Patent Application
20090123068
1. Field of the Invention
The present invention relates to image processing. More particularly, the present invention relates to a method and apparatus for adaptively adjusting an image.
2. Description of Related Art
Image processing modifies various image attributes, such as color, brightness, or to combine photographs. For example, some functions of the image processing, e.g., the modification of the brightness and the contrast, are used to quickly change a photograph of a sunny day to a photograph of a rainy day. The modification of the image can further be processed by selection, cut and paste.
In order to improve the display quality of the flat panel display, the image can be dynamically adjusted, for example, according to the brightness of the image. For a dark image, the adjustments are made to increase the contrast, reduce the brightness, and reduce the light source. For a bright image, the adjustments are made to reduce the contrast, increase the brightness, and increase the light source.
The image mean brightness is a usually used judgment index for some image processing.
However, in many cases, it is not sufficient to adjust the images merely by the mean brightness values. For example, for two images as shown in
Accordingly, the present invention is directed to providing a method for adaptively adjusting an image and an image processing apparatus using the same, which are capable of generating and analyzing a gray-level distribution of image pixels, so as to adjust the image to the optimal quality according to the gray-level distribution.
The present invention provides a method for adaptively adjusting the image. The method at least includes providing an image having a plurality of pixels, generating a gray-level distribution of the pixels, and searching a specific gray-level according to the gray-level distribution. A specific percentage of the pixels have gray-levels smaller than the specific gray-level. Next, the image is further adjusted according to the specific gray-level.
In the method according to the preferred embodiment of the present invention, wherein the step of generating the gray-level distribution of the pixels includes counting the number of the pixels of each gray-level. In another embodiment of the present invention, the specific percentage is approximately 90%. In still another embodiment of the present invention, the step of adjusting the image includes applying the brightness gain to the image and adjusting the contrast of the image according to the specific gray-level.
In the method according to the preferred embodiment of the present invention, the image is displayed on a screen having a light source, and the step of adjusting the image includes adjusting the brightness of the light source and adjusting the contrast of the image according to the specific gray-level. In another embodiment of the present invention, the step of adjusting the brightness of the light source includes determining the brightness of the light source through looking up a table by using the specific gray-level as an index. In still another embodiment of the present invention, the step of adjusting the contrast of the image includes determining the contrast of the image through looking up a table by using the specific gray-level as an index.
The present invention further provides an image processing apparatus. The apparatus includes a statistics apparatus and an image adjustment apparatus. The statistics apparatus is used to receive a plurality of pixels of an image, and generate a gray-level distribution of the pixels, and search a specific gray-level according to the gray-level distribution. The image adjustment apparatus is used to adjust the image according to the specific gray-level, wherein a specific percentage of the pixels have gray-levels smaller than the specific gray-level.
In the apparatus according to the preferred embodiment of the present invention, the image adjustment apparatus includes a brightness adjustment apparatus and a contrast adjustment apparatus. The brightness adjustment apparatus and the contrast adjustment apparatus respectively give a brightness gain and a contrast adjustment parameter to the image according to the specific gray-level. In another embodiment of the present invention, the image is displayed on a screen having a light source, and the image adjustment apparatus includes a brightness adjustment apparatus. The brightness adjustment apparatus adjusts the brightness of the light source according to the specific gray-level. In still another embodiment of the present invention, the brightness adjustment apparatus includes a gray-level/brightness table, and the brightness of the light source is determined through looking up the table by using the specific gray-level as an index.
In the apparatus according to the preferred embodiment of the present invention, the contrast adjustment apparatus includes a gray-level/contrast table, and the contrast of the image is determined through looking up the table by using the specific gray-level as an index. In another embodiment of the present invention, the statistics apparatus is further used for counting the number of the pixels of each gray-level. In still another embodiment of the present invention, the specific percentage is substantially approximately 90%.
In the present invention, the statistics apparatus generates the gray-level distribution of the image pixels, and searches a specific gray-level according to the gray-level distribution of the image pixels, so as to further adjust at least the brightness and the contrast parameter of the image according to the obtained specific gray-level, thereby making the image have the optical quality.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Next, the image is transmitted to the statistics apparatus 401 to generate a histogram that includes the statistics of the gray-level distribution of the image pixels (step S302). In the step S302, the statistics apparatus 401 performs a pixel-gray-level analysis on the whole image, for 256 gray-levels, to found out how many pixels each gray-level has. For example, the number of the image pixels with a gray-level value of 0 is 100. The number of the image pixels with a gray-level value of 1 is 20, the number of the image pixels with a gray-level value of 2 is 10, and so on. In the statistics generating process, the number of the pixels in each gray-level is record, and it is shown as a distribution curve H1, referred to a gray-level histogram, as shown
Next, a specific gray-level is found out according to the accumulation curve S1 of the gray-level distribution, and the gray-levels of a specific percentage of pixels among the image are smaller than the specific gray-level (step S303). In order to make this embodiment be clearer, here it is assumed that the specific percentage is 90%. Therefore, the specific gray-level actually represents that 90% pixels among the image have gray-levels smaller than the specific gray-level. The specific gray-level obtained from the image in
Finally, the image is adjusted according to the specific gray-level (step S304). The statistics apparatus 401 respectively transmits the specific gray-level to the brightness adjustment apparatus 403 and to the contrast adjustment apparatus 404. The brightness adjustment apparatus 403 may apply a brightness gain to the image according to the specific gray-level, and may further adjust the brightness of the light source accordingly (step S305). The contrast adjustment apparatus 404 applies a contrast adjustment parameter according to the specific gray-level to adjust the contrast of the image (step S306). In addition to the contrast and the brightness, the image adjustment apparatus 402 can adjust other image attributes, and it is not described here.
The brightness adjustment apparatus 403 determines the magnitude of the brightness gain by looking up a gray-level/brightness table according to the specific gray-level as a judgment index for applying the brightness gain to the image and adjusting the brightness of the light source, such that the displayed image is optimized. For example, in
The contrast adjustment apparatus 404 determines the magnitude of the contrast adjustment parameter by looking up a gray-level/contrast table according to the specific gray-level as a judgment index. For example, as shown in
As described in the conventional art, the method of using the mean brightness value as the judgment index can not properly adjust the image, thus easily resulting in the unsuitable processed image. In the embodiment of the present invention, the method of obtaining the judgment index according to the gray-level histogram results in suitable processed image.
Taking the images with the same mean brightness value (as shown in
Further, the contrast adjustment value/brightness adjustment value of the images shown in
It is noted that although in the above embodiment, a possible type of the image processing apparatus is described, but those of ordinary skill in the art should know that the design manners of various manufacturers on the statistics apparatus 401 and the image adjustment apparatus 402 are diverse, so the application of the present invention is not limited to the possible type. In another word, as long as the statistics apparatus 401 can make analysis and statistics of the gray-level distribution of the images, and can find out a specific gray-level according to the gray-level distribution, so as to adjust the image and improve the image quality, the spirit of the present invention is satisfied.
In view of the above, in the present invention, the statistics apparatus is adopted to make statistics and analysis of the gray-level distribution, and to adjust the brightness and the contrast of the image according to the gray-level distribution of the pixels, such that the image has an optimal display quality. Therefore, the present invention can effectively analyze the bright and dark components of various images, and can adjust the images to the optimal quality according to the gray-level distribution of each image.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
