Byte order, big-endian, little-endian¶
This example demonstrates some issues with big-endian and little-endian .raw files.
The pi2 system always assumes that .raw files are read in native byte order of the host computer. If this is not the case, the byte order can be changed using swapbyteorder command
def big_endian_and_little_endian(): """ Demonstrates how to change the endianness of pixel values. """ # The images are in the native byte order geometry = pi.newimage(ImageDataType.UINT16, 100, 100) pi.ramp(geometry, 1) # By default, images are written in the native byte order. # This usually means little endian at the time this was written, and at the # processors this code has ever run. pi.writeraw(geometry, output_file("little_endian_ramp")) # Change to big endian format can be made by running swapbyteorder command pi.swapbyteorder(geometry) pi.writeraw(geometry, output_file("big_endian_ramp")) # NOTE: Here the geometry image is stored in big endian format, and you cannot do # any calculations on it until you run the swapbyteorder command on it again! # For example, writing something else than .raw files for image in non-native byte # order does not make sense! The .tif file saved below will # contain pixel values in wrong byte order. pi.writetif(geometry, output_file("big_endian_ramp.tif"))