examples/xml-graph.py

   1 #!/usr/bin/env python
   2 from __future__ import print_function
   3
   4 from gi.repository import Gegl
   5 import sys
   6
   7 def check_operations(required_ops):
   8   known_ops = Gegl.list_operations()
   9
  10   missing_ops = []
  11
  12   for op in required_ops:
  13     if not op in known_ops:
  14       print("Could not find required operation:", op)
  15       missing_ops.append(op)
  16
  17   return not missing_ops
  18
  19 out_file_name = "xml-graph-output.png"
  20
  21 text_xml = """
  22 <?xml version='1.0' encoding='UTF-8'?>
  23 <gegl>
  24   <node operation='gegl:text'>
  25     <params>
  26       <param name='string'>Hello World</param>
  27       <param name='color'>rgb(1.0, 1.0, 1.0)</param>
  28       <param name='size'>24</param>
  29     </params>
  30   </node>
  31 </gegl>
  32 """
  33
  34 background_xml = """
  35 <?xml version='1.0' encoding='UTF-8'?>
  36 <gegl>
  37   <node operation='gegl:plasma'>
  38     <params>
  39       <param name='width'>256</param>
  40       <param name='height'>128</param>
  41     </params>
  42   </node>
  43 </gegl>
  44 """
  45
  46 if __name__ == '__main__':
  47   Gegl.init(sys.argv)
  48
  49   if not check_operations(["gegl:png-save", "gegl:text", "gegl:plasma", "gegl:translate"]):
  50     sys.exit(1)
  51
  52   graph = Gegl.Node()
  53
  54   # Load the graphs from xml, if they were in external files
  55   # we would use Gegl.Node.new_from_file() instead.
  56   lower_graph = Gegl.Node.new_from_xml(background_xml, "/")
  57   upper_graph = Gegl.Node.new_from_xml(text_xml, "/")
  58
  59   # Add a reference from our main node to the xml graphs so they
  60   # can't go out of scope as long as "graph" is alive.
  61   graph.add_child(lower_graph)
  62   graph.add_child(upper_graph)
  63
  64   # Center the upper graph on the lower graph
  65   text_bbox = upper_graph.get_bounding_box()
  66   background_bbox = lower_graph.get_bounding_box()
  67
  68   x_offset = max((background_bbox.width - text_bbox.width) / 2, 0)
  69   y_offset = max((background_bbox.height - text_bbox.height) / 2, 0)
  70
  71   translate = graph.create_child("gegl:translate")
  72   translate.set_property("x", x_offset)
  73   translate.set_property("y", y_offset)
  74
  75   upper_graph.connect_to("output", translate, "input")
  76
  77   # Use the "gegl:over" to combine the two graphs
  78   over = graph.create_child("gegl:over")
  79   lower_graph.connect_to("output", over, "input")
  80   translate.connect_to("output", over, "aux")
  81
  82   # Save the result to a png file
  83   save_node = graph.create_child ("gegl:png-save")
  84   save_node.set_property("path", out_file_name)
  85   over.connect_to("output", save_node, "input")
  86   save_node.process()
  87
  88   print("Save to", out_file_name)