The Image class is not a POD type, therefore you can not send it using MPI_Send
The simplest way to do it is to send BLOB data, which you can get from the Image object, but it might not be optimal. So, do it like this :
Image testImage;
// read in the file
testImage.read("image.png");
Blob blob;
testImage.write( & blob );
int size = blob.length();
MPI_Send( &size, sizeof( size ), MPI_BYTE, i , 100, MPI_COMM_WORLD);
MPI_Send( blob.data(), blob.length(), MPI_BYTE, i , 100, MPI_COMM_WORLD);
To receive :
int size = 0;
MPI_Recv( &size, sizeof( size ), MPI_BYTE, 0, 100, MPI_COMM_WORLD, &status);
std::vector< unsigned char > tempBuffer( size, 0 );
MPI_Recv( &tempBuffer[0], tempBuffer.size(), MPI_BYTE, 0, 100, MPI_COMM_WORLD, &status);
Blob blob( &tempBuffer[0], tempBuffer.size());
