Method and system for copy protection of on-screen display of text

• US 5,905,505 A
• Filed: 09/13/1996
• Issued: 05/18/1999
• Est. Priority Date: 05/13/1996
• Status: Expired due to Fees

• Current Assignee: TTI Inventions C LLC (Intellectual Ventures LLC)
• Original Assignee: Bell Communications Research, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Lesk, Michael E.
• Primary Examiner(s): Nguyen, Phu K.
• Application Number:
  US08/716,677
• Time in Patent Office: 977 Days
• Field of Search: 345/435, 345/113, 345/114, 345/115, 345/116, 345/117
• US Class Current: 345/630
• CPC Class Codes: G06F 21/84 output devices, e.g. displays or monitors
• CPC Class Codes: G06F 2221/032 Protect output to user by software means

Abstract

Method and system for preventing copying of textual images during display on a screen. The method includes randomly adding bits to the bitmapped background of the textual image to produce two random bitmapped textual images. The random bitmapped images are then alternately displayed on the screen so that the instantaneous display of the on screen textual images is unreadable. By a second method, the bits that form the bitmapped image of the text bits are randomly modified to produce a pair of random bitmapped texts. The random bit mapped text pairs are then alternately flickered on the display screen. Again, by this second method, the instantaneous display of the on screen textual images is unreadable. Although in both cases the instantaneous display is unreadable, the human eye averages the two different bitmapped images as they alternate on screen so that the text is human readable.

Claims

1. A medium for storing a program for displaying a selected image, said program:

generating a first background random bitmap;

generating a second background random bitmap;

adding said first background to said selected image to create a first combined image;

adding said second background to said selected image to create a second combined image; and

displaying, alternately and in succession on a display device, said first combined image and said second combined image such that said selected image is recognizable to the human eye.

2. The medium of claim 1 wherein said program further successively repositions said combined images relative to the screen of said display device.

3. The medium of claim 1 wherein said medium is a magnetic storage medium.

4. The medium of claim 1 wherein said medium is an optical disk.

5. A method for preventing copying of an on-screen textual image having a bitmap background and bitmap text, the bitmap using two contrasting bits to represent the textual image, said method comprising the steps of:

adding random bits to the background of the textual image to produce a first bitmapped textual image;

adding random bits to the background of the textual image to produce a second bitmapped textual image; and

alternately displaying said first bitmapped textual image and said second bitmapped image on the screen so that the instantaneous on screen image is unreadable.

6. The method according to claim 5 wherein said second bitmapped image is created by inverting said first bitmapped image.

7. The method according to claim 5 further comprising the step of wobbling said alternately displayed bitmapped textual images up and down on the screen.

8. The method according to claim 5 further comprising the step of encrypting said alternately displayed textual images before display to the user.

9. The method according to claim 5 wherein the textual image is high contrast art.

10. The method according to claim 5 wherein each of said background adding steps comprises the substeps of:

randomly adding dark bits to a clear background bitmap image to produce a random bitmapped background; and

logically OR-ing said random bitmapped background with the bitmapped text to produce said first and second bitmapped textual images.

11. The method according to claim 10 wherein bits from the bitmapped text are randomly removed to form random bitmapped text having half the textual information.

12. The method according to claim 10 wherein only one out of every four bits added is dark.

13. The method according to claim 12 wherein the dark bits are black and the clear background image is white.

14. The method according to claim 12 wherein the dark bits are red and the clear background image is green.

15. A method for preventing copying of an on-screen textual image having bitmapped text, the bitmap using a dark bit and a clear bit to represent the textual image, said method comprising the steps of:

randomly modifying the bitmapped text to form a first bitmapped textual image;

randomly modifying the bitmapped text to form a second bitmapped textual image;

alternately flickering said second and first bitmapped textual images on a bitmapped background on the screen so that the instantaneous on screen is display unreadable.

16. The method according to claim 15 wherein said random modification step further comprises the substep of randomly removing dark bits from the text bitmapped image to produce said first and second bitmapped textual images having half the textual information.

17. The method according to claim 16 wherein the bitmapped background comprises a clear bitmapped image.

18. The method according to claim 15 wherein said flickering step includes the substep of randomly adding dark bits to a clear background bitmap image to produce the bitmapped background.

19. The method according to claim 18 further comprising the step of wobbling said alternately flickered textual images up and down on the screen.

20. The method according to claim 18 wherein only one out of every four bits added is dark.

21. A system for preventing copying of on screen bitmapped images having bitmapped text and a bitmapped background, said system comprising:

a display device;

a communications network; and

a server having pairs of the bitmapped images that are to be displayed on said display device, each of said bitmapped image pairs being alternately transmitted by said server over said communications network to said display device.

22. A system according to claim 21 wherein said server further includes:

means for randomly adding bits to the background of the bitmapped image to produce a random background bitmap; and

means for logically OR-ing said random background bitmap with the bitmapped text.

23. A system according to claim 22 wherein said server further includes:

means for randomly removing bits from the bitmapped text to produce a random text bitmap; and

means for alternately flickering random text bitmap pairs against a bitmap background.

24. A system according to claim 23 wherein said server further includes means for slowly wobbling the text displayed to the user'"'"'s screen up and down and encrypting the text displayed at the user.