Add CreateTensorFromImageFileAlt function (migueldeicaza#421)

captainst · migueldeicaza · commit 2ac92fcd714a · 2019-10-25T15:46:55.000-04:00
An alternative function that convert directly the pixel values of a bitmap to a (1,H,W,3) shape matrix, which is converted to a tensor.
This function is fast and gives better results for Object Detection Example.
diff --git a/Examples/ExampleCommon/ImageUtil.cs b/Examples/ExampleCommon/ImageUtil.cs
@@ -66,5 +66,33 @@ private static TFGraph ConstructGraphToNormalizeImage (out TFOutput input, out T
 			
 			return graph;
 		}
+		
+		public static unsafe TFTensor CreateTensorFromImageFileAlt(string inputFileName, TFDataType destinationDataType = TFDataType.Float)
+                {
+                  Bitmap bitmap = new Bitmap(inputFileName);
+
+                  BitmapData data = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
+
+                  var matrix = new byte[1, bitmap.Height, bitmap.Width, 3];
+
+                  byte* scan0 = (byte*)data.Scan0.ToPointer();
+            
+                  for (int i = 0; i < data.Height; i++)
+                  {
+                      for (int j = 0; j < data.Width; j++)
+                      {
+                          byte* pixelData = scan0 + i * data.Stride + j * 3;
+                          matrix[0, i, j, 0] = pixelData[2];
+                          matrix[0, i, j, 1] = pixelData[1];
+                          matrix[0, i, j, 2] = pixelData[0];
+                      }
+                  }
+
+                  bitmap.UnlockBits(data);
+
+                  TFTensor tensor = matrix;
+
+                  return tensor;
+                }
 	}
 }
