Image processor for and method of performing tonal transformation on image data

• US 7,418,138 B2
• Filed: 12/15/2004
• Issued: 08/26/2008
• Est. Priority Date: 12/15/2004
• Status: Active Grant

• Current Assignee: Lexmark International Incorporated (Ninestar Corporation)
• Original Assignee: Lexmark International Incorporated (Ninestar Corporation)
• Inventors: Ahmed, Mohamed N.
• Primary Examiner(s): Alavi; Amir
• Application Number:
  US11/013,523
• Publication Number:
  US 20060126931A1
• Time in Patent Office: 1,350 Days
• Field of Search: 382/162, 382/164, 382/167, 382/172, 382/173, 382/181, 382/190, 382/195, 382/206, 382/254, 382/272, 382/305, 358/1.9, 358/515, 358/518, 358/520, 358/523, 358/524, 358/530, 345/549, 345/581, 345/589, 345/591, 345/601, 348/674, 348/E5.074
• US Class Current: 382/190
• CPC Class Codes: H04N 1/40062 Discrimination between different image types, e.g. two-tone, continuous tone
• CPC Class Codes: H04N 1/4072 dependent on the contents of the original

Abstract

A method of performing tonal transform on image data. The method includes extracting a portion of the image data, assigning one of a plurality of labels to the extracted portion, performing a first tonal transformation on the extracted portion if a first label is assigned to the extracted portion, and performing a second tonal transformation on the extracted portion if a second label is assigned to the extracted portion. The method can be performed, for example, with an image processor comprising a memory that stores the image data and a processor coupled to the memory.

Claims

1. A method of performing tonal transformation on image data, the method comprising:

extracting a plurality of portions of the image data;

assigning one of a plurality of labels to each of the plurality of extracted portions, the plurality of labels comprising a first label and a second label;

performing a first tonal transformation on the extracted portion assigned the first label; and

performing a second tonal transformation on the extracted portion assigned the second label.

2. The method as set forth in claim 1, further comprising:

obtaining an image file comprising the image data.

3. The method as set forth in claim 2, wherein the image data comprises a plurality of intensities of a color tone.

4. The method as set forth in claim 1, wherein the image data represents an image and wherein the method further comprises acquiring the image data with one of the group consisting of a scanner, a digital camera, a facsimile machine, and a digital video camera.

5. The method as set forth in claim 1, further comprising:

downsampling the image data.

6. The method as set forth in claim 1, further comprising:

establishing a threshold value for the image data, and

wherein extracting one of the plurality of portions of the image data comprises

selecting an image datum having an intensity value with a relation to the threshold value; and

identifying the image data having intensity values with the same relation to the threshold value as the selected image datum and being connected to the selected image datum.

7. The method as set forth in claim 6, wherein the relation is the intensity value being greater than the threshold value.

8. The method as set forth in claim 6, wherein establishing a threshold value comprises retrieving the threshold value from memory.

9. The method as set forth in claim 6, wherein establishing a threshold value comprises performing an adaptive thresholding technique to determine the threshold value.

10. The method as set forth in claim 9, wherein performing an adaptive thresholding technique comprises:

setting an initial threshold value;

segmenting the image data into a plurality of groups;

computing a mean value for each of the plurality of groups; and

computing a new threshold value based on the mean values.

11. The method as set forth in claim 10 wherein performing an adaptive thresholding technique further comprises repeating the segmenting and computing acts.

12. The method as set forth in claim 10 wherein segmenting the image data comprises:

segmenting a first image datum into a first of the plurality of groups when a value of the first image datum is greater than the initial threshold value, and

segmenting a second image datum into a second of the plurality of groups when the value of the second image datum is less than the initial threshold value.

13. The method as set forth in claim 1, wherein assigning one of a plurality of labels is based on a characteristic of the extracted portion.

14. The method as set forth in claim 13, wherein the characteristic is the aspect ratio of the extracted portion.

15. The method as set forth in claim 13, wherein the characteristic is the size of the extracted portion.

16. The method as set forth in claim 1, wherein the first tonal transformation is a gamma correction using a first gamma value and the second tonal transformation is a gamma correction using a second gamma value.

17. An image processor for performing tonal transformation on image data, the image processor comprising:

a memory comprising the image data; and

a processor configured to extract a plurality of portions of the image data, assign one of a plurality of labels to each of the plurality of extracted portions, the plurality of labels comprising a first label and a second label, perform a first tonal transformation on the extracted portions assigned the first label, and perform a second tonal transformation on the extracted portions assigned the second label.

18. The image processor as set forth in claim 17, wherein the processor is implemented via an application specific integrated circuit.

19. The image processor as set forth in claim 17, wherein the processor is implemented via a computer.

20. The image processor as set forth in claim 17, wherein the processor is configured to perform the first tonal transformation on the extracted portion by performing a first gamma correction using a first gamma value on the extracted portion, and wherein the image processor is configured to perform the second tonal transformation by performing a second gamma correction using a second gamma value on the extracted portion.

21. A method of performing tonal transformation on image data of an image file, the method comprising:

dividing at least a portion of the image data into at least two subgroups of image data based on an attribute of the image data, the at least two subgroups of image data comprising a first subgroup of image data and a second subgroup of image data;

performing a first tonal transformation on the first subgroup of image data; and

performing a second tonal transformation on the second subgroup of image data, the second tonal transformation being different from the first tonal transformation.

22. The method as set forth in claim 21, wherein the attribute comprises an intensity value for each image datum.

23. The method as set forth in claim 22, wherein dividing at least a portion of the image data into the first subgroup comprises:

selecting an image datum having an intensity value with a relation to a threshold value, and

identifying image data having intensity values with the same relation to the threshold value as the selected image datum and being connected to the selected image datum; and

wherein performing a first tonal transformation on the first subgroup comprises performing a first tonal transformation on the selected and identified image data.

24. The method as set forth in claim 23, wherein the relation is the intensity value being greater than the threshold value.

25. The method as set forth in claim 23, wherein the threshold value is determined by performing an adaptive thresholding technique comprising:

setting an initial threshold value;

segmenting the image data into a plurality of groups;

computing a mean value for each of the plurality of groups;

computing a new threshold value based on the mean values; and

repeating the segmenting and computing acts.

26. The method as set forth in claim 21, further comprising:

assigning one of a plurality of labels to each of the at least two subgroups of image data, the plurality of labels comprising a first label and a second label; and

wherein performing a first tonal transformation and performing a second tonal transformation is based on the respective label assigned to the first and second subgroups.

27. The method as set forth in claim 21, wherein the first tonal transformation is a gamma correction using a first gamma value and the second tonal transformation is a gamma correction using a second gamma value.