import os, sys, subprocess
import maya.cmds as cmds
import maya.mel as mel

# Output functions
def __errorMsg(message):
	mel.eval((u'error("%s")') % message)

def __warningMsg(message):
	mel.eval((u'warning("%s")') % message)

def invokeImfDisp(fileName, channel):
	"""
	Display given image file using imf_disp that is packaged with Maya.

	If the image is an OpenEXR and a channel is defined then that channel
	will be displayed, otherwise the default channels (R,G,B,A) will be used.
	"""
	if os.path.exists(fileName):
		# create imf_copy command
		imfDispBin = ('%s/bin/imf_disp')
		if cmds.about(mac=True):
			imfDispBin += ('.app/Contents/MacOS/imf_disp')
		cmdAndArgs = [ imfDispBin % mel.eval(('getenv("MENTALRAY_LOCATION")')) ]
		if channel:
			cmdAndArgs.append(('--layer=%s') % channel)

		# modify file name on Windows as imf_disp is picky
		finalFileName = fileName
		if cmds.about(win=True):
			finalFileName = os.path.normpath(fileName)
		cmdAndArgs.append(finalFileName)

		# encode params to subprocess in the system encoding because
		# the subprocess module does not play nice with unicode strings
		fse = sys.getfilesystemencoding()
		try:
			cmdAndArgs = [ arg.encode(fse) if isinstance(arg, unicode) else arg for arg in cmdAndArgs ]
		except:
			message = mel.eval('getPluginResource("Mayatomr", "kEncodingError")')
			message %= ' '.join(cmdAndArgs)
			__warningMsg(message)

		# run command in non-blocking manner, user will be responsible
		# for closing new window
		try:
			subprocess.Popen(cmdAndArgs)
		except:
			message = mel.eval('getPluginResource("Mayatomr", "kRunProcessFailed")')
			message %= ' '.join(cmdAndArgs)
			__errorMsg(message)
	else:
		message = mel.eval('getPluginResource("Mayatomr", "kImageFileMissing")')
		message %= fileName
		__errorMsg(message)

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