Send Image over Serial to Arduino and Display on TFT (ILI9341 Driver)

For a project I want to send an image generated in Matlab to an Arduino which has an external TFT Module (ILI9341-Driver with an 320x240 Display). I'm able to send the bytes over Serial, but the result is not really satisfying seen on the TFT. According to this tutorial: http://blog.miguelgrinberg.com/post/fun-with-the-arduino-esplora-a-digital-picture-frame

I'm pushing each pixel as a 2-Byte information containing the Colorcode over Serial (@115200 Baud). After Reading one row into a buffer on the arduino I display it. I'm having problems with synchronization and colors. I simply tried to adapt the code and ported it from python to matlab. Probably I made some bad mistackes. Any ideas?

Arduino code:

void loop()
{

    int bytes;
      if (Serial.available() > 0) {
          char cmd = Serial.read();
          switch (cmd) {
          case 'C': // connect
              Serial.println(x_size);
              Serial.println(y_size);
              break;
          case 'I': // image
              for (int row = 0; row < x_size; row++) {
                  bytes = x_size * 2; // one line has 240 pixel @ 2 byte per pixel (color)
                  char* p = (char*)line;
                  while (bytes > 0) { // serial port has a buffer of only 64 bytes, iterate until the entire line has been read
                      int n = Serial.readBytes(p, bytes);
                      if (n == 0) {
                          // timeout
                          return;
                      }
                      p += n;
                      bytes -= n;
                  }
                  for (int col = 0; col < y_size; col++)
                       Tft.setPixel(col,row,line[col]); 
              }
          }
      }
  }

and Matlab-Code:

z = generateSquare(x, x, .4);
z = uint8(z);
z = (cat(3, z, z, z));

%Wait until Arduino is ready for communication
result = 0;
while(result~=-1.0)
    result=fscanf(serial_port,'%d')  
end 

%send image data over serial port
fprintf(serial_port,'I'); %sends string via serial

for j=1:size(z, 2) % cols     
    for i=1:size(z, 1) % rows
        red = z(i, j, 1);
        green = z(i, j, 2);
        blue = z(i, j, 3);

          red = circshift(red,-3,2);
          green = circshift(green,-2,2);
          blue = circshift(blue,-3,2);

          data_1 = dec2bin(bitor(circshift(bitand(green,3), 5, 2), red));
          data_2 = dec2bin(bitor(circshift(blue , 3, 2), circshift(green ,-3, 2)));
          data = sprintf('%c%c', data_1, data_2);

          %dataString = num2str(z(i, j)); %converts to string
          fprintf(serial_port, data); %sends string via serial
      end
      disp(strcat('Row: ', num2str(j) ))
  end

The image is a 240x320 px matrix, three channels with a square in the middle of it (Black/White).