Some (rasterised) PDFs don't invert properly

[adil192]

Describe the bug

Some PDFs invert to a completely black rectangle. Other PDFs invert weirdly -- showing outlines of letters and not their fill.

To reproduce

1. Import a PDF with text in it
2. Turn on dark mode and inversion
3. See result like screenshots

Expected behavior

Invert normally

Saber version

v0.12.0 (12010)

Device

• Device: Google Pixel 6 Pro
• OS: Android 13

Anything else?

• May be solved by Invert image directly rather than a snapshot #627
• Import/export PDFs losslessly #432 might cover up this issue but it will remain for PDFs imported before Import/export PDFs losslessly #432 is completed

[adil192]

Both of these problems seem to be fixed in v0.12.9, maybe because of upstream flutter fixes or because of 8fe64c2.

[adil192]

Nope they're only fixed on my Galaxy Tab S7 (OneUI 5.1/Android 13) but not my Pixel 6 (Android 13)

[adil192]

Testing image:

(Uninverted)	Before	After