message: Add y-flipping for GL in image viewer
  * Conventionally images have an origin at the top left, opposite to GL, so we
  want to flip the same as the replay proxy using GL as a proxy renderer for a
  non-GL API.
diff: @@ -113,6 +113,13 @@ public:
  void PickPixel(ResourceId texture, uint32_t x, uint32_t y, const Subresource &sub,
  CompType typeCast, float pixel[4])
  {
  + if(m_Props.localRenderer == GraphicsAPI::OpenGL)
  + {
  + TextureDescription tex = m_Proxy->GetTexture(texture);
  + uint32_t mipHeight = RDCMAX(1U, tex.height >> sub.mip);
  + y = (mipHeight - 1) - y;
  + }
  +
  m_Proxy->PickPixel(m_TextureID, x, y, sub, typeCast, pixel);
  }
  bool GetMinMax(ResourceId texid, const Subresource &sub, CompType typeCast, float *minval,
  @@ -129,6 +136,10 @@ public:
  {
  if(cfg.resourceId != m_TextureID && cfg.resourceId != m_CustomTexID)
  cfg.resourceId = m_TextureID;
  +
  + if(m_Props.localRenderer == GraphicsAPI::OpenGL)
  + cfg.flipY = !cfg.flipY;
  +
  return m_Proxy->RenderTexture(cfg);
  }
  uint32_t PickVertex(uint32_t eventId, int32_t width, int32_t height, const MeshDisplay &cfg,
  