Handy Viewer supports the following hot-keys:
"Ctrl+O" - show open dialog;
"Ctrl+N" - show Create New Image dialog;
"Ctrl+S" - show "Save to Original Folder..." dialog. The original directory of the current file is used by default;
"Ctrl+Alt+S" - show "Save to Recent Folder..." dialog. The recent output directory is used by default;
"Ctrl+1" - open current image file with external editor № 1;
"Ctrl+2" - open current image file with external editor № 1;
"Ctrl+3" - open current image file with external editor № 1;
"Ctrl+Delete" - delete current file from the drive;
"F2" - rename file;
"F3" - move file to other destination;
"Ctrl+W" - set current image as wallpaper on desktop;
"Ctrl+X" - cut the selected portion of the image and put to clipboard;
"Ctrl+C" - copy the selected portion or the whole image to clipboard;
"Ctrl+V" - paste image content from clipboard to Handy Viewer;
"Ctrl+Z" - undo the last change.
"Ctrl+Y" - redo the change.
"F11" or "Enter" - enter/exit full screen;
"Exit" - exit full screen or slideshow;
"Right Arrow" or "Space" - open next image in the folder;
"Left Arrow" - open previous image in the folder;
"+" - zoom in;
"-" - zoom out;
"Ctrl+F" - fit image to window;
"R" - rotate image clockwise (to the right);
"L" - rotate image counter clockwise (to the left);
"Ctrl+R" - show "Image Resize" window;
"Ctrl+A" - show "Adjust Colors" window;
"Ctrl+G" - convert current image to gray-scale;
"Ctrl+I" - open Information window: general, EXIF, IPTC information;
"Ctrl+E" - show Effects Browser;
"Ctrl+P" - show Painting Tools;