If Image is created directly, add missing core image when loading

[radarhere]

Resolves #7455

Normally, image instances are created with Image.new() or Image.open(). The issue would like to be able to use Image() directly.

The only thing that _new() provides that __init__ doesn't is a core image instance. Pillow allows for im.im to be None, but expects load() to populate it.

Using the fact that __init__ sets _mode to ""

Pillow/src/PIL/Image.py

Lines 483 to 487 in 4ecf1df

	def __init__(self):
	# FIXME: take "new" parameters / other image?
	# FIXME: turn mode and size into delegating properties?
	self.im = None
	self._mode = ""

this PR detects in load() if an image has been directly instantiated, and if so, adds a core image instance with mode 1, as that is the simplest mode.

[homm]

Isn't better restrict creating image instances directly? Is it used anywhere?

[radarhere]

I don't understand why the user in that issue tried to run Image(), but this seemed like a simple solution.

In contrast, preventing users from running Image() but still allowing the following internal uses seemed like it would involve changing some fundamental methods.

Pillow/src/PIL/Image.py

Lines 511 to 512 in 4ecf1df

	def _new(self, im):
	new = Image()

Pillow/src/PIL/Image.py

Lines 2919 to 2937 in 4ecf1df

	if color is None:
	# don't initialize
	return Image()._new(core.new(mode, size))
	if isinstance(color, str):
	# css3-style specifier
	from . import ImageColor
	color = ImageColor.getcolor(color, mode)
	im = Image()
	if mode == "P" and isinstance(color, (list, tuple)) and len(color) in [3, 4]:
	# RGB or RGBA value for a P image
	from . import ImagePalette
	im.palette = ImagePalette.ImagePalette()
	color = im.palette.getcolor(color)
	return im._new(core.fill(mode, size, color))

If the issue is closed, I'm happy to close this as well.

[radarhere]

I've created #7461 as a suggestion for how to restrict creating image instances directly. I think the changes involved are relatively minimal.