Add template helpers to PixelFrame

Summary: These simple template methods make working with pixel data more expressive. No functional change.

Reviewed By: kiminoue7

Differential Revision: D53601784

fbshipit-source-id: a58857cda384e6cb2482a473b4560219ca49427f

vrs/utils/PixelFrame.cpp

@@ -633,7 +633,7 @@ bool PixelFrame::normalizeFrame(shared_ptr<PixelFrame>& normalizedFrame, bool gr
               normalizedFrame->wdata(), rdata(), getWidth(), getHeight(), getStride())) {
         return false;
       }
-      uint16_t* ptr = reinterpret_cast<uint16_t*>(normalizedFrame->wdata());
+      uint16_t* ptr = normalizedFrame->data<uint16_t>();
       const uint32_t pixelCount = getWidth() * getHeight() * componentCount;
       for (uint32_t i = 0; i < pixelCount; ++i) {
         ptr[i] <<= bitsToShift;
@@ -706,15 +706,15 @@ bool PixelFrame::normalizeFrame(shared_ptr<PixelFrame>& normalizedFrame, bool gr
     }
   } else if (format == PixelFormat::GREY16 && bitsToShift > 0) {
     // 12/10 bit pixel scaling to 16 bit
-    const uint16_t* srcPtr = reinterpret_cast<const uint16_t*>(rdata());
-    uint16_t* outPtr = reinterpret_cast<uint16_t*>(normalizedFrame->wdata());
+    const uint16_t* srcPtr = data<uint16_t>();
+    uint16_t* outPtr = normalizedFrame->data<uint16_t>();
     const uint32_t pixelCount = getWidth() * getHeight() * componentCount;
     for (uint32_t i = 0; i < pixelCount; ++i) {
       outPtr[i] = static_cast<uint16_t>(srcPtr[i] << bitsToShift);
     }
   } else if (XR_VERIFY(this->size() == 2 * normalizedFrame->size())) {
     // 16/12/10 bit pixel reduction to 8 bit
-    const uint16_t* srcPtr = reinterpret_cast<const uint16_t*>(rdata());
+    const uint16_t* srcPtr = data<uint16_t>();
     uint8_t* outPtr = normalizedFrame->wdata();
     const uint32_t pixelCount = getWidth() * getHeight() * componentCount;
     for (uint32_t i = 0; i < pixelCount; ++i) {

vrs/utils/PixelFrame.h

@@ -117,6 +117,14 @@ class PixelFrame {
   uint8_t* wdata() {
     return frameBytes_.data();
   }
+  template <class T>
+  inline const T* data(size_t byte_offset = 0) const {
+    return reinterpret_cast<const T*>(frameBytes_.data() + byte_offset);
+  }
+  template <class T>
+  inline T* data(size_t byte_offset = 0) {
+    return reinterpret_cast<T*>(frameBytes_.data() + byte_offset);
+  }
   size_t size() const {
     return frameBytes_.size();
   }