Presentation system and display device for use in the presentation system

An image projecting method executed by a display apparatus, comprising:

• receiving an input image from an external apparatus;
• receiving string data from the external apparatus;
• generating a message display image based on the string data received from the external apparatus;
• and
• receiving selection information from the external apparatus, the selection information for switching whether the input image and the message display image are synthesized to be superimposed on each other or the input image and the message display image are synthesized not to be superimposed on each other is received from the external apparatus,
• generating a synthetic image by synthesizing the input image received from the external apparatus with the message display image based on the selection information, and
• projecting the synthetic image on to a projection surface,
• wherein a type of the synthetic image among two types of synthetic images is changed based on the selection information, the two types of synthetic images are:
• a first type of the synthetic image in which the input image and the message display image are synthesized to be superimposed on each other, and in which the message display image is arranged inside of a display region of the input image;
• and
• a second type of the synthetic image in which the input image and the message display image are synthesized not to be superimposed on each other, and in which the message display image is arranged at a position at one side end of the synthetic image and outside of a display region of the input image, and
• wherein when the input image and the message display image are synthesized not to be superimposed on each other, the synthetic image is generated so that the message display image is displayed on a portion generated due to a difference between an aspect ratio of a range in which the display apparatus is able to optically project an image to display the image and an aspect ratio of the input image in the range.