import numpy

def output_planes_to_cook(cop_node):
    return ("C",)

def required_input_planes(cop_node, output_plane):
    if output_plane == "C":
        return ("0", "C")
    return ()

def cook(cop_node, plane, resolution):
    input_cop = cop_node.inputs()[0]

    # Grab the pixels from the corresponding plane in the input, then build
    # a numpy array from the data.
    pixels = numpy.frombuffer(
        input_cop.allPixelsAsString(plane), dtype=numpy.float32).reshape(
        resolution[1], resolution[0], 3).copy()

    # Use numpy to scale all values by the brightness.
    pixels *= cop_node.evalParm("bright")

    # Store the contents of the numpy array back into the pixel data.
    cop_node.setPixelsOfCookingPlaneFromString(pixels.data)

reshape

Traceback (most recent call last):
File "", line 1, in 
File "", line 18, in cook
ValueError: total size of new array must be unchanged

pixels = numpy.frombuffer(
        input_cop.allPixelsAsString("C"), dtype=numpy.float32).reshape(
        input_cop.xRes(), input_cop.yRes(), 3).copy()