title: Transfer QImage to python numpy
body: <p>I'm sending a QImage (as a byte array) from my C++ qt app through a socket to a python process. I want to restore the RGB channels to a numpy array representing the image. However, I couldn't find any documentation on how the Qimage is stored or sent when writing it to a bytearray. I would prefer not using Qt on the python side.</p>
  
  <p>The code for sending the raw bytes is already working, I'm struggling with understanding the composition of the raw data back to the RGB channels. 
  The image is BMP, with QImage::Format_RGB32, using Qt 5.7, python 2.7.12.</p>
  
  <p>So far I'm getting that the amount of bytes is 3*width*height so I assume it is a byte for each of R,G,B, but there are 54 more bytes that I don't know what they rerpresnt. Also, If the image is RGB32, shouldn't it be 4 bytes per pixel? I don't have an alpha channel, so it's weird.</p>