accept buffer pointer

Summary:
To be able to pass views over raw pixel buffers we cannot use the current API.

We cannot yet use std::span due to  old C++ version support
For now let's just allow to pass the const pointer to the raw buffer

Reviewed By: georges-berenger

Differential Revision: D63975867

fbshipit-source-id: e83d47437f73ca708976eac344f3077dbe54f5bb

vrs/utils/PixelFrame.h

@@ -239,6 +239,13 @@ class PixelFrame {
       vector<uint8_t>& outBuffer,
       uint32_t quality);
 
+  /// Same as previous version, with an external pixel buffer.
+  static bool jpgCompress(
+      const ImageContentBlockSpec& pixelSpec,
+      const uint8_t* pixels,
+      vector<uint8_t>& outBuffer,
+      uint32_t quality);
+
   /// Read a JPEG-XL encoded frame into the internal buffer.
   /// @return True if the frame type is supported & the frame was read.
   /// Returns false, if no decoder was installed, or the data couldn't be decoded correctly.

vrs/utils/PixelFrameJpeg.cpp

@@ -110,6 +110,15 @@ bool PixelFrame::jpgCompress(
     const vector<uint8_t>& pixels,
     vector<uint8_t>& outBuffer,
     uint32_t quality) {
+  return jpgCompress(pixelSpec, pixels.data(), outBuffer, quality);
+}
+
+/// Replace with a function accepting a std::span
+bool PixelFrame::jpgCompress(
+    const ImageContentBlockSpec& pixelSpec,
+    const uint8_t* pixels,
+    vector<uint8_t>& outBuffer,
+    uint32_t quality) {
   if (!XR_VERIFY(pixelSpec.getImageFormat() == ImageFormat::RAW) ||
       !XR_VERIFY(
           pixelSpec.getPixelFormat() == PixelFormat::RGB8 ||
@@ -119,14 +128,13 @@ bool PixelFrame::jpgCompress(
   const bool isGrey8 = (pixelSpec.getChannelCountPerPixel() == 1);
   long unsigned int jpegDataSize = 0;
   unsigned char* jpegData = nullptr;
-  const uint8_t* input = pixels.data();
 
   tjhandle _jpegCompressor = tjInitCompress();
 
   if (!XR_VERIFY(
           tjCompress2(
               _jpegCompressor,
-              input,
+              pixels,
               pixelSpec.getWidth(),
               pixelSpec.getStride(),
               pixelSpec.getHeight(),