TWI390965B - Method for stimulating the depth of field of an image - Google Patents

Description

Shallow depth of field simulation method for digital image

The invention relates to a shallow depth of field simulation method for digital images, in particular to a shallow depth of field simulation method for adjusting the blur degree of an area image according to the difference between the shooting focal length of each region image and the optimal focal length of the main body.

In general, when a digital camera performs a shooting action, the digital camera adjusts the relative position of its lens group so that the focus point can fall on the subject being photographed. In this way, the captured digital image (or digital photo) can clearly display the subject. The scene in the distance between the front and the back of the subject is not completely in focus, but because it is not far from the focus, it can be clearly displayed in the digital image. The distance range is the so-called depth of field (Depth of Field). Scenes outside the depth of field are blurred because they are far from the focus, and cannot be clearly displayed.

The depth of field depth can be determined by multiple shooting parameters of the digital camera. For example, the longer the focal length of the lens group (such as the telescope head), the shallower the depth of field; the closer the object distance (distance between the lens group and the subject), the shallower the depth of field And the larger the aperture, the shallower the depth of field. The user usually changes the depth of the depth of field by adjusting the aperture of the digital camera.

The depth of field depth can affect the look and feel of digital images. Different scenes are suitable for shooting situations. For example, when shooting portraits, shallow depth of field is usually used, so that the entire digital image can be replaced by the subject (portrait). Clearly showing that the rest of the scene is blurred. This gives a beautiful visual aesthetic and can highlight the existence of the subject; while shooting a natural landscape will make the depth of field as long as possible, so that all the scenes of such digital images can be clearly displayed.

Although the depth of field depth can be adjusted by the aperture value, except for the Digital Single Lens Reflex (DSLR) camera, which has a wide range of aperture values for adjustment, the aperture range of a relatively inexpensive digital camera is not adjusted. Therefore, it is difficult to take a digital image with a shallow depth of field effect.

Therefore, only the retouch method of some images or photos can be used to achieve the shallow depth of field effect. "System for stimulating the depth of field of an image in two dimensional space and method of operation", which is provided by the system, which is provided by the US Patent No. 6,148,113. After the user takes a digital image, the focus position of the digital image is selected, and then the system "defocuss" the pixel according to the distance of each pixel of the digital image from the focus position. For example, if the focus position is in the center of the digital image, the scene at the corner of the digital image will be closer to the center and the scene will be blurred and unclear. In addition to the above methods, many commercial image processing software on the market can achieve similar effects.

However, these digital images with shallow depth of field through post-production have some missing as follows: Since the post-production methods determine the degree of blurring according to the "plane distance" between the pixel and the focus in the digital image, it is not based on the actual shooting. "Focus distance" to determine the degree of blurring, Therefore, the effect of shallow depth of field is often inappropriate. For example, the scene at the corner and the scene in the center actually have the same focal length, but the scene at the corner is seriously blurred.

Although some image processing software allows the user to set the depth of field effect of different areas of the digital image, the user can adjust the depth of field effect according to the focus distance of the digital image and the focus (main body). However, this method is time consuming and laborious, and it is difficult for the user to know the difference in the true focusing distance between each scene and the focus, so the method is still somewhat missing, which is a pity.

On the contrary, the present inventors felt that the above-mentioned deletion could be improved, and therefore proposed a present invention which is rational in design and effective in improving the above-mentioned deficiency.

The main object of the present invention is to provide a shallow depth of field simulation method for digital images, which determines the degree of blurring according to the difference between the shooting focal length of each region image in the digital image and the optimal focal length of the subject, thereby obtaining a shallow depth of field effect. Natural digital imagery.

To achieve the above object, the present invention provides a shallow depth of field simulation method for digital images, comprising the steps of: providing a photographing device that focuses on a subject; obtaining a best focal length of the subject, and capturing a digital image; The digital image is divided into a plurality of regional images; the shooting focal lengths of the regional images are analyzed; and the regional images are blurred, and the blurring degree is adjusted according to the difference between the shooting focal lengths of the regional images and the optimal focal length.

Therefore, the shallow depth of field simulation method of the digital image of the present invention has the following beneficial effects: the focal length of the image of each region in the digital image It is analyzed that the image of the area can be blurred according to the difference between the shooting focal length and the best focal length of the image of the area. In this way, the simulated shallow depth of field effect is more natural, and there is no case where the shooting distance is similar, but the degree of blurring is very different. Or, conversely, the shooting distance is very far, but the degree of blurring is similar.

The detailed description and drawings of the present invention are to be understood as the

Referring to the first to third figures, the present invention provides a shallow depth of field simulation method for digital images, which has the following steps:

Step S100: First, a photographing device 10 is provided. The camera device 10 has a processor 11, a lens group 12, a photosensitive element 13, and a storage module 14. The photographing device 10 can capture an image of a scene facing the lens group 12 and capture a digital image 40 (as shown in FIG. 5). The photographing device 10 can be a digital camera, a camera-enabled mobile phone, etc., and the present embodiment takes a digital camera as an example. The hardware specifications of the imaging device 10 are not limited, for example, the adjustment range of the aperture.

Step S102: Referring to the third figure, the user then decides the scene to be photographed, for example, the scene of the embodiment is three balloons 21. It is also determined which of the scenes is the main object 20 of the photographing. For example, in the present embodiment, the middle balloon 21 is used as the main body 20. Next, the lens group 12 of the imaging device 10 is directed toward the main body 20, to the main The body 20 performs the process of focusing. During the focusing process, the photographing device 10 changes the distance between the lens group 12 and the photosensitive member 13 therein several times to change the focal length (the position of the focus) of the photographing device 10.

Each time the focal length is changed, the camera 10 captures a reference digital image, which can be stored in the storage module 14. Then, the processor 11 further analyzes the reference digital images to determine which of the reference digital images has the most clear image of the main body 20. Referring to the fourth figure, for example, the image of the main body 20 of the reference digital image 30 is not clear, so the focal length used for capturing the reference digital image 30 is not the preferred focal length D1 of the subject 20 . The lens group 12 needs to continue moving.

The method of judging the degree of image clarity may be a common autofocus method such as a contrast detection method, and is not limited thereto. The resolution of the reference digital image 30 is typically low in order to reduce the computational time spent by the processor 11 in the analysis.

Step S104: After the focus program is passed, the photographing device 10 can find the best focal length D1 of the subject 20 so that the image of the main body 20 can approach or fall on the photosensitive element 13. Referring to the fifth figure, the camera 10 then captures the subject 20 and its nearby scenes into a digital image 40 having a higher resolution (compared to the reference digital image 30). At this time, the shallow depth of field effect of the digital image 40 is less obvious, and the degree of clarity of the main body 20 (the central balloon 21) and other scenes (the balloons 21 on both sides) are not significantly different.

Step S106: Next, referring to the sixth figure, the digital image 40 is divided into a plurality of area images 41. The size of the area image 41 is determined by the number of pixels it has. If the area image 41 is small, the digital image 40 can distinguish a plurality of area images 41. In this embodiment, the digital image 40 is equally divided into 16 area images 41.

Step S108: After that, the analysis of the shooting focal lengths of the regional images 41 is started, and it is inferred that if a certain regional image 41 is to be clearly photographed, the focal length of the imaging device 10 should be. Referring to the second and third figures, for example, when the area image 41 of the balloon 21 on both sides of the digital image 40 is to be clearly photographed, the focal length of the photographing device 10 should be D2 and D3, and the values of D2 and D3 are the area. The focal length of the image 41.

Please refer to the seventh figure, the detailed steps of "Analyzing the focal length of the image of the area 41" are as follows:

Step S200: The foregoing step S102 mentions that the photographing device 10 captures a reference digital image 30 every time the focal length is adjusted during the focusing process. Therefore, the reference digital images 30 each have a corresponding shooting focal length.

Step S202: Next, referring to the eighth figure, each of the reference digital images 30 is also divided into a plurality of area images 31. The number of the area images 31 of each of the reference digital images 30 coincides with the number of the area images 41 of the digital image 40, which is also 16.

Step S204: After that, the analysis of the regional images 31 of each of the reference digital images 30 is started. Judging whether the area image 31 is located according to the sharpness of each area image 31 The corresponding focal length of the reference digital image 30 is corresponding. For example, if the area image 31 in the upper left is the most clear in a certain reference digital image 30, the shooting focal length is the shooting focal length of the reference digital image 30. In this way, the shooting focal length of each of the area images 31 can be inferred, and the shooting focal length of the area image 31 is equal to the shooting focal length of the area image 41 of the digital image 40.

Step S206: After all the area images 41 are inferred, the area images 41 may be further sorted according to the length of the shooting focal length. Please refer to the ninth figure, or further make a distance map, and mark the focal length of each area image 41 on the area image 41. In this way, the relative length of the shooting focal length of the area image 41 can be clearly understood. It is also possible to mark the difference between the shooting focal length of each of the area images 41 and the optimum focal length in the area image 41 to form another distance distribution map (not shown).

Step S110: Finally, the processor 11 blurs the area image 41 of the digital image 40 portion, so that the digital image 40 has a distinct shallow depth of field effect. The degree of blurring of the area images 41 is adjusted according to the difference between the shooting focal length of the area image 41 and the optimal focal length. If the difference is larger, the degree of blurring is larger, and the degree of blurring of the area image 41 of the same photographing focal length is the same. In this embodiment, a Gaussian blur is used to blur the area images 41. Moreover, by changing the Gaussian radius value of the Gaussian blur method, the degree of blurring of the area images 41 can be adjusted.

In addition, the following method can also be used to blur the regional image 41 of the digital image 40 portion:

First, the size of the reference digital image 30 is enlarged to match the size of the digital image 40. The resolution of the reference digital image 30 is low, so that the reference digital image 30 becomes blurred after being enlarged.

Then, the partial area image 41 of the digital image 40 is added to and merged with the corresponding area image 31 of one of the reference digital images 30. Since the area image 31 is relatively blurred, the area image 41 is also blurred as compared with the area image 41. The area images 41 of different shooting focal lengths are combined using the area images 31 of the different reference digital images 30.

In summary, the shallow depth of field simulation method of the digital image of the present invention has the following effects: the shooting focal length of each region image 41 in the digital image 40 can be analyzed, so that the difference between the shooting focal length and the optimal focal length of the regional image 41 can be used. Blur the area images 41. In this way, the simulated shallow depth of field effect is more natural, and there is no case where the shooting distance is similar, but the degree of blurring is very different. Or, conversely, the shooting distance is very far, but the degree of blurring is similar.

The above is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Therefore, the equivalents of the present invention and the equivalents of the drawings are all included in the present invention. Within the scope of protection, it is given to Chen Ming.

10‧‧‧Photographing device

11‧‧‧ Processor

12‧‧‧ lens group

13‧‧‧Photosensitive elements

14‧‧‧Storage module

20‧‧‧ Subject

21‧‧‧ balloons

30‧‧‧Digital imagery

31‧‧‧Area image

40‧‧‧Digital imagery

41‧‧‧Area image

Steps S100 to S110

Steps S200 to S206

The first figure is a functional block diagram of a photographing apparatus for a shallow depth of field simulation method of the digital image of the present invention.

The second figure is a flow of a shallow depth of field simulation method of the digital image of the present invention. Cheng Tu.

The third figure is a schematic diagram of a shooting scene of a shallow depth of field simulation method of the digital image of the present invention.

The fourth figure is a schematic diagram of a reference digital image of the shallow depth of field simulation method of the digital image of the present invention.

The fifth figure is a schematic diagram of a digital image of a shallow depth of field simulation method of the digital image of the present invention.

The sixth figure is a schematic diagram of a regional image of a digital image of a shallow depth of field simulation method of the digital image of the present invention.

The seventh figure is a flow chart of the focal length analysis of the area image of the shallow depth of field simulation method of the digital image of the present invention.

The eighth figure is a schematic diagram of the regional image of the reference digital image of the shallow depth of field simulation method of the digital image of the present invention.

The ninth figure is a schematic diagram of the focal length distribution of the regional image of the shallow depth of field simulation method of the digital image of the present invention.

Steps S100 to S110

Claims (9)

A shallow depth of field simulation method for digital images, comprising the steps of: providing a photographing device that focuses on a subject; obtaining a best focal length of the subject, and capturing a digital image; dividing the digital image into a plurality of proportions The area image; analyzing the shooting focal length of the image of the area; and blurring the image of the area, and adjusting the degree of blur according to the difference between the shooting focal length of the area image and the optimal focal length. The shallow depth of field simulation method of the digital image according to the first aspect of the patent application, wherein the step of “analyzing the focal length of the image of the region” further includes the following steps: the camera captures a plurality of reference digits during the focusing process. Image, the reference digital images each have a corresponding shooting focal length; the reference digital images are divided into a plurality of regional images; respectively, the regional images of the reference digital images are separately analyzed; and whether the regional images are separately determined The shooting focal length of the corresponding reference digital image. The shallow depth of field simulation method of the digital image according to the second aspect of the patent application, wherein in the step of “analyzing the focal length of the image of the area”, determining whether the image of the area is located according to the degree of clarity of the image of the area Corresponding shooting focal length of the reference digital image. The shallow depth of field simulation method of the digital image described in claim 2, wherein the step of "analyzing the focal length of the image of the region" includes the following steps: The regional images are sorted according to the shooting focal length of the regional images. A shallow depth of field simulation method for digital images according to claim 2, wherein the resolution of the reference digital images is lower than the resolution of the digital images. The shallow depth of field simulation method of the digital image according to claim 5, wherein the photographing device has a storage module, and the reference digital images are stored in the storage module. The shallow depth of field simulation method of the digital image according to claim 6 , wherein the step of “blurring the image of the area” further comprises the steps of: magnifying the size of the reference digital image to the digital image The size of the image of the digital image is merged with the corresponding image of the area of the digital image, so that the image of the area of the digital image is blurred. A shallow depth of field simulation method for digital images according to claim 1, wherein in the step of "blurring the regional images", a Gaussian blur method is used to blur the regional images of the digital image. For example, in the shallow depth of field simulation method of the digital image according to Item 8 of the patent application, in the step of “blurring the image of the area”, the Gaussian radius of the Gaussian blur method is changed to adjust the blur degree of the image of the area.