I am an inexperienced LibreCAD user and struggling with the layer implementation. I am working a CAD file with an image as the bottom layer. The image is a scanned image of the building's layout. Almost all the time when I am adding a new object, it goes below the bottom image. It seems to be impossible to set certain object (the image) as a bottom one permanently.New objects keep get adding below the image. This is rather frustrating.
There is also some zooming error causing the viewpoint to "jump" if I use the sliders.
Plus the color options are missing "black". Scanned images are often white so white/black (white text) is rather poor color option.
No, unfortunately you can't set an object like an image permanently to bottom. Also moving an entity up or down sometimes seems to work not consistently, or it is hard to understand. If you click the image unintentionally it is selected and is highlighted, looking as if on top. A real nuisance is that if you want to select an entity lying on the image by mouse click to edit it, always the image is selected. If the layer with the image is locked, selection of such entities on other layers is blocked completely. But you can select by pulling up a window around them.
Colors: You can use Darkgrey instead of black or a custom self defined nearly black. It might also be suitable to turn the whites of the scan to transparency in a bitmap graphics program. PNG supports transparency.