US5850484A
Expired / Lapsed
US
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Text and image sharpening of JPEG compressed images in the frequency domain
Assignee: HP Inc
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Filing: 1997-09-30
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Granted: 1998-12-15
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Expires: 2017-09-30
Abstract
Abstract The text and image enhancing technique according to the invention is integrated into the decoding or inverse quantization step that is necessarily required by the JPEG standard. The invention integrates the two by using two different quantization tables: a first quantization table (Q E ) for use in quantizing the image data during the compression step and a second quantization table used during the decode or inverse quantization during the decompression process. The second quantization table Q D is related to the first quantization table according to a predetermined function of the energy in a reference image and the energy in a scanned image. The energy of the reference image lost during the scanning process, as represented by the energy in the scanned image, is restored during the decompression process by appropriately scaling the second quantization table according to the predetermined function. The difference between the two tables, in particular the ratio of the two tables, determines the amount of image enhancing that is done in the two steps. By integrating the image enhancing and inverse quantization steps the method does not require any additional computations than already required for the compression and decompression processes.
Inventors
- 👤 Giordano Beretta
- 👤 Vasudev Bhaskaran
- 👤 Konstantinos Konstantinides
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 10:44
CPC Classifications
H; H04; H04N; H04N19/00; H04N19/10; H04N19/102; H04N19/124; H04N19/126; H04N19/60
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
156 words
A machine for transmitting color images comprising: means for rendering a color image into color source image data representing the color image; a compression engine that compresses the source image data into compressed image data, the engine including: a transforming means for converting the source image data into transformed image data, means for storing a first multi-element quantization table (Q E ); a quantizer means for converting the transformed image data into quantized image data in accordance with elements contained in the first quantization table, means for storing a second multi-element quantization table (Q D ) related to but nonidentical to the first quantization table Q E , an entropy encoder means for transforming the quantized image data into the encoded image data using an entropy table; means for encapsulating the encoded image data, the second quantization table, and the entropy table to form an encapsulated data file; and means for transmitting the encapsulated data file.
Claim 2
Dependent Claim
156 words
A machine for transmitting color images comprising: means for rendering a color image into color source image data representing the color image; a compression engine that compresses the source image data into compressed image data, the engine including: a transforming means for converting the source image data into transformed image data, means for storing a first multi-element quantization table (Q E ); a quantizer means for converting the transformed image data into quantized image data in accordance with elements contained in the first quantization table, means for storing a second multi-element quantization table (Q D ) related to but nonidentical to the first quantization table Q E , an entropy encoder means for transforming the quantized image data into the encoded image data using an entropy table; means for encapsulating the encoded image data, the second quantization table, and the entropy table to form an encapsulated data file; and means for transmitting the encapsulated data file.
Claim 3
Dependent Claim
38 words
A machine for transmitting color images according to claim 1 further comprising a scaler for scaling the first quantization table (Q E ) in accordance with a predetermined function to form the second quantization table (Q D ).
Claim 4
Dependent Claim
42 words
A machine for transmitting color images according to claim 1 wherein the second quantization table is related to the first quantization table in accordance with a predetermined function of the energy in a reference image and the energy in a scanned image.
Claim 5
Dependent Claim
65 words
A machine for transmitting color images according to claim 3 wherein the predetermined function is given by the following expression: Q.sub.D =S×Q.sub.E, where S is a scaling matrix having each element S k,l! formed according to the following expression: S k,l!.sup.2 =V* k,l!/V.sub.Y k,l!, where V* is a variance matrix of the reference image and V Y is a variance matrix of the scanned image.
Claim 6
Dependent Claim
59 words
A machine for transmitting color images according to claim 1 wherein the means for rendering a color image into color source image data representing the color image includes: a color scanner; means for gamma correcting the color source image data; and means for transforming the color source image data from a first color space to a second color space.
Claim 7
Dependent Claim
34 words
A machine for transmitting color images according to claim 1 wherein the means for rendering a color image into color source image data representing the color image includes computer software operable on a computer.
Claim 8
Dependent Claim
82 words
A machine for transmitting color images according to claim 1 further comprising: means for receiving an encapsulated data packet; means for decoding the encapsulated data packet to extract a header, received image data, a received quantization table (Q R ), and a received entropy table; a decompression engine that decompresses the received image data into color source image data using the received quantization table and the received entropy table; and means for reproducing a color image from the color source image data.
Claim 9
Dependent Claim
42 words
A machine for transmitting color images according to claim 7 further comprising a scaler for scaling the received quantization table into a scaled quantization table (Q S ), which is used by the decompression engine in lieu of the received quantization table.
Claim 10
Dependent Claim
42 words
A machine for transmitting color images according to claim 8 wherein the scaled quantization table is related to the received quantization table in accordance with a predetermined function of the energy in a reference image and the energy in a scanned image.
Claim 11
Dependent Claim
65 words
A machine for transmitting color images according to claim 9 wherein the predetermined function is given by the following expression: Q.sub.S =S×Q.sub.R, where S is a scaling matrix having each element S k,l! formed according to the following expression: S k,l!.sup.2 =V* k,l!/V.sub.Y k,l!, where V* is a variance matrix of the reference image and V Y is a variance matrix of the scanned image.
Claim 12
Dependent Claim
24 words
A machine for transmitting color images according to claim 10 further comprising means for selectively scaling the received quantization table responsive to the header.
Claim 13
Dependent Claim
44 words
A machine for transmitting color images according to claim 7 wherein the means for reproducing a color image from the color source image data includes computer software operable on a computer for displaying the color image on a computer display associated with the computer.
Claim 14
Dependent Claim
32 words
A machine for transmitting color images according to claim 1 wherein the transforming means includes means for transforming the source image data into transformed image data using the discrete cosine transform (DCT).
Claim 15
Independent Claim
115 words
A method of compressing and transmitting images which produces decompressed images having improved text and image quality, the method comprising: compressing a source image into compressed image data using a first quantization table (Q E ); forming a second quantization table (Q D ), wherein the second quantization table is related to the first quantization table in accordance with a predetermined function of the energy in a reference image and the energy in a scanned image, such that the second quantization table (Q D ) is configured to compensate for image degradation caused by a scanner; transmitting the compressed image data; and decompressing the compressed image data using the second quantization table Q D .
Claim 16
Independent Claim
115 words
A method of compressing and transmitting images which produces decompressed images having improved text and image quality, the method comprising: compressing a source image into compressed image data using a first quantization table (Q E ); forming a second quantization table (Q D ), wherein the second quantization table is related to the first quantization table in accordance with a predetermined function of the energy in a reference image and the energy in a scanned image, such that the second quantization table (Q D ) is configured to compensate for image degradation caused by a scanner; transmitting the compressed image data; and decompressing the compressed image data using the second quantization table Q D .
Claim 17
Dependent Claim
40 words
A method of compressing and transmitting images which produces decompressed images having improved text and image quality according to claim 14 wherein the step forming a second quantization table includes scaling the first quantization in accordance with the predetermined function.
Claim 18
Independent Claim
121 words
A method of compressing and transmitting images which produces decompressed images having improved text and image quality, the method comprising: compressing a source image into compressed image data using a first quantization table (Q E ); forming a second quantization table (Q D ), wherein the second quantization table is related to the first quantization table in accordance with a predetermined function of the energy in a reference image and the energy in a scanned image; transmitting the compressed image data; and decompressing the compressed image data using the second quantization table Q D ; wherein the step of forming a second quantization table includes scaling the first quantization table in accordance with the predetermined function prior to the transmitting step.
Claim 19
Independent Claim
121 words
A method of compressing and transmitting images which produces decompressed images having improved text and image quality, the method comprising: compressing a source image into compressed image data using a first quantization table (Q E ); forming a second quantization table (Q D ), wherein the second quantization table is related to the first quantization table in accordance with a predetermined function of the energy in a reference image and the energy in a scanned image; transmitting the compressed image data; and decompressing the compressed image data using the second quantization table Q D ; wherein the step of forming a second quantization table includes scaling the first quantization table in accordance with the predetermined function prior to the transmitting step.
Claim 20
Dependent Claim
41 words
A method of compressing and transmitting images which produces decompressed images having improved text and image quality according to claim 15 wherein the step scaling the first quantization in accordance with the predetermined function is performed subsequent to the transmitting step.
Claim 21
Dependent Claim
100 words
A method of compressing and transmitting images which produces decompressed images having improved text and image quality according to claim 15 wherein the step forming a second quantization table includes forming a second quantization table (Q D ), where the second quantization table is related to the first quantization table according to the following expression: Q.sub.D =S×Q.sub.E, where S is a scaling matrix having each element S k,l! formed according to the following expression: S k,l!.sup.2 =V* k,l!/V.sub.Y k,l!, where V* is a variance matrix of the reference image and V Y is a variance matrix of the scanned image.
Claim 22
Independent Claim
118 words
A method of compressing and transmitting images which produces decompressed images having improved text and image quality, the method comprising: compressing a source image into compressed image data using a first quantization table (Q E ); forming a second quantization table (Q D ), wherein the second quantization table is related to the first quantization table in accordance with a predetermined function of the energy in a reference image and the energy in a scanned image; transmitting the compressed image data; decompressing the compressed image data using the second quantization table Q D ; encapsulating the second quantization table Q D with the compressed image data to form an encapsulated data file; and transmitting the encapsulated data file.
Claim 23
Independent Claim
118 words
A method of compressing and transmitting images which produces decompressed images having improved text and image quality, the method comprising: compressing a source image into compressed image data using a first quantization table (Q E ); forming a second quantization table (Q D ), wherein the second quantization table is related to the first quantization table in accordance with a predetermined function of the energy in a reference image and the energy in a scanned image; transmitting the compressed image data; decompressing the compressed image data using the second quantization table Q D ; encapsulating the second quantization table Q D with the compressed image data to form an encapsulated data file; and transmitting the encapsulated data file.
Claim 24
Dependent Claim
43 words
A method of compressing and transmitting images having improved text and image quality according to claim 14 wherein the step of forming a second quantization table (Q D ) includes: selecting a target image; and rendering the target image into an image file.
Claim 25
Dependent Claim
43 words
A method of compressing and transmitting images having improved text and image quality according to claim 20 wherein the step of selecting a target image includes selecting a target image having critical image elements that are critical to the quality of the image.
Claim 26
Dependent Claim
32 words
A method of compressing and transmitting images having improved text and image quality according to claim 20 wherein the step of selecting a target image includes selecting a target image having text.
Claim 27
Dependent Claim
36 words
A method of compressing and transmitting images having improved text and image quality according to claim 20 wherein the step of selecting a target image includes selecting a target image having text with a serif font.
Claim 28
Independent Claim
101 words
A method of forming a quantization table for use in compressing images in accordance with the JPEG compression standard, the method comprising: selecting a first quantization table (Q E ); and forming a second quantization table (Q D ), where the second quantization table is related to the first quantization table according to the following expression: Q.sub.D =S×Q.sub.E, where S is a scaling matrix having each element S k,l! formed according to the following expression: S k,l!.sup.2 =V* k,l!/V.sub.Y k,l!, where V* is a variance matrix of a reference image and V Y is a variance matrix of a scanned image.
Claim 29
Independent Claim
101 words
A method of forming a quantization table for use in compressing images in accordance with the JPEG compression standard, the method comprising: selecting a first quantization table (Q E ); and forming a second quantization table (Q D ), where the second quantization table is related to the first quantization table according to the following expression: Q.sub.D =S×Q.sub.E, where S is a scaling matrix having each element S k,l! formed according to the following expression: S k,l!.sup.2 =V* k,l!/V.sub.Y k,l!, where V* is a variance matrix of a reference image and V Y is a variance matrix of a scanned image.
Claim 30
Dependent Claim
47 words
A method of forming a quantization table according to claim 24 wherein the step of forming a second quantization table (Q D ) includes: selecting the reference image; rendering the reference image into reference image data; and computing the variance matrix V* for the reference image data.
Claim 31
Dependent Claim
45 words
A method of forming a quantization table according to claim 25 wherein the step of forming a second quantization table (Q D ) includes: scanning the scanned image to produce scanned image data; and computing the variance matrix V Y for the scanned image data.
Claim 32
Dependent Claim
29 words
A method of forming a quantization table according to claim 26 wherein the step of scanning the scanned image to produce scanned image data includes scanning the reference image.
Claim 33
Independent Claim
154 words
A method of improving text and image quality of compressed images that are compressed using the JPEG compression standard, the method comprising: selecting a reference image; determining the energy content of the reference image; selecting a scanned image; determining the energy content of the scanned image; selecting a first quantization table (Q E ); scaling the first quantization table (Q E ) to form a second quantization table (Q D ) according to the ratio of the energy in the reference image to the energy content of the scanned image, such that the second quantization table (Q D ) is configured to compensate for image degradation caused by a scanner; compressing a source image in accordance with the JPEG standard using the first quantization table (Q E ); and decompressing the source image in accordance with the JPEG standard using the second quantization table Q D whereby the decompressed image has improved image quality.
Claim 34
Independent Claim
154 words
A method of improving text and image quality of compressed images that are compressed using the JPEG compression standard, the method comprising: selecting a reference image; determining the energy content of the reference image; selecting a scanned image; determining the energy content of the scanned image; selecting a first quantization table (Q E ); scaling the first quantization table (Q E ) to form a second quantization table (Q D ) according to the ratio of the energy in the reference image to the energy content of the scanned image, such that the second quantization table (Q D ) is configured to compensate for image degradation caused by a scanner; compressing a source image in accordance with the JPEG standard using the first quantization table (Q E ); and decompressing the source image in accordance with the JPEG standard using the second quantization table Q D whereby the decompressed image has improved image quality.
Claim 35
Dependent Claim
34 words
A method of improving text and image quality according to claim 28 wherein the step of determining the energy content of the reference image includes determining a variance matrix (V*) of the reference image.
Claim 36
Dependent Claim
36 words
A method of improving text and image quality according to claim 29 wherein the step of determining the energy content of the scanned image includes determining a variance matrix (V Y ) of the scanned image.
Claim 37
Dependent Claim
127 words
A method of improving text and image quality according to claim 30 wherein the step of scaling the first quantization table (Q E ) to form a second quantization table (Q D ) according to the ratio of the energy in the reference image to the energy content of the scanned image includes: determining a scaling matrix (S), where each element S k,l! being formed according to the following expression: S k,l!.sup.2 =V* k,l!/V.sub.Y k,l!, where V* k,l! is a corresponding element in the variance matrix V* and V Y k,l! is the corresponding element in the variance matrix V Y ; and scaling the first quantization table (Q E ) to form a second quantization table (Q D ) according to the following expression: Q.sub.D =S×Q.sub.E.
Claim 38
Independent Claim
160 words
A method of improving text and image quality of compressed images that are compressed using the JPEG compression standard, the method comprising: selecting a reference image; determining the energy content of the reference image; selecting a scanned image; determining the energy content of the scanned image; selecting a first quantization table (Q E ); scaling the first quantization table (Q E ) to form a second quantization table (Q D ) according to the ratio of the energy in the reference image to the energy content of the scanned image; compressing a source image in accordance with the JPEG standard using the first quantization table (Q E ); decompressing the source image in accordance with the JPEG standard using the second quantization table Q D whereby the decompressed image has improved image quality; encapsulating the second quantization table (Q D ) with the compressed image to form a JPEG file; and transmitting the JPEG file over a limited bandwidth channel.
Claim 39
Independent Claim
160 words
A method of improving text and image quality of compressed images that are compressed using the JPEG compression standard, the method comprising: selecting a reference image; determining the energy content of the reference image; selecting a scanned image; determining the energy content of the scanned image; selecting a first quantization table (Q E ); scaling the first quantization table (Q E ) to form a second quantization table (Q D ) according to the ratio of the energy in the reference image to the energy content of the scanned image; compressing a source image in accordance with the JPEG standard using the first quantization table (Q E ); decompressing the source image in accordance with the JPEG standard using the second quantization table Q D whereby the decompressed image has improved image quality; encapsulating the second quantization table (Q D ) with the compressed image to form a JPEG file; and transmitting the JPEG file over a limited bandwidth channel.
Claim 40
Dependent Claim
76 words
A method of improving text and image quality according to claim 28 further comprising: selecting a plurality of reference images; determining the energy content of each reference image; averaging the energy content of the plurality of reference images; and scaling the first quantization table (Q E ) to form a second quantization table (Q D ) according to the ratio of the average energy in the reference images to the energy content of the scanned image.
Claim 41
Dependent Claim
37 words
A method of improving text and image quality according to claim 33 wherein the step of selecting a plurality of reference images includes selecting a plurality of reference images each reference image having a different graphical content.
Claim 42
Dependent Claim
76 words
A method of improving text and image quality according to claim 28 further comprising: selecting a plurality of scanned images; determining the energy content of each scanned image; averaging the energy content of the plurality of scanned images; and scaling the first quantization table (Q E ) to form a second quantization table (Q D ) according to the ratio of the energy in the reference image to the average energy content of the scanned images.
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