Python "it" Scripting
Adding to the Commands Menu

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Introduction

Menu items can be added to the Commands menu of the 'it' window relatively easily. Pixar's document,
    "it" Custom Commands
provides a clear explanation of how it is done. This tutorial presents an example of a python script that can be directly executed from the Commands menu - figure 1. It does not use any dialogs, windows or any other UI elements. For examples of custom commands that use a UI refer to these links,
    save all
    histogram

Figure 1

To function as a menu item the Thumbnail.py script must,
    - implement a sub-class of Pixar's it.It3Command base class,
    - assign a value (the menu item label) to the m_menuPath instance variable,
    - implement a method called Invoke(), and finally,
    - call itself via it.commands.append(Thumbnail).

The python code is shown next.

import it, os
from it.It3Command import It3Command
  
class Thumbnail(It3Command):
    def __init__(self):
        self.m_menuPath = 'Commands/Save Thumbnail'
        
    def Invoke(self):
        self.save_thumbnail()
  
    def save_thumbnail(self, gamma=1.0,quality=100):   
        element = it.GetCurrentElement()
        image_name = element.GetLabel() + '.jpg'
        cwdpath = os.getcwd()
        path = os.path.join(cwdpath, image_name)
        self.saveImage(element, path, 2.2, 100) 
        it.app.Info('The thumbnail has been saved as "%s"' % os.path.abspath(path))
        it.app.RaiseLogWindow()
        
    def saveImage(self, element,path,gamma,quality):
        image = element.GetImage()
        image = image.Gamma(gamma);
        
        # dimensions, True preserve aspect ratio, True crop to preserve aspect ratio
        image = image.Reformat([0,150,0,150], True, True)
        
        image.SetMetaDataItem('JPEG_QUALITY', quality)
        image.Save(path, ice.constants.FMT_JPEG)    
it.commands.append(Thumbnail)

Installing & Loading the Script

Save the python script in your custom "it" scripts directory. For example, the "RfM: Customizing" tutorial recommends using this directory,
    maya/rfm_scripts/image_tool/Thumbnail.py
The users custom "it.ini" script must install the python script when Maya loads the RenderMan_for_Maya plugin. The "RfM: Customizing" tutorial recommends using the following path,
    maya/rfm_scripts/image_tool/it.ini

The "it.ini" script should contain a command of the following form (Windows).

    LoadExtension python "C:/Users/YOUR_NAME/Documents/maya/rfm_scripts/image_tool//Thumbnail.py"

If the user has set an environment variable called MAYA_USER_DIR that "points" to the location of their maya directory the following command can be used.

    LoadExtension python "[GetEnv MAYA_USER_DIR]/rfm_scripts/image_tool/Thumbnail.py"