How does PA -> P conversion work?

[Yay295]

There is no PA to P function in Convert.c. I tried following the code but I must have missed something because I didn't see where this conversion happens.

[radarhere]

You are correct that PA is not directly converted to P in the C layer at the moment. When support is missing for a direct conversion, the Python layer instead converts first to the base mode, and then to the destination mode.

Pillow/src/PIL/Image.py

Lines 1034 to 1040 in 87ecd01

	try:
	im = self.im.convert(mode, dither)
	except ValueError:
	try:
	# normalize source image and try again
	im = self.im.convert(getmodebase(self.mode))
	im = im.convert(mode, dither)

So it goes PA to RGB, and then RGB to P.

[radarhere]

With #6509, this answer has changed - there is now a pa2p function in Convert.c.