From 661fb978f6bf7cae8c9a564a4ec5045daa1eb2b5 Mon Sep 17 00:00:00 2001
From: Ryan Heacock <rheacock@google.com>
Date: Tue, 13 Jun 2023 10:31:29 -0700
Subject: [PATCH] Adds support for PCACompute

This PR adds support for PCACompute via wrapping one of the opencv
versions with this function signature. A smoke test has been added that
calls the wrapped function and verifies that the parameters are being
passed correctly.

In opencv there are four versions with this function signature, I have
chosen to wrap (what I think is) the most common with the most
parameters.

Link to supported functionality now: https://docs.opencv.org/4.x/d2/de8/group__core__array.html#ga4e2073c7311f292a0648f04c37b73781
---
 ROADMAP.md   |  2 +-
 core.cpp     |  4 ++++
 core.go      | 14 ++++++++++++++
 core.h       |  1 +
 core_test.go | 23 +++++++++++++++++++++++
 5 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/ROADMAP.md b/ROADMAP.md
index 1557b5db..b11e4b85 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -18,7 +18,7 @@ Your pull requests will be greatly appreciated!
         - [ ] [Mahalanobis](https://docs.opencv.org/master/d2/de8/group__core__array.html#ga4493aee129179459cbfc6064f051aa7d)
         - [ ] [mulTransposed](https://docs.opencv.org/master/d2/de8/group__core__array.html#gadc4e49f8f7a155044e3be1b9e3b270ab)
         - [ ] [PCABackProject](https://docs.opencv.org/master/d2/de8/group__core__array.html#gab26049f30ee8e94f7d69d82c124faafc)
-        - [ ] [PCACompute](https://docs.opencv.org/master/d2/de8/group__core__array.html#ga4e2073c7311f292a0648f04c37b73781)
+        - [X] [PCACompute](https://docs.opencv.org/master/d2/de8/group__core__array.html#ga4e2073c7311f292a0648f04c37b73781)
         - [ ] [PCAProject](https://docs.opencv.org/master/d2/de8/group__core__array.html#ga6b9fbc7b3a99ebfd441bbec0a6bc4f88)
         - [ ] [PSNR](https://docs.opencv.org/master/d2/de8/group__core__array.html#ga07aaf34ae31d226b1b847d8bcff3698f)
         - [ ] [randn](https://docs.opencv.org/master/d2/de8/group__core__array.html#gaeff1f61e972d133a04ce3a5f81cf6808)
diff --git a/core.cpp b/core.cpp
index 97d0f8f2..79ef8a29 100644
--- a/core.cpp
+++ b/core.cpp
@@ -504,6 +504,10 @@ void Mat_EigenNonSymmetric(Mat src, Mat eigenvalues, Mat eigenvectors) {
     cv::eigenNonSymmetric(*src, *eigenvalues, *eigenvectors);
 }
 
+void Mat_PCACompute(Mat src, Mat mean, Mat eigenvalues, Mat eigenvectors, int maxComponents) {
+    cv::PCACompute(*src, *mean, *eigenvalues, *eigenvectors, maxComponents);
+}
+
 void Mat_Exp(Mat src, Mat dst) {
     cv::exp(*src, *dst);
 }
diff --git a/core.go b/core.go
index 3f30900b..be51a59b 100644
--- a/core.go
+++ b/core.go
@@ -1219,6 +1219,20 @@ func EigenNonSymmetric(src Mat, eigenvalues *Mat, eigenvectors *Mat) {
 	C.Mat_EigenNonSymmetric(src.p, eigenvalues.p, eigenvectors.p)
 }
 
+// PCACompute performs PCA.
+//
+// The computed eigenvalues are sorted from the largest to the smallest and the corresponding
+// eigenvectors are stored as eigenvectors rows.
+//
+// Note: Calling with maxComponents == 0 (opencv default) will cause all components to be retained.
+//
+// For further details, please see:
+// https://docs.opencv.org/4.x/d2/de8/group__core__array.html#ga27a565b31d820b05dcbcd47112176b6e
+//
+func PCACompute(src Mat, mean *Mat, eigenvalues *Mat, eigenvectors *Mat, maxComponents int) {
+	C.Mat_PCACompute(src.p, mean.p, eigenvalues.p, eigenvectors.p, C.int(maxComponents))
+}
+
 // Exp calculates the exponent of every array element.
 //
 // For further details, please see:
diff --git a/core.h b/core.h
index 19dc3ed5..12f1c318 100644
--- a/core.h
+++ b/core.h
@@ -379,6 +379,7 @@ void Mat_DFT(Mat m, Mat dst, int flags);
 void Mat_Divide(Mat src1, Mat src2, Mat dst);
 bool Mat_Eigen(Mat src, Mat eigenvalues, Mat eigenvectors);
 void Mat_EigenNonSymmetric(Mat src, Mat eigenvalues, Mat eigenvectors);
+void Mat_PCACompute(Mat src, Mat mean, Mat eigenvalues, Mat eigenvectors, int maxComponents);
 void Mat_Exp(Mat src, Mat dst);
 void Mat_ExtractChannel(Mat src, Mat dst, int coi);
 void Mat_FindNonZero(Mat src, Mat idx);
diff --git a/core_test.go b/core_test.go
index 64b795f3..633c311a 100644
--- a/core_test.go
+++ b/core_test.go
@@ -2070,6 +2070,29 @@ func TestMatEigenNonSymmetric(t *testing.T) {
 	eigenvalues.Close()
 }
 
+func TestPCACompute(t *testing.T) {
+	src := NewMatWithSize(10, 10, MatTypeCV32F)
+	// Set some source data so the PCA is done on a non-zero matrix.
+	src.SetFloatAt(0, 0, 17)
+	src.SetFloatAt(2, 1, 5)
+	src.SetFloatAt(9, 9, 25)
+	mean := NewMat()
+	eigenvalues := NewMat()
+	eigenvectors := NewMat()
+	maxComponents := 2
+	PCACompute(src, &mean, &eigenvalues, &eigenvectors, maxComponents)
+	if mean.Empty() || eigenvectors.Empty() || eigenvalues.Empty() {
+		t.Error("TestPCACompute should not have empty eigenvectors or eigenvalues.")
+	}
+	if eigenvectors.Rows() > maxComponents {
+		t.Errorf("TestPCACompute unexpected numComponents, got=%d, want<=%d", eigenvectors.Rows(), maxComponents)
+	}
+	src.Close()
+	mean.Close()
+	eigenvectors.Close()
+	eigenvalues.Close()
+}
+
 func TestMatExp(t *testing.T) {
 	src := NewMatWithSize(10, 10, MatTypeCV32F)
 	dst := NewMat()