Black white image scaling having print density control and polarity detection

• US 7,830,552 B2
• Filed: 04/15/2005
• Issued: 11/09/2010
• Est. Priority Date: 04/15/2005
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Prakash, Ravinder
• Primary Examiner(s): Coles; Edward L
• Assistant Examiner(s): Cato; Miya J
• Application Number:
  US11/107,217
• Publication Number:
  US 20060232794A1
• Time in Patent Office: 2,034 Days
• Field of Search: 358/2.99, 358/1.2, 382/232, 382/233
• US Class Current: 358/2.99
• CPC Class Codes: G06T 3/4023 based on decimating pixels or lines of pixels; based on inserting pixels or lines of pixels
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution

Abstract

A scaling system and method for scaling a bitonal image that has print density control. A system for scaling a bitonal image is provide that includes: a polarity detection system for detecting a polarity of the bitonal image; a pixel reduction system that generates a scaled image by reducing pixel pairs down to single scaled pixels by selectively applying either a normal or reverse set of pixel reduction rules, wherein an applied set of pixel reduction rules is determined based on a detected polarity; and a line density control system that allows the scaled image to be made lighter or darker by changing the applied set of pixel reduction rules.

Claims

1. A scaling system for scaling a bitonal image, comprising:

at least one computer hardware device;

a polarity detection system for detecting a polarity of the bitonal image;

a pixel reduction system that generates a scaled image by reducing a plurality of two pixel sets to a plurality of single pixels by selectively applying either a normal or reverse set of pixel reduction rules, wherein an applied set of pixel reduction rules is determined based on a detected polarity, wherein the applied set of pixel reduction rules map an input comprised of four pixel values to an output comprised of one pixel value, wherein the four pixel values include two values of a two pixel set being reduced to a single pixel and two values of two pixels that flank the two pixel set being reduced to a single pixel; and

a line density control system that allows the scaled image to be made lighter or darker by changing the applied set of pixel reduction rules.

2. The scaling system of claim 1, wherein the applied set of pixel reduction rules are incorporated into a look-up table.

3. The scaling system of claim 1, wherein the applied set of pixel reduction rules provide for sixteen possible values for the input ranging from binary 0000 to 1111, and two possible values for the output comprising 0 and 1.

4. The scaling system of claim 3, wherein the input values 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110 and 1111 map to outputs 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, respectively for a normal line density setting.

5. The scaling system of claim 4, wherein the line density control system sets the outputs associated with inputs 0011 and 0101 to 0 to achieve a darker image for a normal polarity image, and sets the outputs associated with inputs 1100 and 1010 to 1 to achieve a darker image for a reverse polarity image.

6. The scaling system of claim 4, wherein the line density control system sets the outputs associated with inputs 1010 and 1100 to 1 to achieve a lighter image for a normal polarity image, and sets the outputs associated with inputs 0101 and 0011 to 0 to achieve a lighter image for a reverse polarity image.

7. The scaling system of claim 1, wherein the bitonal image comprises a black white image.

8. The scaling system of claim 1, wherein the polarity detection system examines photometric information in the bitonal image to detect polarity.

9. The scaling system of claim 1, further comprising an automated density selection system that automatically determines whether the scaled image should be made lighter or darker.

10. The scaling system of claim 9, wherein the automated density selection system analyzes data selected from the group consisting of:

stroke width, font size, and print density.

11. A computer readable medium storing a program product for scaling a bitonal image, comprising computer readable program code for performing the steps of:

detecting a polarity of the bitonal image;

generating a scaled image by reducing a plurality of two pixel sets to a plurality of single pixels by selectively applying either a normal or reverse set of pixel reduction rules, wherein an applied set of pixel reduction rules is determined based on a detected polarity, wherein the applied set of pixel reduction rules map an input comprised of four pixel values to an output comprised of one pixel value, wherein the four pixel values include two values of a two pixel set being reduced to a single pixel and two values of two pixels that flank the two pixel set being reduced to a single pixel;

changing the applied set of pixel reduction rules to allow the scaled image to be made lighter or darker; and

retrieving the scaled image on a device for displaying or printing the scaled image.

12. The computer readable medium of claim 11, wherein the applied set of pixel reduction rules are incorporated into a look-up table.

13. The computer readable medium of claim 11, wherein the applied set of pixel reduction rules for a normal line density setting provide for sixteen possible values for the input ranging from binary 0000 to 1111, and two possible values for the output of 0 and 1, and wherein the input values 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110 and 1111 map to outputs 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, respectively.

14. The computer readable medium of claim 13, wherein said changing the applied set of pixel reduction rules sets the outputs associated with inputs 0011 and 0101 to 0 to achieve a darker image for a normal polarity image, and sets the outputs associated with inputs 1100 and 1010 to 1 to achieve a darker image for a reverse polarity image.

15. The computer readable medium of claim 13, wherein said changing the applied set of pixel reduction rules sets the outputs associated with inputs 1010 and 1100 to 1 to achieve a lighter image for a normal polarity image, and sets the outputs associated with inputs 0101 and 0011 to 0 to achieve a lighter image for a reverse polarity image.

16. The computer readable medium of claim 11, wherein the detecting polarity examines photometric information in a header of the bitonal image.

17. The computer readable medium of claim 11, further comprising automatically determining whether the scaled image should be made lighter or darker.

18. The computer readable medium of claim 17, wherein the determining analyzes data selected from the group consisting of:

stroke width, font size and print density.

19. A method for scaling a bitonal image, comprising:

selecting a line density setting;

determining a polarity of the bitonal image;

selecting a set of pixel reduction rules based on the selected line density setting and on the polarity of the bitonal image, wherein the set of pixel reduction rules map an input comprised of four pixel values to an output comprised of one pixel value, wherein the four pixel values include two values of a two pixel set being reduced to a single pixel and two values of two pixels that flank the two pixel set being reduced to a single pixel;

generating a scaled image by reducing a plurality of two pixel sets to a plurality of single pixels based on the selected set of pixel reduction rules; and

retrieving the scaled image on a device for displaying or printing the scaled image.

20. The method of claim 19, wherein the step of selecting a line density setting is done automatically by analyzing data on the bitonal image, wherein the data is selected from the group consisting of:

stroke width, font size, and print density.

21. The method of claim 19, wherein the line density setting is selected from the group consisting of:

light, normal and dark.

22. The method of claim 19, wherein the set of pixel reduction rules for a normal line density setting provide for sixteen possible values for the input ranging from binary 0000 to 1111, and two possible values for the output of 0 and 1, and wherein the input values 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110 and 1111 map to outputs 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, respectively.

23. The method of claim 22, wherein the set of pixel reduction rules sets the outputs associated with inputs 0011 and 0101 to 0 to achieve a darker image for a normal polarity image, and sets the outputs associated with inputs 1100 and 1010 to 1 to achieve a darker image for a reverse polarity image.

24. The method of claim 22, wherein the set of pixel reduction rules sets the outputs associated with inputs 1010 and 1100 to 1 to achieve a lighter image for a normal polarity image, and sets the outputs associated with inputs 0101 and 0011 to 0 to achieve a lighter image for a reverse polarity image.

25. The method of claim 19, wherein the step of determining the polarity include examining photometric information in a header of the bitonal image.

26. The method of claim 19, comprising the further step of encoding the scaled image with a CCITT-G4 encoder.

27. A method for deploying an application that scales bitonal images, comprising:

providing at least one computer hardware device for performing the steps of;

detect a polarity of the bitonal image;

generate a scaled image by reducing a plurality of two pixel sets to a plurality of single pixels by selectively applying either a normal or reverse set of pixel reduction rules, wherein an applied set of pixel reduction rules is determined based on a detected polarity, wherein the applied set of pixel reduction rules map an input comprised of four pixel values to an output comprised of one pixel value, wherein the four pixel values include two values of a two pixel set being reduced to a single pixel and two values of two pixels that flank the two pixel set being reduced to a single pixel;

allow the scaled image to be made lighter or darker by changing the applied set of pixel reduction rules; and

retrieve the scaled image on a device for displaying or printing the scaled image.