2 つの画像からカメラの外部要素を見つけようとしています。CameraCalibration の組み込み関数があり、シーンには既知の寸法 (3DSMAX で作成) があります。
チェス盤は 1000*1000 であるため、各正方形は 125*125 です。カメラは (0,0,3000) にあり、原点を中心とするチェス盤を真下に見ています。2 番目のイメージでは、カメラが平行移動 (-1500、0、-402) され、Y 軸上で 30° 回転して、チェス盤の中心を再び指しています。
GoodFeaturesToTrack は 81 個のコーナーを正しく識別します。
チェス盤の角の 3D ポイントを作成し、cvFindExtrinsicCameraParams2 を作成して組み込み関数を計算し、cvRodrigues2 を作成して回転行列を取得します。これがコードです
Imports Emgu.CV
Imports Emgu.CV.Structure
Imports Emgu.CV.CvInvoke
Imports Emgu.CV.CvEnum
Imports Emgu.CV.UI
Imports System.Drawing
Imports System.IO
Imports System.Diagnostics
Imports System.Math
Module main_
Sub Main()
Const MAXFEATURES As Integer = 100
Dim featuresA(0)() As PointF
Dim featuresB(0)() As PointF
Dim features As Integer = 0
Dim imgA As Emgu.CV.Image(Of Emgu.CV.Structure.Bgr, Byte)
Dim imgB As Emgu.CV.Image(Of Emgu.CV.Structure.Bgr, Byte)
Dim grayA As Emgu.CV.Image(Of Emgu.CV.Structure.Gray, Byte)
Dim grayB As Emgu.CV.Image(Of Emgu.CV.Structure.Gray, Byte)
Dim pyrBufferA As Emgu.CV.Image(Of Emgu.CV.Structure.Gray, Byte)
Dim pyrBufferB As Emgu.CV.Image(Of Emgu.CV.Structure.Gray, Byte)
Dim pointsA As Matrix(Of Single)
Dim pointsB As Matrix(Of Single)
Dim flags As Emgu.CV.CvEnum.LKFLOW_TYPE = Emgu.CV.CvEnum.LKFLOW_TYPE.DEFAULT
Dim imagesize As Size
Dim termcrit As New Emgu.CV.Structure.MCvTermCriteria(20, 0.03D)
Dim status As Byte() = Nothing
Dim errors As Single() = Nothing
Dim red As Bgr = New Bgr(Color.Red)
' Load chessboards
imgA = New Image(Of [Structure].Bgr, Byte)("chessboard centre.jpg")
imgB = New Image(Of [Structure].Bgr, Byte)("chessboard left.jpg")
grayA = imgA.Convert(Of Gray, Byte)()
grayB = imgB.Convert(Of Gray, Byte)()
' setup for feature detection
imagesize = cvGetSize(grayA)
pyrBufferA = New Emgu.CV.Image(Of Emgu.CV.Structure.Gray, Byte)(imagesize.Width + 8, imagesize.Height / 3)
pyrBufferB = New Emgu.CV.Image(Of Emgu.CV.Structure.Gray, Byte)(imagesize.Width + 8, imagesize.Height / 3)
features = MAXFEATURES
' Find features
featuresA = grayA.GoodFeaturesToTrack(features, 0.01, 25, 3)
grayA.FindCornerSubPix(featuresA, New System.Drawing.Size(10, 10), New System.Drawing.Size(-1, -1), termcrit)
features = featuresA(0).Length
' Compute optical flow. Not necessary here but good to remember
Emgu.CV.OpticalFlow.PyrLK(grayA, grayB, pyrBufferA, pyrBufferB, featuresA(0), New Size(25, 25), 3, termcrit, flags, featuresB(0), status, errors)
Debug.Assert(featuresA(0).GetUpperBound(0) = featuresB(0).GetUpperBound(0))
' Copy features to an easier-to-use matrix and get min/max to create 3d points
Dim minx As Double = Double.MaxValue
Dim miny As Double = Double.MaxValue
Dim maxx As Double = Double.MinValue
Dim maxy As Double = Double.MinValue
pointsA = New Matrix(Of Single)(features, 2)
pointsB = New Matrix(Of Single)(features, 2)
For i As Integer = 0 To features - 1
pointsA(i, 0) = featuresA(0)(i).X
pointsA(i, 1) = featuresA(0)(i).Y
pointsB(i, 0) = featuresB(0)(i).X
pointsB(i, 1) = featuresB(0)(i).Y
If pointsA(i, 0) < minx Then
minx = pointsA(i, 0)
End If
If pointsA(i, 1) < miny Then
miny = pointsA(i, 1)
End If
If pointsA(i, 0) > maxx Then
maxx = pointsA(i, 0)
End If
If pointsA(i, 1) > maxy Then
maxy = pointsA(i, 1)
End If
Next
' Create 3D object points that correspond to chessboard corners
' (The chessboard is 1000*1000, squares are 125*125)
Dim corners As Integer = Sqrt(features)
Dim obj As New Matrix(Of Double)(features, 3)
Dim squaresize2dx As Double = (maxx - minx) / 8 ' pixel width of a chessboard square
Dim squaresize2dy As Double = (maxy - miny) / 8 ' pixel height of a chessboard square
For i As Integer = 0 To features - 1
obj(i, 0) = Math.Round((pointsA(i, 0) - minx) / squaresize2dx) * 125 ' X=0, 125, 250, 375 ... 1000
obj(i, 1) = Math.Round((pointsA(i, 1) - miny) / squaresize2dy) * 125 ' idem in Y
obj(i, 2) = 0
' Debug.WriteLine(pointsA(i, 0) & " " & pointsA(i, 1) & " " & obj(i, 0) & " " & obj(i, 1) & " " & obj(i, 2)) ' Just to verify
Next
' These were calculated with CalibrateCamera using the same images
Dim intrinsics As New Matrix(Of Double)({{889.1647, 0.0, 318.3721},
{0.0, 888.5134, 238.4254},
{0.0, 0.0, 1.0}})
' Find extrinsics
Dim distortion As New Matrix(Of Double)({-0.036302, 2.008797, -29.674306, -29.674306})
Dim translation As New Matrix(Of Double)(3, 1)
Dim rotation As New Matrix(Of Double)(3, 1)
cvFindExtrinsicCameraParams2(obj, pointsA, intrinsics, distortion, rotation, translation, False)
' Convert rotation vector to rotation matrix
Dim rotmat As New Matrix(Of Double)(3, 3)
Dim jacobian As New Matrix(Of Double)(9, 3)
cvRodrigues2(rotation, rotmat, jacobian)
' From http://en.wikipedia.org/wiki/Rotation_representation paragraph "Conversion formulae between representations"
Dim yr As Double = Asin(-rotmat(2, 0))
Dim xr As Double = Asin(rotmat(2, 1) / Cos(yr))
Dim zr As Double = Asin(rotmat(1, 0) / Cos(yr))
End Sub
End Module
結果は正しくないようです。平行移動/回転を期待していましたが、次のようになります。
translation
208.394425348956
-169.447506344527
-654.273807995629
rotation
-0.0224937226554797
-2.13660350939653
-1.10542281290682
rotmat
-0.741100224945266 0.322885083546921 -0.588655824237707
-0.293966101915684 0.632206237134128 0.716867633983572
0.603617749499279 0.704315622822328 -0.373610915174894
xr=1.08307908108382 yr=-0.648031006135158 zr=-0.377625254910525
xr=62.0558602250101° yr=-37.1294416451609° zr=-21.636333343925°
誰かが私が間違っていることを知っていますか? ありがとう！