1. Field of the Invention
The invention relates to a color processing system and, more particularly, to a color noise suppressing system for processing abnormal part of an image to suppress color noise.
2. Description of Related Art
Currently, with rapidly developed multimedia technologies, multimedia devices (such as DVD player, digital camera, digital video camera) are in wide spread use. The performance of multimedia devices is essentially based on image quality. However, when taking a scenic photo, because of limited capabilities of devices, color noises may appear on an image. For example, a typical CCD image sensor can easily produce noises at a low light or a slow shutter. In addition, during an image preparation or process (such as an MPEG compression), color spots may appear due to partial image data loss or change.
To overcome this, U.S. Pat. No. 4,680,624 discloses two types of color noise suppression. One is based on chroma degree of a color signal. When the chroma degree is smaller than a threshold level, the color signal is suppressed to reduce color noises. However, such a way also reduces some image saturation or even damages a normal image. The other is based on luma degree. When the luma degree is smaller than a threshold level, the color signal is suppressed to reduce color noises. However, such a way cannot easily reduce color noises in a bight gray scale image. In addition, when suppressing dark color noises such as green spots, a normal blue or red image at a same luma as a green image may be damaged since a green color typically has a higher luma. Therefore, it is desirable to provide an improved color noise suppression to mitigate and/or obviate the aforementioned problems.
An object of the invention is to provide a color noise suppressing system, which can eliminate color noises in a bright gray scale image without reducing image saturation.
Another object of the invention is to provide a color noise suppressing system, which can eliminate dark color noises without reducing tints of other dark normal images.
According to a feature of the invention, a color noise suppressing system is provided. The system includes a converter, a saturation compute device and a color suppressor. The converter converts a YUV image signal into an RGB image signal. The saturation compute device is connected to the converter for computing a saturation from the RGB image signal and converting the saturation into a gain. The chroma suppressor is connected to the saturation compute device for performing chroma suppression on the YUV image signal according to the gain.
According to another feature of the invention, a color noise suppressing system is provided. The system includes a converter, a maximum compute device and a color suppressor. The converter converts a YUV image signal into an RGB image signal. The maximum compute device is connected to the converter for computing a maximum from the RGB image signal and converting the maximum into a gain. The chroma suppressor is connected to the maximum compute device for performing chroma suppression on the YUV image signal according to the gain.
According to a further feature of the invention, a color noise suppressing system is provided. The system includes a converter, a saturation compute device, a maximum compute device and a chroma suppressor. The converter converts a YUV image signal into an RGB image signal. The saturation compute device is connected to the converter for computing a saturation from the RGB image signal and converting the saturation into a first gain. The maximum compute device is connected to the converter for computing a maximum from the RGB image signal and converting the maximum into a second gain. The chroma suppressor is connected to the saturation compute device and the maximum compute device for performing chroma suppression on the YUV image signal according to the first and second gains.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
The color noise suppressing system 500 connected to the converter 400 includes a YUV to RGB converter 510, a saturation compute device 520, a maximum compute device 530 and a chroma suppressor 540. The converter 510 converts the YUV image signal into the RGB image signal. The saturation compute device 520 is connected to the converter 510 for computing a saturation from the RGB image signal and converting the saturation into a first gain. The maximum compute device 530 is connected to the converter 510 for computing a maximum from the RGB image signal and converting the maximum into a second gain. The chroma suppressor 540 is connected to the saturation compute device 520 and the maximum compute device 530 for performing chroma suppression on the YUV image signal according to the first and second gains.
The saturation compute device 520 computes a saturation S of RGB image signal of each pixel based on the following equation (1):
where R, G, B are respective red, green, blue values of the pixel, and S ranges from zero to one. Further, a corrected saturation SS is given by the following equation (2):
SS=fix(S×255), (2)
where the function fix( ) takes a closest and smallest integer of the parameter.
Next, the corrected saturation SS is converted into the first gain UVcoeff1 according to a corrected saturation to first gain conversion curve shown in
The maximum compute device 530 computes a respective maximum Max(R, G, B) according to RGB image signal of each pixel. Next, the maximum Max(R, G, B) is converted into a second gain UVcoeff2 according to a RGB maximum to second gain conversion curve shown in
The chroma suppressor 540 performs a multiplication on U image signal and V image signal of each pixel according to the first gain UVcoeff1 and the second gain Uvcoeff2 of the pixel, respectively. Namely, the device 540 outputs U image signal of the pixel as U*UVcoeff1*UVcoeff2 and V image signal of the pixel as V*UVcoeff1*UVcoeff2, where Uvcoeffl is the first gain, UVcoeff2 is the second gain, and U and V are the U image signal and the V image signal output by the device 400.
As cited, the inventive saturation compute device 520 adjusts respective UV value according to RGB signal of each pixel, which can eliminate color noises in a bright gray scale image without reducing any image saturation, as cited in the prior art. In addition, the inventive maximum compute device 530 adjusts respective UV value according to a maximum RGB signal of each pixel, which can easily eliminate color noises in a dark gray scale image without reducing luma of other colors, i.e., blue and red, as cited in the prior art.
Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.
Number | Date | Country | Kind |
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093133011 | Oct 2004 | TW | national |