Computer Graphics, Linux and Everything…

One thing I liked about Shake and miss in Nuke was its ability to process images easily from the command line. When working on automation tools for a pipeline, this was a very useful feature and a easy one to learn. After realizing that Nuke wasn’t built from a command line software and that such a feature surely won’t come anytime soon, I decided to spend some time writing my own tool to use Nuke from the exterior. It’s not a command line API, but it’s an API that can be used by any Python script anywhere in the pipeline.

Oblique, my employer, has allowed me to release it publicly. So here it is… nukeprocess.py.
Save this inside your custom python library or inside your Python’s site-packages directory. Since this is a tool for controlling an application via programming, I assume you know where to save a python file to use it. You will have to modify some parts to make sure it points to the right Nuke installation and to your own Python library.

It creates a Python script that can be run inside Nuke. It then starts Nuke and pipe the script to the STDIN, executes the script and exits Nuke. At the time of this writing, it works with Nuke 5.1v4.

If you find any bugs or have any comments about this tool, don’t hesitate to tell me. I’ve been using it in production for a few weeks now and I still find a few bugs from time to time. I would like it to be as solid as possible since Oblique pipeline will rely on it. Also, feel free to modify it to your own needs. I would appreciate if you told me what you did. In the Oblique internal version, I added a method to process on the render farm, but since our render manager API is custom made, I felt it was unnecessary for a public release.

Its usage is simple. You first create an instance of the NukeProcess class by giving it the name of the sequence you want to work with as well as its first frame, last frame and step. You then add nodes with the createNode() method by setting all the knob values with arguments. And execute the whole thing with the executeVerbose() method. The knob names you pass as args must be the scripting name. You can find them by hovering the mouse over any knob in Nuke, the tooltip is the script name.

Usage examples

#
# To resize a sequence of images, color correct it, and save to jpeg:
#
from nukeprocess import NukeProcess
np = NukeProcess("/someplace/someImageSequence.%04d.exr", 1, 100, 1)
np.createNode("Reformat", type='to box', box_width=1920, box_height=1080,
              box_fixed=True, resize='fit', black_outside=True)
np.createNode('Grade', black=.00537, white=.83)
np.createNode("Write", file="/someplace/someImageSequence_HD.%04d.jpg",
              file_type='jpeg', _jpeg_quality=1)
np.executeVerbose()

#
# To resize a sequence, offset it to frame 1 and put gray bars:
#
from nukeprocess import NukeProcess

# When declaring a empty string, it creates a Constant node instead of a Read.
np = nukeprocess.NukeProcess("", 1, sequence.getEnd()-sequence.getStart()+1,
                             color="{from_byte(64)}") 

# Use the addCode() method when you need to do something special.
np.addCode("f = nuke.addFormat('512 288 PreviewMovie')")
np.addCode("n.knob('format').setValue(f)")

# We save the node in a variable to use it later in the connectInput() method
np.saveNodeInVariable('constant') 

# sequence.getStart() and sequence.getEnd() come from another API,
# in this case a custom file browser.
np.createNode("Read", file="/somePlace/sequence.%04d.exr",
              first=sequence.getStart(), last=sequence.getEnd(),
              frame="frame+%d" % (sequence.getStart()+1))
np.createNode('Shuffle', alpha=6)
np.createNode("Reformat", type="to box", box_width=512, box_height=288,
              resize='fit', black_outside=True, box_fixed=True)

# The connectInput() method works on the previously added node.
np.createNode("Merge")
np.connectInput('constant')
np.createNode("Write", file="/somePlace/sequence_fit.%04d.exr",
              file_type="exr", compression='ZIP')

# to debug the script, you can print it and paste it in an interactive Nuke.
print np.getScript()
np.executeVerbose()

#
# To monitor the process:
#
from nukeprocess import NukeProcess
np = NukeProcess("/someplace/someImageSequence.%04d.exr", 1, 100, 1)
np.createNode("Write", file="/someplace/someImageSequence_HD.%04d.jpg",
              file_type='jpeg', _jpeg_quality=1)
oProcess = np.execute(1, 100, 1)
sOutLine = "."
while sOutLine != "":
    sOutLine = oProcess.stdout.readline()
    # Update process progress
    # Writing /someplace/someImageSequence_HD.0001.jpg took 1.08 seconds
    if sOutLine.startswith('Writing'):
        # Extract frame number from sOutLine
        try:
            iFrame = int(sOutLine.split()[1].rsplit('.')[-2])
        except:
            pass
        else:
            print("Processing frame: %d" % iFrame)

oProcess.wait()
result = oProcess.returncode

Documentation:

NukeProcess methods: