无法在C＃中转换类型的对象

Question

I am trying to read my images from my MS Access database into my eigenobjectrecognizer. But now, I am getting an error which is

Unable to cast object of type 'System.Byte[]' to type 'Emgu.CV.Image`2[Emgu.CV.Structure.Gray,System.Byte]'.

I dont know what is this error is about. Below is my code.

int count = reader.FieldCount;

while (reader.Read())
{
    labels.Add(reader["FaceName"].ToString());
    trainingImages.Add((Image<Gray,byte>)reader["FaceImage"]);
}   
if (TSTable.Rows.Count != 0)
{
    ////    //TermCriteria for face recognition with numbers of trained images like maxIteration
    MCvTermCriteria termCrit = new MCvTermCriteria(ContTrain, 0.001);

    ////Eigen face recognizer
    EigenObjectRecognizer recognizer = new EigenObjectRecognizer(
        trainingImages.ToArray(), //database faceimage list
        labels.ToArray(), //facename list
        3000,
        ref termCrit);

Can someone help me with this. I am trying this for more than a week already but still I cant get any solution. Thank you.

Answer 1

The problem is this line.

(Image<Gray,byte>)reader["FaceImage"]

The problem is that reader["FaceImage"] is of type byte[] and Image<Gray,byte>

1. Is not a base class of byte[]
2. Does not have an explicit nor implicit conversion operator from byte[] .

What you want is

{
    labels.Add(reader["FaceName"].ToString());
    byte[] buffer = (byte[]) reader["FaceImage"];
    Image<Gray,byte> image = new Image<Gray,byte>(buffer);
    trainingImages.Add(image);
} 

Answer 2

If reader["FaceImage"] is the image file then you need to create a new image from the file:

Image<Bgr, Byte> img1 = new Image<Bgr, Byte>(reader["FaceImage"]);
trainingImages.Add(image);