From 6f7a97d0b46b5f5764220042fc8b4b1841b6fff0 Mon Sep 17 00:00:00 2001
From: Fidel Yin <fidel.yin@hotmail.com>
Date: Tue, 7 Nov 2023 20:29:40 -0500
Subject: [PATCH] Apply optimization proposed in
 https://github.com/ra1nty/DXcam/pull/62

---
 src/core/Processor.cpp | 50 ++++++++++++++++++++++++++++++++----------
 1 file changed, 39 insertions(+), 11 deletions(-)

diff --git a/src/core/Processor.cpp b/src/core/Processor.cpp
index 3f5783a..91abceb 100644
--- a/src/core/Processor.cpp
+++ b/src/core/Processor.cpp
@@ -6,20 +6,46 @@
 
 namespace DXCam {
 
-cv::Mat Processor::process(const DXGI_MAPPED_RECT &rect, const int width,
-                           const int height, const Region &region,
-                           const int rotation_angle) {
-    const auto pitch = rect.Pitch / 4;
+cv::Mat Processor::process(const DXGI_MAPPED_RECT &rect, int width, int height,
+                           const Region &region, const int rotation_angle) {
+    auto pitch = rect.Pitch;
 
+    // Pre-crop
+    int offset = 0;
+    switch (rotation_angle) {
+        case 0:
+            offset = region.top * pitch;
+            height = region.bottom - region.top;
+            break;
+        case 90:
+            offset = (width - region.right) * pitch;
+            width = region.right - region.left;
+            break;
+        case 180:
+            offset = (height - region.bottom) * pitch;
+            height = region.bottom - region.top;
+            break;
+        case 270:
+            offset = region.left * pitch;
+            width = region.right - region.left;
+            break;
+        default:
+            assert(false);  // never reach
+            break;
+    }
+    
+    pitch /= 4;  // number of channels
     cv::Mat image;
     if (rotation_angle == 0 || rotation_angle == 180) {
-        image = cv::Mat(height, pitch, CV_8UC4, rect.pBits);
+        image = cv::Mat(height, pitch, CV_8UC4, rect.pBits + offset);
     } else {
-        image = cv::Mat(width, pitch, CV_8UC4, rect.pBits);
+        image = cv::Mat(width, pitch, CV_8UC4, rect.pBits + offset);
     }
 
-    // TODO untested
+    // Rotation
     switch (rotation_angle) {
+        case 0:
+            break;
         case 90:
             cv::rotate(image, image, cv::ROTATE_90_CLOCKWISE);
             break;
@@ -30,13 +56,15 @@ cv::Mat Processor::process(const DXGI_MAPPED_RECT &rect, const int width,
             cv::rotate(image, image, cv::ROTATE_90_COUNTERCLOCKWISE);
             break;
         default:
+            assert(false);  // never reach
             break;
     }
 
-    if (region.right - region.left != width ||
-        region.bottom - region.top != height) {
-        image = image(cv::Range(region.top, region.bottom),
-                      cv::Range(region.left, region.right));
+    // Crop
+    if (region.right - region.left != width) {
+        image = image.colRange(region.left, region.right);
+    } else if (region.bottom - region.top != height) {
+        image = image.rowRange(region.top, region.bottom);
     }
 
     return image;