Rearrange ImagingPoint code

[radarhere]

I find

Pillow/src/libImaging/Point.c

Lines 147 to 153 in 852d834

	if (imIn->type != IMAGING_TYPE_UINT8) {
	if (imIn->type != IMAGING_TYPE_INT32 || mode != IMAGING_MODE_L) {
	goto mode_mismatch;
	}
	} else if (!imIn->image8 && imIn->mode != mode) {
	goto mode_mismatch;
	}

rather confusing to read. Everything is using a negative condition.

Here's my suggestion instead.

if (imIn->type == IMAGING_TYPE_UINT8) {
	if (imIn->mode != mode && !imIn->image8) {
		goto mode_mismatch;
	}
} else if (imIn->type == IMAGING_TYPE_INT32) {
	if (mode != IMAGING_MODE_L) {
		// I images can only be used with L output mode
		goto mode_mismatch;
	}
} else {
	// Reject F modes and modes based on I;16
	goto mode_mismatch;
}

The I images comment is mirroring

Pillow/src/PIL/Image.py

Lines 2023 to 2025 in 852d834

	:param mode: Output mode (default is same as input). This can only be used if
	the source image has mode "L" or "P", and the output has mode "1" or the
	source image mode is "I" and the output mode is "L".