This is a pretty simple conversion script to get .ptf texture files into a format that ImageMagick could further process into any desired output formats.

ptf2pam.py

"""Copyright 2019 Uradamus

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of the Software,
and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
"""

from sys import argv

DEBUG = True

def translate_565(pixel):
	blue = int((pixel % 32) * 8.225806451612904 + 0.5)
	green = int(((pixel >> 5) % 64) * 4.0476190476190474 + 0.5)
	red = int((pixel >> 11) * 8.225806451612904 + 0.5)
	
	return (red, green, blue)

def translate_4444(pixel):
	blue = (pixel % 16) * 17
	green = ((pixel >> 4) % 16) * 17
	red = ((pixel >> 8) % 16) * 17
	alpha = (pixel >> 12) * 17
	
	return (red, green, blue, alpha)


### Open file and populate the input bytearray

with open(argv[1], 'rb') as f:
	input = bytearray(f.read())


### Capture the header portion of the input.

# ptf_header has 1 str for each of the 7 lines in the header.
ptf_header = ['', '', '', '', '', '', '']
# index keeps track of which header str we are concatenating to.
index = 0
# count keeps track of how many characters are in the header,
# so we know where the body starts.
count = 0

for byte in input:
	count += 1
	
	# 10 is the ASCII value for the newline character,
	# which is the delimiter found at the end of each
	# section of the header.
	if byte != 10:
		ptf_header[index] += str(chr(byte))
	else:
		# move to next section of header when \n is encountered.
		if index < 6:
			index += 1
		# until the end of the header.
		else:
			break

if DEBUG:
	print('PTF Header:', ptf_header)


### Parse ptf_header to create pam_header.

color_format = ptf_header[2][8:]
depth = 0
tuple_type = ''

if color_format == 'RGB565':
	depth = 3
	tuple_type = 'RGB'
elif color_format == 'ARGB4444':
	depth = 4
	tuple_type = 'RGB_ALPHA'
else:
	print('Unknown Color Format:', color_format)
	quit()

width = int(ptf_header[3][7:])
height = int(ptf_header[4][8:])
pam_header = 'P7\nWIDTH ' + str(width) + '\nHEIGHT ' + str(height) + '\nDEPTH ' + str(depth) + '\nMAXVAL 255\nTUPLTYPE ' + tuple_type + '\nENDHDR\n'

if DEBUG:
	print('PAM Header:', pam_header)


### Convert pixel data from input.

pixel_buffer = list()
marker = count

for row in range(height):
	pixel_buffer.append(bytearray(width * depth))
	column_index = 0
	for pixel in range(width):
		if color_format == 'RGB565':
			pixel = translate_565((input[marker] << 8) + input[marker + 1])
		elif color_format == 'ARGB4444':
			pixel = translate_4444((input[marker] << 8) + input[marker + 1])
		marker += 2
		for component in pixel:
			pixel_buffer[row][column_index] = component
			column_index += 1

#if DEBUG:
#	print(pixel_buffer)


### Output

output = argv[1][:-3] + 'pam'
with open(output, 'wb') as f:
	f.write(bytearray(pam_header, 'ascii'))
	for row in range(height):
		f.write(pixel_buffer[row])

if DEBUG:
	print(output)