From f3e666b7bbbb18bb580dae166f5f15c3a32e9558 Mon Sep 17 00:00:00 2001
From: Peter Johnson <johnson.peter@gmail.com>
Date: Wed, 7 Dec 2022 10:36:40 -0800
Subject: [PATCH] [cscore] Convert YUYV and UYVY directly to grayscale (#4777)

This is significantly more efficient than converting by way of BGR.
---
 cscore/src/main/native/cpp/Frame.cpp | 65 +++++++++++++++++++++-------
 cscore/src/main/native/cpp/Frame.h   |  2 +
 2 files changed, 51 insertions(+), 16 deletions(-)

diff --git a/cscore/src/main/native/cpp/Frame.cpp b/cscore/src/main/native/cpp/Frame.cpp
index 881e82ec9a..e6f8e7c683 100644
--- a/cscore/src/main/native/cpp/Frame.cpp
+++ b/cscore/src/main/native/cpp/Frame.cpp
@@ -265,23 +265,12 @@ Image* Frame::ConvertImpl(Image* image, VideoMode::PixelFormat pixelFormat,
                  cur->pixelFormat == VideoMode::kGray) {
         return ConvertGrayToY16(cur);
       }
-      // If source is YUYV, UYVY, or RGB565, need to convert to BGR first
+      // If source is YUYV, UYVY, convert directly to Gray
+      // If RGB565, need to convert to BGR first
       if (cur->pixelFormat == VideoMode::kYUYV) {
-        // Check to see if BGR version already exists...
-        if (Image* newImage =
-                GetExistingImage(cur->width, cur->height, VideoMode::kBGR)) {
-          cur = newImage;
-        } else {
-          cur = ConvertYUYVToBGR(cur);
-        }
+        cur = ConvertYUYVToGray(cur);
       } else if (cur->pixelFormat == VideoMode::kUYVY) {
-        // Check to see if BGR version already exists...
-        if (Image* newImage =
-                GetExistingImage(cur->width, cur->height, VideoMode::kBGR)) {
-          cur = newImage;
-        } else {
-          cur = ConvertUYVYToBGR(cur);
-        }
+        cur = ConvertUYVYToGray(cur);
       } else if (cur->pixelFormat == VideoMode::kRGB565) {
         // Check to see if BGR version already exists...
         if (Image* newImage =
@@ -290,8 +279,8 @@ Image* Frame::ConvertImpl(Image* image, VideoMode::PixelFormat pixelFormat,
         } else {
           cur = ConvertRGB565ToBGR(cur);
         }
+        cur = ConvertBGRToGray(cur);
       }
-      cur = ConvertBGRToGray(cur);
       if (pixelFormat == VideoMode::kY16) {
         cur = ConvertGrayToY16(cur);
       }
@@ -407,6 +396,28 @@ Image* Frame::ConvertYUYVToBGR(Image* image) {
   return rv;
 }
 
+Image* Frame::ConvertYUYVToGray(Image* image) {
+  if (!image || image->pixelFormat != VideoMode::kYUYV) {
+    return nullptr;
+  }
+
+  // Allocate a grayscale image
+  auto newImage =
+      m_impl->source.AllocImage(VideoMode::kGray, image->width, image->height,
+                                image->width * image->height);
+
+  // Convert
+  cv::cvtColor(image->AsMat(), newImage->AsMat(), cv::COLOR_YUV2GRAY_YUYV);
+
+  // Save the result
+  Image* rv = newImage.release();
+  if (m_impl) {
+    std::scoped_lock lock(m_impl->mutex);
+    m_impl->images.push_back(rv);
+  }
+  return rv;
+}
+
 Image* Frame::ConvertUYVYToBGR(Image* image) {
   if (!image || image->pixelFormat != VideoMode::kUYVY) {
     return nullptr;
@@ -429,6 +440,28 @@ Image* Frame::ConvertUYVYToBGR(Image* image) {
   return rv;
 }
 
+Image* Frame::ConvertUYVYToGray(Image* image) {
+  if (!image || image->pixelFormat != VideoMode::kUYVY) {
+    return nullptr;
+  }
+
+  // Allocate a grayscale image
+  auto newImage =
+      m_impl->source.AllocImage(VideoMode::kGray, image->width, image->height,
+                                image->width * image->height);
+
+  // Convert
+  cv::cvtColor(image->AsMat(), newImage->AsMat(), cv::COLOR_YUV2GRAY_UYVY);
+
+  // Save the result
+  Image* rv = newImage.release();
+  if (m_impl) {
+    std::scoped_lock lock(m_impl->mutex);
+    m_impl->images.push_back(rv);
+  }
+  return rv;
+}
+
 Image* Frame::ConvertBGRToRGB565(Image* image) {
   if (!image || image->pixelFormat != VideoMode::kBGR) {
     return nullptr;
diff --git a/cscore/src/main/native/cpp/Frame.h b/cscore/src/main/native/cpp/Frame.h
index ab6170ff06..d5f537331e 100644
--- a/cscore/src/main/native/cpp/Frame.h
+++ b/cscore/src/main/native/cpp/Frame.h
@@ -195,7 +195,9 @@ class Frame {
   Image* ConvertMJPEGToBGR(Image* image);
   Image* ConvertMJPEGToGray(Image* image);
   Image* ConvertYUYVToBGR(Image* image);
+  Image* ConvertYUYVToGray(Image* image);
   Image* ConvertUYVYToBGR(Image* image);
+  Image* ConvertUYVYToGray(Image* image);
   Image* ConvertBGRToRGB565(Image* image);
   Image* ConvertRGB565ToBGR(Image* image);
   Image* ConvertBGRToGray(Image* image);