View all files in directory: Click this to have the viewer display in each directory all files with extensions supported by IrfanView. If this is unchecked, you can’t open next/previous file with space/backspace or with the toolbar arrows.
Show hidden files/folders during moving through directory: Enable/disable to show hidden files in the actual directory.
If the end/begin of the folder is reached, loop current folder (during browsing): When you reach the last/first of the images in a directory and browse on to the next/previous image, IrfanView shows you a special browse folder dialog to use another folder/subfolder. Checking this option will suppress the dialog and just go on to the first/last image in the current folder.
Jump always to next image if Arrow or Page keys pressed: Don’t scroll large images, jump always to previous/next image, if you press Arrow/Page keys or roll the mouse wheel.
Use Undo option: Unchecking disables this function of the Edit Menu.
You can set the Options for TXT-files: font, font color (text) and background color.
There is also an option to set the background color which is used for the cut function.
Paste into selection: by default, the pasted image will be stretched to selection, this option allows you to paste the image proportionally.
Import palette: by default, the image colors will be changed 1:1 to colors in the PAL file, this options will search for the best/nearest color in the PAL file.