Image processing method and image processing apparatus

An image processing method includes receiving an image data including a first pixel, a second pixel and a third pixel, the second pixel being between the first pixel and the third pixel; calculating a difference between two initial chrominance values of the first pixel and two initial chrominance values of the second pixel to determine a first difference, and calculating a difference between the two initial chrominance values of the second pixel and two initial chrominance values of the third pixel to determine a second difference; comparing the first difference with the second difference to select either the first pixel or the third pixel as a target pixel; and determining two adjusted chrominance values of the second pixel according to at least two initial chrominance values of the target pixel.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims priority from Taiwan Patent Application No. 098133141, filed on Sep. 30, 2009, entitled “Image Processing Method and Image Processing Apparatus”, and incorporates the Taiwan patent application in its entirety by reference.

TECHNICAL FIELD

The present disclosure relates to an image processing apparatus, and more particularly, to an image processing apparatus and a method thereof capable of solving edge blur of an object in an image.

BACKGROUND OF THE PRESENT DISCLOSURE

In a common image display system, e.g., a television (TV), a digital camera (DC) or a personal computer, considering a sawtooth edge created due to noise interferences or a scaled-down image (e.g., when a high-resolution image is converted into a low-resolution image), a low-pass filter is implemented to improve its image quality. Generally speaking, the low-pass filter generates a filtered luminance/chrominance value of a pixel by weighted-averaging the luminance/chrominance value of the pixel and luminance/chrominance values of neighboring pixels. After the low-pass filtering, an image edge of the low-pass filtered image data is relatively smooth.

However, although the low-pass filtering can reduce the image noises and solve the problem of a sawtooth edge, the image edge meanwhile becomes blurred due to the low-pass filtering. Referring toFIG. 1, suppose that an original image frame comprises two neighboring areas110and120of different colors (e.g., the color in the area110is yellow and the color in the area120is blue), and between the two neighboring areas110and120is an edge102. After a low-pass filtering, the edge102becomes blurred, and thus a blurred area104is formed in the vicinity of the edge102. Chrominance changes of the area102are illustrated with reference to chrominance values Cb and Cr at the bottom ofFIG. 1. Solid lines are distributions of chrominance values Cb and Cr of the original image frame, and dashed lines are distributions of chrominance values Cb and Cr of the area104after the low-pass filtering. As observed from the values Cb and Cr inFIG. 1, pixels in the area104have different colors.

In order to solve the problem of edge blur of the low-pass filtered image frame, a common approach is that the image display system performs edge enhancement on the low-pass filtered image frame. Following description is given with reference toFIG. 1andFIG. 2.FIG. 2shows a schematic diagram of a conventional method for solving the problem of edge blur of an image. CPi, CP1, and CPrinFIG. 2are respectively coordinate points of pixels Pi, P1, and Pr in color coordinate axes inFIG. 1. For the conventional method, the chrominance values Cb and Cr of the pixel Pi in the blurred area104are adjusted to the chrominance values Cb and Cr of the pixel P1or Pr to solve the problem of edge blur. For example, the image display system determines whether the value Cb of the pixel Pi is more approximate to the value Cb of the pixel P1or the pixel Pr, and defines the more approximate value Cb (i.e., the value Cb of the pixel P1or the pixel Pr) as an adjusted value Cb of the pixel Pi. Likewise, the image display system determines whether the value Cr of the pixel Pi is more approximate to the value Cr of the pixel P1or the pixel Pr, and defines the more approximate value Cr (i.e., the value Cb of the pixel P1or the pixel Pr) as an adjusted value Cr of the pixel P. An object of the foregoing method is to adjust the color of the area104to the color of the area110or the area120, so as to solve the problem of edge blur. However, with respect to a special situation inFIG. 2, the foregoing method may form another color at the image edge of the image frame to create image frame distortion. Referring toFIG. 2, since the value Cb of the pixel Pi is more approximate to the value Cb of the pixel P1, the adjusted value Cb of the pixel Pi is equal to the value Cb of the pixel P1; and since the value Cr of the pixel Pi is more approximate to the value Cr of the pixel Pr, the adjusted value Cr of the pixel Pi is equal to the value Cr of the pixel Pr. As illustrated inFIG. 2, the coordinate point CPi—adjof an adjusted chrominance value of the pixel Piin the color coordinate axes represents another color, which is different from a color (represented by a coordinate CP1) of the area110and a color (represented by a coordinate CPr) of the area120, and thus image quality of the image frame is deteriorated as the image frame distortion is created.

SUMMARY OF THE PRESENT DISCLOSURE

An object of the present disclosure is to provide an image processing method and an image processing apparatus to effectively solve the problem of edge blur without incurring image distortion.

According to an embodiment of the present disclosure, an image processing method comprises receiving an image data comprising a first pixel, a second pixel and a third pixel, all of which being neighboring pixels, the second pixel being between the first pixel and the third pixel; calculating a first difference between two initial chrominance values of the first pixel and two initial chrominance values of the second pixel and a second difference between the two initial chrominance values of the second pixel and two initial chrominance values of the third pixel; comparing the first difference with the second difference to select one of the first pixel and the third pixel as a target pixel, wherein the first pixel is selected as the target pixel when the first difference is smaller than the second difference, and the third pixel is selected as the target pixel when the first difference is larger than the second difference; and determining two adjusted chrominance values of the second pixel according to two initial chrominance values of the target pixel.

According to another embodiment of the present disclosure, an image processing apparatus comprises for receiving an image data and generating an adjusted image data, the image data at least comprising a neighboring pixels including a first pixel, a second pixel and a third pixel, the second pixel being between the first pixel and the third pixel. The image processing apparatus comprises a chrominance difference calculating unit, for calculating a first difference between two initial chrominance values of the first pixel and two initial chrominance values of the second pixel and a second difference between the two initial chrominance values of the second pixel and two initial chrominance values of the third pixel; a target pixel determining unit, for comparing the first difference with the second difference to select one of the first pixel and the third pixel as a target pixel, wherein the first pixel is selected as the target pixel when the first difference is smaller than the second difference, and the third pixel is selected as the target pixel when the first difference is larger than the second difference; and a chrominance adjusting unit, for determining the two adjusted chrominance values of the second pixel according to the two initial chrominance values of the target pixel.

According to yet another embodiment, an image processing method comprises receiving an image data comprising a first pixel, a second pixel and a third pixel, all of which being neighboring pixels, the second pixel being between the first pixel and the third pixel; calculating a first difference between an initial chrominance value of the first pixel and an initial chrominance value of the second pixel and a second difference between the initial chrominance value of the second pixel and an initial chrominance value of the third pixel, wherein the initial chrominance value is one of Cb value and Cr value; comparing the first difference with the second difference to select either the first pixel or the third pixel as a target pixel, wherein the first pixel is selected as the target pixel when the first difference is smaller than the second difference, and the third pixel is selected as the target pixel when the first difference is larger than the second difference; and determining an adjusted chrominance value of the second pixel according to the initial chrominance value of the target pixel and the initial chrominance value of the second pixel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 3shows a schematic diagram of an image processing apparatus300in accordance with an embodiment of the present disclosure. The image processing apparatus300comprises a low-pass filtering unit310and an image adjusting unit320. The mage adjusting unit320comprises a chrominance difference calculating unit321, a target pixel determining unit322, and a chrominance adjusting unit323. The image processing apparatus300may be applied to electronic products comprising screens for displaying image frames, e.g., TVs, personal computers, and DCs, and may be realized by software or hardware.

The following description is given with reference toFIG. 3andFIG. 4.FIG. 4shows a flow chart of performing by the image adjusting unit320of the image processing apparatus image processing on an initial image data Fin′ accordance with an embodiment of the present disclosure. The initial image data Fin′ is generated from an image data Finprocessed by the low-pass filtering unit310. Take a pixel P5in a frame500of the initial image data Fin′ as an example in the following description of the flow chart inFIG. 4.FIG. 5shows a schematic diagram of the frame500, each pixel of the frame500comprises two initial chrominance values (e.g., chrominance values Cb/Cr, UN or chrominance values compliant to other specifications, however, only the chrominance values Cb and Cr are taken as an example in the following description), and the two initial chrominance values Cb and Cr are low-pass filtered chrominance values.

In Step400, the chrominance difference calculating unit321calculates differences between two initial chrominance values Cb and Cr of the pixel P5and initial chrominance values Cb and Cr of neighboring pixels on two sides of the pixel P5. Suppose that there are a plurality of pixels (e.g., 2 to 15 pixels) between the two neighboring pixels and the pixel P5. For example, a pixel P1on the left side of the pixel P5and a pixel P9on the right side of the pixel P5are selected as the neighboring pixels. It is to be noted that, the pixel P1and the pixel P9described for illustration purposes shall not be construed as limiting the present disclosure. In other embodiment, the pixels P1and P9may also be replaced by other pixels on two sides of the pixel P5.

More specifically, the chrominance difference calculating unit321calculates a first difference d1between the initial chrominance values Cb and Cr of the pixel P5and initial chrominance values Cb and Cr of the pixel P1, and calculates a second difference d2between the initial chrominance values Cb and Cr of the pixel P5and initial chrominance values Cb and Cr of the pixel P9.FIG. 6shows a schematic diagram illustrating how the first difference d1and a second difference d2are determined. CP1, CP5and CP9are respectively values of coordinate points of the pixels P1, P5and P9in color coordinate axes, d1is calculated as d1=√{square root over ((CP1—Cb−CP5—Cb)2+(CP1—Cr−CP5—Cr)2)}{square root over ((CP1—Cb−CP5—Cb)2+(CP1—Cr−CP5—Cr)2)}, and d2is calculated as d2=√{square root over ((CP9—Cb−CP5—Cb)2+(CP9—Cr−CP5—Cr)2)}{square root over ((CP9—Cb−CP5—Cb)2+(CP9—Cr−CP5—Cr)2)}, where CP1—Cb, CP5—Cband CP9—Cbare respectively values of the coordinate points CP1, CP5and CP9on a coordinate axis Cb, and CP1—Cr, CP5—Cband CP9—Cbare respectively values of the coordinate points CP1, CP5and CP9on a coordinate axis Cr. It is to be noted that, the first difference d1inFIG. 6represents distances along the color coordinate axes between the initial chrominance values Cb and Cr of the pixel P5and the pixel P1, and the second difference d2represents a distance along the color coordinate axes between the initial chrominance values Cb and Cr of the pixel P5and the pixel P9. However, in other embodiments of the present disclosure, the first difference d1may be other values that represent the differences between the chrominance values Cb and Cr of the pixel P5and the pixel P1, and the second difference d2may be other values that represent the differences between the chrominance values Cb and Cr of the pixel P5and the pixel P9.

In Step402, the target pixel determining unit322compares the first difference d1with the second difference d2to select the pixel P1or the pixel P9as a target pixel. When the first difference d1is smaller than the second difference d2, it means that a color of the pixel P5is more approximate to that of the pixel P1, and the pixel P1is selected as the target pixel; otherwise, when the first difference d1is larger than the second difference d2, it means that the color of the pixel P5is more approximate to that of the pixel P9, and the pixel P9is selected as the target pixel. In Step404, the chrominance adjusting unit323directly adopts initial chrominance values Cb and Cr of the target pixel as adjusted chrominance values Cb and Cr of the pixel P5, and then performs on each pixel of the image data Fin′ image processing similar to that performed on the pixel P5, so as to output an adjusted image data Fout.

A significance of Step402and Step404is that, when the pixel P5(e.g., the pixel P5is regarded as the pixel P1inFIG. 1) is an image edge and the chrominance values Cb and Cr of the pixel P5are different from those of the pixel P1and the pixel P9due to the low-pass filtering, by using the foregoing method in Step402and Step404, the adjusted chrominance values Cb and Cr of the pixel P5become the same as those of the pixel P1or the pixel P9, thereby enhancing the image edge. In addition, in the embodiment inFIG. 3andFIG. 4, when the chrominance difference between the pixels P5and P1is smaller the chrominance difference between the pixels P9and P1, the chrominance adjusting unit323regards the chrominance values Cb and Cr of the pixel P1as the adjusted chrominance values Cb and Cr of the pixel P5; when the chrominance difference between the pixels P5and P1is bigger the chrominance difference between the pixels P9and P1, the chrominance adjusting unit323regards the chrominance values Cb and Cr of the pixel P9as the adjusted chrominance values Cb and Cr of the pixel P5. Accordingly, variances in the adjusted chrominance values of the pixel P5may be slight, and the image edge is then free from any significant distortions.

Although the embodiment inFIG. 3andFIG. 4are capable of enhancing the image edge without incurring image distortion, the image processing method inFIG. 4may still create image distortion with respect to two following particular situations. Under a first situation, the color of the pixel P5is different from that of the pixel P1or the pixel P9, i.e., the pixel P5is not only at an edge between two colors of the pixel P1and P9. For example, supposing that in the image data Fin, initial colors of the pixels P1to P4are yellow, the initial color of the pixel P5is orange, initial colors of the pixel P6to P9are blue (e.g., the pixels P1to P9of the initial image data Fin′ have similar colors to those of the image data Fin), in the first situation, the adjusted pixel P5changes to yellow or blue (i.e., the initial orange color disappears), thus causing image distortion. In addition, under a second situation, the pixels P1to P9are gradient color pixels, i.e., colors of the pixels P1to P9with a same color tone have gradually increased or gradually reduced saturations (e.g., colors changing from pale red to dark red). Under the second situation, the adjusted colors of the pixels P1to P9cannot truly represent gradient color pixels when the method inFIG. 3andFIG. 4are applied. For example, a relatively large difference may be formed between color saturations represented by adjusted chrominance values of the pixels P3and P4, such that an obvious edge is formed, and accordingly thus causing image distortion.

FIG. 7shows a schematic diagram of an image processing apparatus700in accordance with another embodiment of the present disclosure for solving the foregoing problem. The image processing apparatus700comprises a low-pass filtering processing unit710and an image adjusting unit720. The image adjusting unit720comprises a chrominance difference calculating unit721, a target pixel determining unit722, a chrominance high-frequency (HF) parameter determining unit723, a chrominance low-frequency (LF) parameter determining unit724, and a chrominance adjusting unit725.

The following description is given with reference toFIG. 7andFIG. 8.FIG. 8shows a flow chart of performing image processing by an image adjusting unit720of an image processing apparatus700on an initial image data Fin′ in accordance with another embodiment of the present disclosure. The initial image frame data Fin′ is generated from an image data Finprocessed by the low-pass filtering unit710. The pixel P5in the frame500(inFIG. 5) of the image frame data Fin′ is taken as an example in the following description of the flow chart inFIG. 8. Each pixel of the frame500comprises two initial chrominance values that are low-pass filtered.

In Step800, the chrominance difference calculating unit721calculates differences between initial chrominance values Cb and Cr of the pixel P5and those of two neighboring pixels on two sides of the pixel P5, and there are a plurality of pixels (e.g., 2 to 15 pixels) between the two neighboring pixels, e.g., a pixel P1on the left side of the pixel P1, and a pixel P9on the right side of the pixel P5. In the following description, the pixel P1and the pixel P9described for illustration purposes shall not be construed as limiting the present disclosure, and in other embodiments, the pixels P1and P9may also be replaced by other pixels on two sides of the pixel P5.

More specifically, the chrominance difference calculating unit721calculates differences between the initial chrominance values Cb and Cr of the pixel P5and those of the pixel P1to determine a first difference d1, and calculates differences between the initial chrominance values Cb and Cr of the pixel P5and those of the pixel P9to determine a second difference d2.FIG. 6shows a schematic diagram illustrating how the first difference d1and the second difference d2are determined, where CP1, CP5and CP9are respectively values of coordinate points of the pixel P1, P5and P9in color coordinate axes. It is to be noted that, the first difference d1inFIG. 6is a distance along the color coordinate axes between the chrominance values Cb and Cr of the pixel P5and the pixel P1, and the second difference d2is a distance along the color coordinate axes between the chrominance values Cb and Cr of the pixel P5and the pixel P9. However, the differences d1and d2are not limitations of the present disclosure. In other embodiments of the present disclosure, the first difference d1is other values that represent the differences between the chrominance values Cb and Cr of the pixel P5and those of the pixel P1, and the second difference d2is other values that represent the difference between the chrominance values Cb and Cr of the pixel P5and those of the pixel P9.

In Step802, the target pixel determining unit722compares the first difference d1and the second difference d2to select either the pixel P1or the pixel P9as a target pixel. When the first difference d1is smaller than the second difference d2, it means that an initial color of the pixel P5is more approximate to that of the pixel P1, and the pixel P1is selected as the target pixel; otherwise, when the first difference d1is greater than the second difference d2, it means that the initial color of the pixel P5is more approximate to that of the pixel P9, and the pixel P9is selected as the target pixel.

A significance of the chrominance HF parameter VHFis described with reference toFIG. 9(a) showing a schematic diagram of initial chrominance values Cb/Cr of the pixels P1to P9when there is no third color pixel between the pixel P1and the pixel P9(i.e., the chrominance change degree of the pixel P1to the pixel P9is small). Since the initial chrominance values Cb/Cr of the pixels P1to P9are represented by a smooth curve inFIG. 9(a), Cb_end_diff and Cr_end_diff respectively approximate to Cb_sum_diff and Cr_sum_diff, such that the calculated chrominance HF parameter VHFis relatively small.FIG. 9(b) shows a schematic diagram of the initial chrominance value Cb/Cr of the pixels P1to P9when there is a third color tone between the pixel P1and the pixel P9(i.e., the chrominance change degree of the pixel P1to the pixel P9is large). Since the initial chrominance value Cb/Cr of the pixels P1to P9is drastically changed, Cb_end_diff is larger than Cb_sum_diff and Cr_sum_diff is larger than Cr_end_diff, and accordingly the chrominance change degree in the pixel P1to the pixel P9of the image data Finis determined according to the calculated chrominance HF parameter VHF.

It is to be noted that, the foregoing formula for calculating the chrominance HF parameter VHFis applied in this embodiment for example, and in other embodiments of the present disclosure, the chrominance HF parameter VHFcan be calculated by other formulae provided that the chrominance HF parameter VHFcan reflect the chrominance change in the pixel P1to the pixel P9(i.e., the change in the pixel P1to the pixel P9of the image data Finoriginally having a third type of color different from colors of the pixel P1and the pixel P9). Various other methods may also be adopted to calculate the chrominance HF parameter VHF—such modifications are within the spirit and scope of the present disclosure.

Generally speaking, when the pixels P1to P9are gradient color pixels, the initial chrominance values Cb and Cr of the pixel P1are extremely approximate to those of the pixel P9(for that the gradient color pixels are the same color with different saturations). Accordingly, the foregoing Cb_diff and Cr_diff are extremely small, such that the chrominance LF parameter VLFis relatively large. On the contrary, when the pixels P1to P9are not gradient color pixels, the chrominance values Cb and Cr of the pixels P1and P9are relatively large, such that the chrominance LF parameter VLFis relatively small. In addition, the foregoing formulae for calculating Cb_diff and Cr_diff may be modified, e.g., differences between initial chrominance values Cb and Cr of the pixel P5and those of the neighboring pixels are calculated to determine the chrominance LF parameter VLFas:
Cb_diff=|CbP5−CbP3|+|CbP5−CbP7|  (7.2)
Cr_diff=|CrP5−CrP3|+|CrP5−CrP7|  (8.2)

It is to be noted that, the foregoing formulae for calculating the chrominance LF parameter VLFis applied in this embodiment as an example, and in other embodiments of the present disclosure, the chrominance LF parameter VLFmay be calculated by other formulae provided that the chrominance LF parameter VLFcan truly reflect the degree of the gradient color in the range between the pixel P1and the pixel P9. Various other methods may also be applied to calculate the chrominance LF parameter VLF—such modifications are within the spirit and scope of the present disclosure.

In Step808, the chrominance adjusting unit725determines a weight W according to the first difference d1, the second difference d2, the chrominance HF parameter VHFand the chrominance LF parameter VLF. In Step810, the chrominance adjusting unit725respectively weighted-averaging two initial chrominance values of the pixel P5and two initial chrominance values of the target pixel to obtain two adjusted chrominance values of the pixel P5, and the two adjusted chrominance values are calculated as:
CbP5—adj=W*CbPtar+(1−W)*CbP5(9)
CFP5—adj=W*CrPtar+(1−W)*CFP5(10)
Wherein, CbP5—adjand CrP5—adjare adjusted chrominance values Cb and Cr of the pixel P5, CbPtarand CrPtarare respectively initial chrominance values Cb and Cr of the target pixel (i.e., one of the pixel P1and the pixel P9), and CbP5and CrP5—adjare respectively of initial chrominance values Cb and Cr of the pixel P5.

The weight W is calculated as:
W=W1*W2*W3(11)
Wherein, W1is obtained according to a difference between the first difference d1and the second difference d2via a calculation or a lookup table with reference to a first weight curve shown inFIG. 10; W2is obtained according to the chrominance HF parameter VHFvia a calculation or a lookup table with reference to a second weight curve shown inFIG. 11; and W3is obtained according to the chrominance VLFvia a calculation or a lookup table with reference to a third weight curve shown inFIG. 12.

It is appreciated fromFIG. 10toFIG. 12and the description of determining the weight W that, under situations that other parameters stay unchanged (e.g., the chrominance HF parameter VHFand the chrominance LF parameter VLFstay unchanged), the weight W is positively correlated with the difference (e.g., |d1−d2|) between the first difference d1and the second difference d2. Further, a significance of the positive correlation lies in that, when the difference between the first difference d1and the second difference d2is large, it means that the initial chrominance values Cb and Cr of the pixel P5are extremely approximate to the initial chrominance values Cb and Cr of the target pixel (i.e., the pixel P1or the pixel P9). Therefore, even if the weight W of the initial chrominance values Cb and Cr of the target pixel is large, chrominance distortion of the pixel P5shall not be resulted. Otherwise, when the difference between the first difference d1and the difference d2is small, it means that the initial chrominance values Cb and Cr of the pixel P5are intermediate values of the initial chrominance values Cb and Cr of the pixel P1or the pixel P9, i.e., when the initial chrominance values Cb and Cr of the pixel P5are adjusted according to the initial chrominance values Cb and Cr of the pixel P1or the pixel P9, a relatively large error is likely to be incurred, such that chrominance distortion of the pixel P5is created. Therefore, the weight W of the initial chrominance values of the target pixel is designed as being relatively low, i.e., the initial chrominance values Cb and Cr of the pixel P5are adjusted as least as possible, and the adjusted chrominance values Cb and Cr of the pixel P5are approximate to its initial chrominance values Cb and Cr.

When the difference between the first difference d1and the second difference d2(e.g., |d1−d2|) stays unchanged, the weight W is approximately negatively correlated with the chrominance HF parameter VHFand the chrominance LF parameter VLF, i.e., when chrominance values of the pixels P1to P9drastically change (i.e., the chrominance HF parameter VHFis high) or the pixels P1to P9exhibit a gradient color (i.e., the chrominance LF parameter VLFis high), the weight W is designed as being relatively low, so as to adjust the chrominance values Cb and Cr of the pixel P5as least as possible. Therefore, the adjusted chrominance values Cb and Cr of the pixel P5are approximate to its initial chrominance values Cb and Cr.

It is to be noted that, the diagrams of the weights W1, W2and W3inFIG. 10toFIG. 12are implemented in this embodiment as an example. In other embodiments of the present disclosure, provided that the weight W1is approximately positively correlated with the difference between the first difference d1and the second difference d2, the weight W2is approximately negatively correlated with the chrominance HF parameter VHF, and W3is approximately negatively correlated with the chrominance LF parameter VLF, the weights W1, W2and W3may also be calculated by other formulae. In addition, in another embodiment of the present disclosure, the weight W is directly generated according to the first difference d1, the second difference d2, the chrominance HF parameter VHFand the chrominance LF parameter VLFvia a calculation formula or a lookup table.

After the chrominance adjusting unit725performs image processing similar to that performed on the pixel P5on each pixel of the image frame data Fin′, an adjusted image frame data Foutis outputted.

In addition, it is to be noted that, the first difference d1, the second difference d2, the chrominance HF parameter VHFand the chrominance LF parameter VLFare simultaneously taken into consideration, and the foregoing weight W is determined according to all of the weights W1, W2and W3. However, in other embodiments of the present disclosure, only certain parameters from the first difference d1, the second difference d2, the chrominance HF parameter VHFand the chrominance LF parameter VLFis taken into consideration, and the weight W is determined according to one or two of the weights W1, W2and W3. For example, when only influences brought by the chrominance HF parameter VHFneeds to be considered (i.e., the chrominance LF parameter determining unit724may be removed, and some functions of the chrominance adjusting unit725may be also be removed), the chrominance adjusting unit725weighted-averages the initial chrominance values Cb and Cr of the pixel P5and the initial chrominance values Cb and Cr of the target pixel to obtain two adjusted chrominance values of the pixel P5, and the two adjusted chrominance values are calculated as:
CbP5—adj=W2*CbPtar+(1−W2)*CbP5(12)
CrP5—adj=W2*CrPtar+(1−W2)*CrP5(13)

In another example, when only influences brought by the chrominance LF parameter VLFneeds to be considered (i.e., the chrominance LF parameter determining unit723may be removed, and some functions of the chrominance adjusting unit725may be also be removed), the chrominance adjusting unit725weighted-averages the initial chrominance values Cb and Cr of the pixel P5and the initial chrominance values Cb and Cr of the target pixel to obtain two adjusted chrominance values of the pixel P5, and the two adjusted chrominance values are calculated as:
CbP5—adj=W3*CbPtar+(1−W3)*CbP5(14)
CrP5—adj=W3*CrPtar+(1−W3)*CrP5(15)
Other combination approaches (e.g., only the first difference d1and the second difference d2are taken into consideration, or the first difference d1, the second difference d2and the chrominance LF parameter VLFare taken into consideration) are readily apparent to a person having ordinary skills in the art after reading the foregoing description, and details thereof shall not be described for brevity.

In addition, in the embodiment inFIG. 7andFIG. 8, the chrominance difference calculating unit721calculates differences between two initial chrominance values of the pixel P5and those of the pixel P1to determine the first difference d1, calculates the differences between the two initial chrominance values of the pixel P5and those of the pixel P9to determine the second difference d2, and weighted-averages the two initial chrominance values of the pixel P5and the two initial chrominance values of the target pixel to obtain two adjusted chrominance values of the pixel P5. However, in another embodiment of the present disclosure, the chrominance difference calculating unit721may only calculate a difference between one initial chrominance value (e.g., the initial chrominance value Cb) of the pixel P5and that of the pixel P1to determine a first difference d1, and calculate a difference between the initial chrominance value Cb of the pixel P5and that of the pixel P9to determine a second difference d2. After that, the target pixel determining unit722compares the first difference d1with the second difference d2to select either the pixel P1or the pixel P9as a target pixel. The chrominance HF parameter determining module723determines a chrominance HF parameter VHFof the pixels P1to P9for representing a change in initial chrominance values of the pixels P1to P9is calculated via Formula (1) or calculated as:
VHF=|Cb_end_diff−Cb_sum_diff|  (16)

Wherein, Cb_end_diff and Cb_sum_diff are calculated with reference to Formula (2) and Formula (3). In addition, the chrominance LV parameter VLFdetermines a chrominance LF parameter VLFof the pixels P1to P9for presenting a degree of the gradient color of initial chrominance values of the pixels P1to P9is calculated via Formula (6) or calculated as:
VLF=|1/Cb_diff|  (17)
Wherein, Cb_diff is calculated with reference to Formula (7.1).

The chrominance adjusting unit725weighted-averages the initial chrominance value Cb of the pixel P5and the initial chrominance value Cb of the target pixel to obtain and adjusted chrominance value Cb calculated as:
CbP5—adj=W*CbPtar+(1−W)*CbP5(18)
Wherein, W is determined according to one or several of the first difference d1, the second difference d2, the chrominance HF parameter VHFand the chrominance LF parameter VLF, and details thereof being with reference to the description of Step808are readily apparent to a person having ordinary skills in the art after reading the foregoing description, and shall not be described for brevity.

In conclusion, according to an image processing apparatus and an image processing method of the present disclosure, a degree for adjusting image chrominance is determined according to one or several parameters from a difference between a first difference and a second difference, a chrominance HF parameter and a chrominance LF parameter. Accordingly, a problem of image edge blur is effectively solved without incurring image distortion.