1 files changed, 92 insertions, 0 deletions
diff --git a/src/backends/RefWorkloads/ResizeBilinear.cpp b/src/backends/RefWorkloads/ResizeBilinear.cpp
new file mode 100644
index 0000000000..0bce3c7ed8
--- /dev/null
+++ b/src/backends/RefWorkloads/ResizeBilinear.cpp
@@ -0,0 +1,92 @@
+//
+// Copyright © 2017 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+
+#include "ResizeBilinear.hpp"
+
+#include "TensorBufferArrayView.hpp"
+
+#include <boost/numeric/conversion/cast.hpp>
+
+#include <cmath>
+#include <algorithm>
+
+namespace armnn
+{
+
+namespace
+{
+
+inline float Lerp(float a, float b, float w)
+{
+    return w * b + (1.f - w) * a;
+}
+
+}
+
+void ResizeBilinear(const float* in, const TensorInfo& inputInfo, float* out, const TensorInfo& outputInfo)
+{
+    // We follow the definition of TensorFlow and AndroidNN: the top-left corner of a texel in the output
+    // image is projected into the input image to figure out the interpolants and weights. Note that this
+    // will yield different results than if projecting the centre of output texels.
+
+    const unsigned int batchSize = inputInfo.GetShape()[0];
+    const unsigned int channelCount = inputInfo.GetShape()[1];
+
+    const unsigned int inputHeight = inputInfo.GetShape()[2];
+    const unsigned int inputWidth = inputInfo.GetShape()[3];
+    const unsigned int outputHeight = outputInfo.GetShape()[2];
+    const unsigned int outputWidth = outputInfo.GetShape()[3];
+
+    // How much to scale pixel coordinates in the output image, to get the corresponding pixel coordinates
+    // in the input image.
+    const float scaleY = boost::numeric_cast<float>(inputHeight) / boost::numeric_cast<float>(outputHeight);
+    const float scaleX = boost::numeric_cast<float>(inputWidth) / boost::numeric_cast<float>(outputWidth);
+
+    TensorBufferArrayView<const float> input(inputInfo.GetShape(), in);
+    TensorBufferArrayView<float> output(outputInfo.GetShape(), out);
+
+    for (unsigned int n = 0; n < batchSize; ++n)
+    {
+        for (unsigned int c = 0; c < channelCount; ++c)
+        {
+            for (unsigned int y = 0; y < outputHeight; ++y)
+            {
+                // Corresponding real-valued height coordinate in input image.
+                const float iy = boost::numeric_cast<float>(y) * scaleY;
+
+                // Discrete height coordinate of top-left texel (in the 2x2 texel area used for interpolation).
+                const float fiy = floorf(iy);
+                const unsigned int y0 = boost::numeric_cast<unsigned int>(fiy);
+
+                // Interpolation weight (range [0,1]).
+                const float yw = iy - fiy;
+
+                for (unsigned int x = 0; x < outputWidth; ++x)
+                {
+                    // Real-valued and discrete width coordinates in input image.
+                    const float ix = boost::numeric_cast<float>(x) * scaleX;
+                    const float fix = floorf(ix);
+                    const unsigned int x0 = boost::numeric_cast<unsigned int>(fix);
+
+                    // Interpolation weight (range [0,1]).
+                    const float xw = ix - fix;
+
+                    // Discrete width/height coordinates of texels below and to the right of (x0, y0).
+                    const unsigned int x1 = std::min(x0 + 1, inputWidth - 1u);
+                    const unsigned int y1 = std::min(y0 + 1, inputHeight - 1u);
+
+                    // Interpolation
+                    const float ly0 = Lerp(input.Get(n, c, y0, x0), input.Get(n, c, y0, x1), xw); // lerp along row y0.
+                    const float ly1 = Lerp(input.Get(n, c, y1, x0), input.Get(n, c, y1, x1), xw); // lerp along row y1.
+                    const float l = Lerp(ly0, ly1, yw);
+
+                    output.Get(n, c, y, x) = l;
+                }
+            }
+        }
+    }
+}
+
+} //namespace armnn