First pass on transforms. Committing to switch branches

Author: scotts

src/torchcodec/_core/Transform.cpp

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+// Copyright (c) Meta Platforms, Inc. and affiliates.
+// All rights reserved.
+//
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree.
+
+#include "src/torchcodec/_core/Transform.h"
+#include <torch/types.h>
+
+namespace facebook::torchcodec {
+
+std::string toStringFilterGraph(Transform::InterpolationMode mode) {
+  switch (mode) {
+    case Transform::InterpolationMode::BILINEAR:
+      return "BILINEAR";
+    case Transform::InterpolationMode::BICUBIC:
+      return "BICUBIC";
+    case Transform::InterpolationMode::NEAREST:
+      return "NEAREST";
+    default:
+      TORCH_CHECK(false, "Unknown interpolation mode: " + std::to_string(mode));
+  }
+}
+
+std::string Transform::getFilterGraphCpu() const {
+  return "scale=width=" + std::to_string(width_) +
+      ":height=" + std::to_string(height_) +
+      ":sws_flags=" + toStringFilterGraph(interpolationMode_);
+}
+
+} // namespace facebook::torchcodec

src/torchcodec/_core/Transform.h

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+// Copyright (c) Meta Platforms, Inc. and affiliates.
+// All rights reserved.
+//
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree.
+
+#pragma once
+
+#include <string>
+
+namespace facebook::torchcodec {
+
+class Transform {
+ public:
+  std::string getFilterGraphCpu() const = 0
+};
+
+class ResizeTransform : public Transform {
+ public:
+  ResizeTransform(int width, int height)
+      : width_(width),
+        height_(height),
+        interpolation_(InterpolationMode::BILINEAR) {}
+
+  ResizeTransform(int width, int height, InterpolationMode interpolation) =
+      default;
+
+  std::string getFilterGraphCpu() const override;
+
+  enum class InterpolationMode { BILINEAR, BICUBIC, NEAREST };
+
+ private:
+  int width_;
+  int height_;
+  InterpolationMode interpolation_;
+}
+
+} // namespace facebook::torchcodec