Fixes #457 Bitmap.ToArray() does not handle images with odd width

Author: BramClocktimizer

src/NumSharp.Bitmap/np_.extensions.cs

@@ -87,14 +87,14 @@ public static unsafe NDArray ToNDArray(this System.Drawing.Bitmap image, bool fl
                     {
                         if (bmpData.Stride / bmpData.Width == 4) //1byte-per-color
                         {
-                            return ret.reshape(1, bmpData.Height, bmpData.Width, bmpData.Stride / bmpData.Width) //reshape
+                            return ReshapeFlatData(ret, bmpData) // reshape
                                        [Slice.All, Slice.All, Slice.All, new Slice(stop: 3)] //slice
                                       .flat; //flatten
                         }
 
                         if (bmpData.Stride / bmpData.Width == 8) //2bytes-per-color
                         {
-                            return ret.reshape(1, bmpData.Height, bmpData.Width, bmpData.Stride / bmpData.Width) //reshape
+                            return ReshapeFlatData(ret, bmpData) // reshape
                                        [Slice.All, Slice.All, Slice.All, new Slice(stop: 6)] //slice
                                       .flat; //flatten
                         }
@@ -106,7 +106,7 @@ public static unsafe NDArray ToNDArray(this System.Drawing.Bitmap image, bool fl
                 }
                 else
                 {
-                    ret = ret.reshape(1, bmpData.Height, bmpData.Width, bmpData.Stride / bmpData.Width); //reshape
+                    ret = ReshapeFlatData(ret, bmpData); //reshape
                     if (discardAlpha)
                     {
                         if (ret.shape[3] == 4) //1byte-per-color
@@ -122,6 +122,25 @@ public static unsafe NDArray ToNDArray(this System.Drawing.Bitmap image, bool fl
             }
         }
 
+        /// <summary>
+        /// Reshapes the flat data to match the size of the bitmap.
+        /// </summary>
+        /// <param name="ret">flat 1-dimensional array containing the bitmap data</param>
+        /// <param name="bmpData">Source bitmap</param>
+        /// <returns>An 4-dimensional NDArray that holds the bitmap data contained in `ret`</returns>
+        private static NDArray ReshapeFlatData(NDArray ret, BitmapData bmpData)
+        {
+            var colorBytes = bmpData.Stride / bmpData.Width;
+            var strideWidth = bmpData.Stride / colorBytes; // For odd widths, this width is not equal to bmpData.Width
+            ret = ret.reshape(1, bmpData.Height, strideWidth, bmpData.Stride / bmpData.Width);
+            if (strideWidth != bmpData.Width)
+            {
+                ret = ret[Slice.All, Slice.All, new Slice(stop: bmpData.Width), new Slice(stop: colorBytes)];
+            }
+
+            return ret;
+        }
+
         /// <summary>
         ///     Creates <see cref="NDArray"/> from given <see cref="Image"/>.
         /// </summary>

test/NumSharp.UnitTest/NumSharp.Bitmap/BitmapWithAlphaTests.cs

@@ -40,6 +40,15 @@ public void ToNDArray_Case4()
             var nd = bitmap.ToNDArray(discardAlpha: false, copy: false);
             nd.Should().BeShaped(1, 165, 400, 4);
         }
+        
+        
+        [TestMethod]
+        public void ToNDArray_Odd_Width()
+        {
+            var bitmap = EmbeddedBitmap("odd-width");
+            var nd = bitmap.ToNDArray(discardAlpha: false, copy: false);
+            nd.Should().BeShaped(1, 554, 475, 3);
+        }
 
         [TestMethod]
         public void ToNDArray_Case5_flat()

test/NumSharp.UnitTest/NumSharp.Bitmap/resources/odd-width.png

@@ -24,6 +24,8 @@
     <EmbeddedResource Remove="data\**" />
     <None Remove="Backends\Unmanaged\Iterators\**" />
     <None Remove="data\**" />
+    <None Remove="NumSharp.Bitmap\resources\odd-width.png" />
+    <EmbeddedResource Include="NumSharp.Bitmap\resources\odd-width.png" />
   </ItemGroup>
 
   <ItemGroup>