.. meta::
    :description: Code snippets pad channel Numpy array

How to pad a Channel
====================

In this example, we access the Channel Numpy array of a source dataset and copy it to another section of a
destination dataset, in order to pad a few slices at the lower Z and at the higher Z.

The source dataset is named ``sourceChannel``::

    # Creating the destination Channel
    destinationChannel = sourceChannel.copy()

    # Adapting the shape of the destination Channel to contain the padding slices
    countPaddingSlicesOnEachSide = 10
    originalZSize = sourceChannel.getZSize()
    destinationChannel.setZSize(originalZSize + 2*countPaddingSlicesOnEachSide)
    destinationChannelBox = destinationChannel.getBox()
    destinationChannelDirection2 = destinationChannelBox.getDirection2()
    destinationChannelSpacingDirection2 = destinationChannelBox.getDirection2Spacing()
    destinationChannelOrigin = destinationChannelBox.getOrigin()
    destinationChannelNewOrigin = destinationChannelOrigin - countPaddingSlicesOnEachSide*destinationChannelSpacingDirection2*destinationChannelDirection2
    destinationChannelBox.setOrigin(destinationChannelNewOrigin)
    destinationChannel.setBox(destinationChannelBox)
    destinationChannel.initializeData()

    # Accessing the data of the source channel and the destination channel
    timeStep = 0
    npDataSourceChannel = sourceChannel.getNDArray(timeStep)
    npDataDestinationChannel = destinationChannel.getNDArray(timeStep)

    # Copying common region data
    npDataDestinationChannel[countPaddingSlicesOnEachSide:-countPaddingSlicesOnEachSide, :, :] = npDataSourceChannel[:, :, :]

    # Padding at lower Z
    for zIndex in range(countPaddingSlicesOnEachSide):
        npDataDestinationChannel[zIndex, :, :] = npDataSourceChannel[0, :, :]

    # Padding at higher Z
    for zIndex in range(countPaddingSlicesOnEachSide):
        npDataDestinationChannel[-zIndex-1, :, :] = npDataSourceChannel[-1, :, :]

    # Setting the properties of the new channel
    destinationChannel.setTitle(sourceChannel.getTitle() + ' (Padded)')

    # Publishing the new object
    destinationChannel.publish()