I have just pasted a diagram into my note but many details disappeared due to the dark background, so I wander if I can partially set a white background for showing up the details of that diagram?
I don’t know the details of your situation, but did you paste the PNG image into a note? If so, this is probably caused by a transparent background color for that image and a dark text color. The dark color of Obsidian is showing through and making the diagram difficult to read.
The simple solution, if my guess is correct, is to convert the image(diagram) from PNG to JPG. JPG only handles non-transparent image data, so you can replace the transparent background of the PNG with a white color.
This CSS snippet should works fine. But it always makes the background color of all images white. (I have no idea how to switch the CSS for each image…)
But, as we don’t know the details or have the source png, I think converting the image if it’s only one or two (as snowynest and holroy mentioned) would be the best bet
I didn’t mention html, since I feel it limits the usefullness when going cross platform and inclusion of other markdown within html tags. Although the latter is not very likely to happen using an image…