The Stack command stacks images to form a larger image.

The img_list parameter is a list of the images that are to be stacked. The images must have the same number of layers.

The optional dir parameter determines the stacking direction. Allowable values are horizontal and vertical. If horizontal, then the images are stacked horizontally, the first image in the list being the leftmost. If vertical, then the images are stacked vertically, the first image in the list being the topmost. The default is horizontal.

If the input images have different sizes, they are aligned according to the halign or valign options.

halign = left, center, or right

Specifies the horizontal alignment of vertically stacked images. The default is left.

valign = top, center, or bottom

Specifies the vertical alignment of horizontally stacked images. The default is top.