extract any image portion

You can use the Image.FromStream(); static method to extact an image from an in memory stream
supose that your image is stocked as bytes somewhere
for example 
byte[]DataImg
Here's the code:
//Put the DataImg array that contains the image in binary fromat in memory
MemoryStream oMemoryStream = new MemoryStream(DataImg);
//Then extract the image from this last one
Image myImage = Image.FromStream(oMemoryStream);
That's it