The (blue) button opens a small window in which the user can drag and drop the selection that must be used in the photo mosaic. The (orange) checkbox on the left must be ticked to activate the multiple mask option. If un-checked only the current mask in the mask selection box will be used. Don't forget to also indicate if the mask and/or overlay must be applied (the two checkboxes above the mask selection box).

In the picture above the multi-mask selection window is shown. On the left the whole range of available masks is shown. On the right the selection that must be used. To add masks to the selection you need to drag-and-drop the thumbnail pictures from left to right, and drag-and-drops from right to left to remove the mask from the selection. There must always be one mask available (that mask can't be removed). The sequence of masks is not important. The user can add several same masks to the selection. The more same masks, the higher the probability it will be used.

Alpha or 32 bit
Make your choice of mask selections: alpha masks are greyscale masks (file type is .jpg and are starting with 'a_' and 'b_'), 32 bit are colour or greyscale masks with an additional transparency channel (file types are .bmp and .png and is starting with 'o32_'). If the selection is changed the mask selection on the right is lost.

Cancel and OK
When the 'Cancel' button is pressed the mask selection is not updated. When pressing 'OK' the mask selection is saved.