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#!/usr/bin/env python
from __future__ import print_function
from gi.repository import Gegl
import sys
def check_operations(required_ops):
known_ops = Gegl.list_operations()
missing_ops = []
for op in required_ops:
if not op in known_ops:
print("Could not find required operation:", op)
missing_ops.append(op)
return not missing_ops
out_file_name = "xml-graph-output.png"
text_xml = """
<?xml version='1.0' encoding='UTF-8'?>
<gegl>
<node operation='gegl:text'>
<params>
<param name='string'>Hello World</param>
<param name='color'>rgb(1.0, 1.0, 1.0)</param>
<param name='size'>24</param>
</params>
</node>
</gegl>
"""
background_xml = """
<?xml version='1.0' encoding='UTF-8'?>
<gegl>
<node operation='gegl:plasma'>
<params>
<param name='width'>256</param>
<param name='height'>128</param>
</params>
</node>
</gegl>
"""
if __name__ == '__main__':
Gegl.init(sys.argv)
if not check_operations(["gegl:png-save", "gegl:text", "gegl:plasma", "gegl:translate"]):
sys.exit(1)
graph = Gegl.Node()
# Load the graphs from xml, if they were in external files
# we would use Gegl.Node.new_from_file() instead.
lower_graph = Gegl.Node.new_from_xml(background_xml, "/")
upper_graph = Gegl.Node.new_from_xml(text_xml, "/")
# Add a reference from our main node to the xml graphs so they
# can't go out of scope as long as "graph" is alive.
graph.add_child(lower_graph)
graph.add_child(upper_graph)
# Center the upper graph on the lower graph
text_bbox = upper_graph.get_bounding_box()
background_bbox = lower_graph.get_bounding_box()
x_offset = max((background_bbox.width - text_bbox.width) / 2, 0)
y_offset = max((background_bbox.height - text_bbox.height) / 2, 0)
translate = graph.create_child("gegl:translate")
translate.set_property("x", x_offset)
translate.set_property("y", y_offset)
upper_graph.connect_to("output", translate, "input")
# Use the "gegl:over" to combine the two graphs
over = graph.create_child("gegl:over")
lower_graph.connect_to("output", over, "input")
translate.connect_to("output", over, "aux")
# Save the result to a png file
save_node = graph.create_child ("gegl:png-save")
save_node.set_property("path", out_file_name)
over.connect_to("output", save_node, "input")
save_node.process()
print("Save to", out_file_name)
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