_in_size = size(vol);
+    num_dims = numel(vol_in_size);
+    for ii_dim = num_dims:-1:1
+        indx_out{ii_dim} = 1:(1/scale):vol_in_size(ii_dim);
+    end
+    grid_out = cell(1, num_dims);
+    [grid_out{:}] = ndgrid(indx_out{:});
+    vol = interpn(vol, grid_out{:}, 'linear');
+end