Scales all strokes in a rotopaint node by a specified scale: expects a layer full of strokes that have all been scaled by the specified amount from a center of 0,0

reformat_paint.py

## Adjust size of all brush stokes in a layer
## Expects a single layer in the rotopaint node containing strokes that want to be scaled.
## This script scales the brushsize and source transform by the scale value

_SCALE_ = 1.53706293

rn = nuke.selectedNode()
cKnob = rn["curves"]
rootLayer = cKnob.rootLayer

layers = [elem for elem in rootLayer if isinstance(elem, nuke.rotopaint.Layer)]

for layer in layers:
    for stroke in layer:
        print stroke.name
        stroke_attr = stroke.getAttributes()
        brushsize = stroke_attr.getCurve('bs')
        curValue = brushsize.constantValue
        newValue = curValue*_SCALE_
        stroke_attr.remove('bs')
        stroke_attr.add('bs', newValue)
        
        src_translate_x = stroke_attr.getCurve('stx').constantValue
        src_translate_y = stroke_attr.getCurve('sty').constantValue

        new_src_translate_x = src_translate_x * _SCALE_
        new_src_translate_y = src_translate_y * _SCALE_

        stroke_attr.remove('stx')
        stroke_attr.remove('sty')

        stroke_attr.add('stx', new_src_translate_x)
        stroke_attr.add('sty', new_src_translate_y)

        cKnob.changed()