bpy_TestRender_UI_only.py

# Render Test

import bpy
from bpy.props import *


#Setup Radio Button Enum Props
bpy.types.Scene.rtSizeEnum = bpy.props.EnumProperty( \
  items = [('Half', 'Half', 'Half the size of the render rez'),\
  ('Quarter', 'Quarter', 'Quarter the size of the render rez'),\
  ('Thumbnail', 'Thumbnail', 'Thumbnail size of the render rez')],\
  name = 'trSize', default = 'Quarter')


class RenderTestPanel(bpy.types.Panel):
    bl_label = "Render Test"
    bl_space_type = "PROPERTIES"
    bl_region_type = "WINDOW"
    bl_context = "render"
 
    def draw(self, context):
        layout = self.layout 
        scn = bpy.context.scene
        rd = scn.render

        # Size selection
        row = layout.row()
        row.label(text="Reduce resolution to:")
        row = layout.row(align=True)
        row.alignment = 'EXPAND'
        layout.row().prop(context.scene,'rtSizeEnum', expand=True)

        split = layout.split()
        col = split.column()
        sub = col.column(align=True)
        sub.label(text="Resolution:")
        sub.prop(rd, "resolution_x", text="X")
        sub.prop(rd, "resolution_y", text="Y")
        sub.prop(rd, "resolution_percentage", text="")

        # Segment range set, default all
        layout.label(text="Segment Range:")
        row = layout.row(align=True)
        row.prop(scn, "frame_start")
        row.prop(scn, "frame_end")

        # Call render
        row = layout.row()
        #row.operator( "render.render" )
        row.operator( "bpt.render_test_op" )
 
        #if context.scene.rtSizeEnum == 'Half':

class RenderTestOperator(bpy.types.Operator):
    bl_idname = "bpt.render_test_op"
    bl_label = "Render Test"
 
    def execute(self, context):
        self.report({'INFO'}, "Test Render initiated! ")
        print(context.scene.rtSizeEnum)

        # note .ops. scope change from panel button version
        #bpy.ops.render.render(scene="Scene") NOPE!
        #bpy.ops.render.render(text="Render") NOPE!
        #rnl = context.scene.render.layers.active NOPE!
        #bpy.ops.scene.render NOPE!
        #context.scene.render NOPE!
        #context.scene.render.render NOPE!
        #context.scene.render() NOPE!
        #context.scene.render.render() NOPE!

        #bpy.ops.render.render() NOPE!
        #bpy.ops.render.view_show() NOPE!

        # NOTE: set output path edit box with a filename other wise it will write .png as a hidden file
        scn = bpy.context.window.screen.scene
        bpy.ops.render.render(animation=False, write_still=True, layer="", scene=scn.name)
        #bpy.ops.render.view_show()
        # below works also all filled in...
        #bpy.ops.render.render(animation=False, write_still=True, layer="", scene=bpy.context.window.screen.scene.name)

        return {'FINISHED'}
 
def register():
    bpy.utils.register_class( RenderTestPanel )
    bpy.utils.register_class( RenderTestOperator )
 
def unregister():
    bpy.utils.register_class( RenderTestPanel )
    bpy.utils.register_class( RenderTestOperator )
 
if __name__ == "__main__":
    register()