TWI556642B - Day and night mode switching method for image capture device - Google Patents

Description

Day and night mode switching method of image capturing device

The invention relates to a method for switching an operation mode of an image capturing device, in particular to a method for switching between a day mode and a night mode.

With the rapid development of multimedia and network technologies, image capture devices have been widely used in life. For example, in response to the increasing demand for security surveillance in recent years, network cameras have been widely used in road surveillance, elderly care, access control and security.

In the existing network camera, the photosensitive module is generally configured to detect the brightness of the current environment, and compare the brightness of the environment with the preset value of the system, and then according to the comparison result, whether to switch from the daytime color image mode to Grayscale image mode at night. However, existing network cameras need to be equipped with a photosensitive module that detects the brightness of the current environment, so a high hardware cost is required.

Accordingly, it is an object of the present invention to provide a day and night mode switching method for an image capture device.

Therefore, the day and night mode switching method of the image capturing device of the present invention is performed by an image capturing device, and a current running mode of the image capturing device The formula is one of a day mode and a night mode. The day/night mode switching method of the image capturing device comprises the following four steps:

In step (a), the image capturing device captures a plurality of consecutive images related to the current operating mode, wherein each image includes a plurality of pixels, and each pixel has a brightness value.

In step (b), the image capturing device calculates a global luminance average value of each image, wherein the global luminance average value is an average value of luminance values of all pixels of the image.

In step (c), for each image, the image capturing device determines a plurality of different function values included in the range according to a value range of a cumulative distribution function of luminance values of all pixels of the image. The interval is calculated, and an interval luminance average value of each function value interval is calculated, wherein the interval luminance average value is an average value of all luminance values corresponding to the function value interval.

In step (d), the image capturing device switches the current operating mode between the day mode and the night mode according to the global brightness average of the images and the interval brightness averages.

The effect of the present invention is that the image capturing device can switch the current operating mode between the day mode and the night mode by calculating the global brightness average of the continuous image and the average brightness of the intervals. .

10~19‧‧‧Steps

Other features and effects of the present invention will be apparent from the following description of the drawings. FIG. 1 is a flow chart illustrating the day and night mode of the image capturing device of the present invention. Step flow of the switching method; and FIG. 2 is a schematic diagram illustrating a cumulative distribution function of image pixel luminance values and a plurality of function value intervals associated with the cumulative distribution function.

Referring to FIG. 1, the day/night mode switching method of the image capturing device of the present invention is performed by an image capturing device such as a webcam. A current operating mode of the image capturing device is one of a day mode and a night mode. The step flow of the method is detailed below.

First, in step 10, the image capturing device captures an image, wherein the image includes a plurality of pixels, and each pixel has a Luminance Value.

Next, in step 11, the image capturing device calculates a global brightness average of the image, wherein the global brightness average is an average of the brightness values of all pixels of the image.

Next, in step 12, the image capturing device determines whether the current operating mode is the day mode, and when the determination result is positive, proceeds to step 13; otherwise, the image capturing device determines that the current operating mode is the night mode, and Go to step 15.

In step 13, the image capturing device determines whether there is a continuous W _C image that satisfies the global brightness average of the image is less than a predetermined brightness average threshold, where W _C is an integer and not less than 1. When the judgment result is affirmative, the image capturing device performs step 14, that is, switches the current operation mode from the day mode to the night mode; otherwise, returns to step 10 to capture the next image.

In step 15, referring to FIG. 2, the image capturing device determines, according to a value range of a Cumulative Distribution Function of the luminance values of all the pixels of the image, a different one included in the value range. A function value interval, a second function value interval, a third function value interval, and a fourth function value interval, and calculate an interval luminance average value of each function value interval. Wherein, the value range is [0, 1]; the average value of the interval brightness is an average value of all the brightness values corresponding to the function value interval; the upper and lower bounds of the first function value interval are 1-T ₁ and 0 respectively The upper and lower bounds of the second function value interval are respectively T ₂ and 0, and the upper and lower bounds of the third function value interval are 1 and T ₁ , respectively, and the upper and lower bounds of the fourth function value interval are respectively 1 and 1-T ₂ , wherein, preferably, T _{1 is} in the range of 0.05 to 0.35, and T _{2 is} in the range of 0.4 to 0.6.

For example, as shown in FIG. 2, the fourth function value interval is [0.5, 1], and the luminance values corresponding to the cumulative distribution function values of 0.5 and 1 are respectively M and N, where M < N, Therefore, the interval luminance average value of the fourth function value interval is an average value of all luminance values in the range of M to N among the luminance values of the pixels; for example, if the image has a luminance value of 100 pixels In the range of M to N, the average value of the interval luminance of the fourth function value interval is the average value of the luminance values of the 100 pixels.

Next, in step 16, the interval luminance average value of the first function value interval is Y _D1 , and the interval luminance average value of the second function value interval is Y _D2 , and the interval luminance average value of the third function value interval is Y _B1 , and the average brightness of the interval of the fourth function value interval is Y _B2 , the image capturing device calculates a first brightness difference S ₁ , a second brightness difference S ₂ , and a third brightness of the image. The difference S ₃ , where S ₁ =|Y _D1 -Y _B1 |, S ₂ =|Y _D2 -Y _B2 |, and S ₃ =|S ₁ -S ₂ |.

Next, in step 17, the image capturing device calculates an individual threshold value of the pair of image images based on the third brightness difference value. Preferably, the preferred embodiment is: preparing a plurality of reference images having different third brightness difference values in different scenes with an ambient illuminance of 8 to 10 lux (Lux), and wherein the third brightness is The difference value includes all possible values of the third luminance difference value; for example, if the luminance value of one pixel is represented by eight bits, all possible values of the third luminance difference value are 0 to 255. The individual threshold value is set to the global luminance average of the reference image having the same third luminance difference value as the image.

Then, in step 18, the image capturing device determines whether there are consecutive W _C images in the images that satisfy the "the average brightness of the image is not less than the individual threshold value corresponding to the image" and "the third of the image." The brightness difference is less than a predetermined brightness difference threshold value. When the judgment result is affirmative, the image capturing device performs step 19, that is, switches the current operation mode from the night mode to the day mode; otherwise, returns to step 10 to capture the next image.

In summary, the day and night mode switching method of the image capturing device of the present invention calculates the global brightness average value of the continuous image and calculates the third brightness according to the cumulative distribution function of the pixel brightness value of each image. The difference, the image capturing device can determine whether the current operating mode should be switched from the day mode to the night mode, or the night mode to the day mode; and the method does not need to be configured to detect the current ambient brightness mold Therefore, the cost of the hardware can be effectively reduced, so that the object of the present invention can be achieved.

However, the above is only the embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and the patent specification of the present invention are still It is within the scope of the patent of the present invention.

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Claims (5)

A day and night mode switching method of an image capturing device is performed by an image capturing device, wherein a current operating mode of the image capturing device is one of a day mode and a night mode, and the image capturing device is day and night The mode switching method includes the following steps: (a) the image capturing device captures a plurality of consecutive images related to the current operating mode, wherein each image includes a plurality of pixels, and each pixel has a brightness value. (b) the image capture device calculates a global luminance average of each image, wherein the global luminance average is an average of luminance values of all pixels of the image; (c) for each image, The image capturing device determines a plurality of different function value intervals included in the range according to a value range of a cumulative distribution function of luminance values of all pixels of the image, and calculates one of each function value interval. An interval average value, wherein the interval brightness average is an average value of all brightness values corresponding to the function value interval; and (d) the image capturing device is based on the global brightness average of the images and The average value of the luminance range other current operating mode switching between the day mode and the night mode. The method for switching between day and night modes of the image capturing device according to claim 1, wherein in step (c), the image capturing device determines a first function value interval, a second function value interval, and a third function. a value interval, and a fourth function value interval, and the step (d) includes the following sub-steps: (d-1) for each image, the image capturing device calculates a first brightness difference value, a second image of the image a brightness difference value, and a third brightness difference value, and calculating an individual threshold value of the pair of image images according to the third brightness difference value, wherein the first brightness difference value is an interval brightness average of the first function value interval An absolute value of a difference between a value and an interval luminance average value of the third function value interval, wherein the second luminance difference value is an interval luminance average value of the second function value interval and an interval luminance average value of the fourth function value interval An absolute value of the difference, and the third brightness difference is an absolute value of a difference between the first brightness difference and the second brightness difference; and (d-2) when the image capturing device determines the current value operating mode for night mode, and such images in a continuous W _C When the image satisfies the global brightness average of the image not less than the individual threshold value corresponding to the image and the third brightness difference value of the image is less than a predetermined brightness difference threshold, the image capturing device will operate the current operation. The mode is switched to the day mode, where W _C is an integer and not less than one. The day/night mode switching method of the image capturing device according to claim 2, wherein in the step (c), the value range is a range of 0 to 1, and the upper and lower bounds of the first function value interval are respectively 1- T ₁ and 0, the upper and lower bounds of the second function value interval are respectively T ₂ and 0, and the upper and lower bounds of the third function value interval are 1 and T ₁ , respectively, and the fourth function value interval is upper The bounds and the lower bound are 1 and 1-T ₂ , respectively, wherein T _{1 is} in the range of 0.05 to 0.35, and T _{2 is} in the range of 0.4 to 0.6. The method for switching between day and night modes of the image capturing device according to claim 3, wherein in step (d-1), the individual threshold value is a preliminary reference image having the same third luminance difference value as the image. Global brightness average. The method for switching between day and night modes of the image capturing device according to claim 1, wherein in step (d), the image capturing device determines that the current operating mode is the day mode and that there are consecutive W _C sheets in the images. When the image satisfies the global brightness average of the image being less than a predetermined brightness average threshold, the image capturing device switches the current operating mode to the night mode, where W _C is an integer and not less than 1.