Method for adjusting image display range of a document camera

A method for adjusting an image displaying range of a document camera on an image display device, said method comprising steps of:

• providing a frame buffer;
• receiving a first image frame defined by a first image data and a second image frame defined by a second image data;
• executing an image parallel-displaying function to divide said frame buffer into a first area and a second area where a first portion of said first image data and a first portion of said second image data are loaded, respectively, so as to show a first synthesis image frame having a size equal to the size of said frame buffer and consisting of a first part of said first image frame and a first part of said second image frame with a first-position partition line therebetween;
• and
• executing another image parallel-displaying function to divide said frame buffer into a third area and a fourth area where a second portion of said first image data and a second portion of said second image data are loaded, respectively, so as to show a second synthesis image frame having a size equal to the size of said frame buffer and consisting of a second part of said first image frame and a second part of said second image frame with a second-position partition line therebetween;
• wherein with the movement of a partition line from said first-position partition line to said second-position partition line, image data within a range defined between said first-position partition line and said second-position partition line are changed while image data beyond said range are kept unchanged.