Hi Janne - the background images displayed in a viewport have to be generated as a texture that is sent to your video card, and it used to be common for many video cards to have a limit on the size of textures that they supported and to also only have a limited amount of space available on them to hold the textures.

So because of that, MoI will automatically resize any background image larger than a certain size.

The default maximum texture size is 2048x2048 - you can alter this setting in the moi.ini file, go to Options > General > Edit .ini file, and find the [View] section, under that section there is a setting:

[View]
MaxTextureSize=2048

Adjust this value to a higher value to raise the maximum size of a background image that MoI will allow before resizing it down.

Note that if you have an older video card with a more limited amount of video memory, moving this limit up is not very good because very large textures will consume a large quantity of video memory and can lead to it being completely exhausted.

What are the pixel dimensions of the very very large bitmap that you are using?

For example a 20000x20000 image will consume 1.5GB of video memory (the texture is completely uncompressed in memory so it can be much larger than the compressed disk size) which would be difficult for a lot of even newer cards to handle.

- Michael