Nuke: This snippet of code takes all read nodes within a given Nuke comp and resizes the images and then saves them out to either png or jpeg.

Resize Images and Save New Format | .py

#import a python module so we can do the search&replace stuff
import re
import os

#select all nodes in the root graph
nuke.selectAll()

############# variables
writeNodeList = [];
imgType = "png" # use either 'png' / 'jpeg'
resizeType = "percent" # use either 'pixel' / 'percent'
sizePercent = .5 # use value between '0.1 - 10.0'
sizePixel = 1024 # only supports square images in this mode

#loop through all selected read nodes to
for n in nuke.selectedNodes('Read'):

	#get the full filepath
	filepath = n.knob('file').value()

	#replace extension with .jpg
	#(root, ext) = os.path.splitext(filepath)
	root = os.path.splitext(filepath)[0]


	#############
	# Reformt
	# percentage: uses a value between 0 - 10 to resize image
	# pixel: uses a specified pixel value to control width/height of resized image
	#############
	sizeNode = nuke.createNode('Reformat')
	sizeNode.setInput(0,n)

	if resizeType == "percent":
		sizeNode["type"].setValue("scale")
		sizeNode["scale"].setValue(sizePercent)

	if resizeType == "pixel":
		sizeNode["type"].setValue("to box")
		sizeNode["box_width"].setValue(sizePixel)
		sizeNode["box_height"].setValue(sizePixel)
		sizeNode["box_fixed"].setValue(False)
		sizeNode["resize"].setValue("fit")
		sizeNode["black_outside"].setValue(True)
	

	#############
	# Save Image Output
	# jpeg: saves a jpeg out with highest qualit
	# png: saves our png with lossless compression
	#############
	writeNode = nuke.createNode('Write')
	writeNode.setInput(0,sizeNode)

	if imgType == "jpeg":
		newFilepath = root + ".jpeg"
		
		writeNode.knob('file').fromUserText(newFilepath)
		writeNode["_jpeg_quality"].setValue(1.0)
		writeNode["channels"].setValue("rgb")
		writeNode["colorspace"].setValue("sRGB")
		writeNodeList.append(writeNode);

	if imgType == "png":
		newFilepath = root + ".png"
		
		writeNode.knob('file').fromUserText(newFilepath)
		writeNode["datatype"].setValue("8_bit")
		writeNodeList.append(writeNode);

for n in writeNodeList:
	nuke.execute(n, 1, 1)