CN102868861B - Obtain the method for image - Google Patents
Obtain the method for image Download PDFInfo
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- CN102868861B CN102868861B CN201110189407.XA CN201110189407A CN102868861B CN 102868861 B CN102868861 B CN 102868861B CN 201110189407 A CN201110189407 A CN 201110189407A CN 102868861 B CN102868861 B CN 102868861B
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Abstract
Obtain a method for image, be applicable to the image acquiring device with photoflash lamp.In this method, preflashing image is obtained when photoflash lamp sends pre-flash.Then, the intensity of main flash of light is estimated.Further, this preflashing image whether overexposure is judged, to calculate overexposure number.Afterwards, brightness contrasting data is inquired about, to downgrade photosensitivity according to overexposure number and brightness target value.And when photoflash lamp sends main flash of light, the photosensitivity after foundation downgrades is to obtain original image.
Description
Technical field
The present invention relates to a kind of method obtaining image, particularly relate to a kind of method of the acquisition image avoiding overexposure phenomenon to produce.
Background technology
General photography be by automatic exposure (Auto Exposure, AE) function to perform exposure computing, allow the brightness that general image reaches desirable.When insufficient light or time for exposure reach below safety shutter, photoflash lamp just will be utilized to compensate brightness, captured image too secretly can not be caused because of brightness cannot identification.
Generally speaking, the main sudden strain of a muscle intensity of digital camera can be estimated according to preflashing image.In order to make the estimation of main sudden strain of a muscle intensity when close-shot more accurate, existing way is as follows: when user switches low coverage pattern, digital camera just reduces preflashing intensity, estimates accurately to allow main sudden strain of a muscle; Or digital camera determines whether shooting at close range according to the information of auto-focusing (Auto Focus, AF), use and switch aperture to reduce light-inletting quantity, and then estimate main sudden strain of a muscle intensity accurately.Or digital camera estimates in-plant main sudden strain of a muscle intensity by the second preflashing.
But, if user does not switch to low coverage pattern and takes near images, main flash of light often can be caused to estimate inaccurate, and obtain overexposure image.In addition, when auto-focusing estimation is inaccurate, can causes and switch aperture time point mistake, if be distant objects, also main flash of light can have been caused to estimate inaccurate, and then produce the problem at dark angle.In addition, although beat secondary pre-flash at one time, can solve low coverage overexposure problem, but if if the intensity of the second pre-flash is too low, photoflash lamp can be made to produce wild effect; If the intensity of the second pre-flash is too high, then can causes the brownout of main flash of light and cannot flash.
Summary of the invention
The invention provides a kind of method obtaining image, the overexposure phenomenon that shooting at close range causes can be avoided.
The present invention proposes a kind of method obtaining image, is applicable to the image acquiring device with photoflash lamp.In this method, preflashing image is obtained when photoflash lamp sends pre-flash.Then, the intensity of main flash of light is estimated.Further, this preflashing image whether overexposure is judged, to calculate overexposure number.Afterwards, brightness contrasting data is inquired about, to downgrade photosensitivity according to overexposure number and brightness target value.And when photoflash lamp sends main flash of light, the photosensitivity after foundation downgrades is to obtain original image.
In one embodiment of this invention, above-mentioned acquisition preflashing image, to calculate in the step of overexposure number, first can be cut into multiple block by preflashing image, more sequentially judges each block whether overexposure, with when judging that wherein a block is as overexposure, and cumulative overexposure number.And judge the step of above-mentioned block whether overexposure, can the average brightness value of each block of sequentially comparison and predetermined luminance value.When the average brightness value of block is greater than predetermined luminance value, just judge that this block is as overexposure.
In one embodiment of this invention, above-mentioned acquisition preflashing image, to calculate in the step of overexposure number, also sequentially can judge multiple pixels in preflashing image whether overexposure, with when judging that wherein a pixel is as overexposure, and cumulative overexposure number.And judge that whether each pixel is the step of overexposure, can the brightness value of each pixel of sequentially comparison and predetermined luminance value.When the brightness value of pixel is greater than predetermined luminance value, judge that this pixel is as overexposure.
In one embodiment of this invention, above-mentioned step of inquiring about brightness contrasting data according to overexposure number and brightness target value, it is that the brightness of taking out corresponding to overexposure number and brightness target value downgrades ratio in brightness contrasting data, to downgrade ratio to downgrade photosensitivity according to this brightness.
In one embodiment of this invention, the step of the intensity of the main flash of light of above-mentioned estimation also can estimate the intensity of main flash of light according to overexposure number and brightness target value.
In one embodiment of this invention, the photosensitivity downgraded in above-mentioned foundation, to after the step obtaining original image, also can calculate the average brightness of original image.Then, calculate the multiplying power that average brightness differs with brightness target value, then adjust the brightness of original image according to this multiplying power.
In one embodiment of this invention, the method for above-mentioned acquisition image also comprises and sets up brightness contrasting data in advance.Such as, by the test pattern that the complete white object of shooting under gray background obtains, estimate that the overexposure number of this test pattern is under the brightness target value of correspondence, the brightness that should downgrade downgrades ratio.
Based on above-mentioned, the present invention judges preflashing image whether overexposure, decides for downgrading how many photosensitivity with the degree according to overexposure.Thus, can under the condition of single pre-flash, the overexposure phenomenon avoiding shooting at close range to cause.
For above-mentioned feature and advantage of the present invention can be become apparent, special embodiment below, and coordinate accompanying drawing to be described in detail below.
Accompanying drawing explanation
Fig. 1 is the method flow diagram according to the acquisition image shown in one embodiment of the invention.
Fig. 2 is according to the preflashing image cutting schematic diagram shown in this case one embodiment.
Reference numeral:
200: preflashing image
201,203,205,207: block
S105 ~ S125: each step of method of the acquisition image of one embodiment of the invention
Embodiment
General photography, when insufficient light or time for exposure reach below safety shutter, can utilize photoflash lamp to compensate brightness.And when shooting at close range, use single pre-flash in preflashing image, easily cause the data obtained incorrect due to hypotelorism, winner is glistened and cannot estimate correctly, and then produce overexposure image.Accordingly, the present invention proposes a kind of method obtaining image, can improve overexposure image under the situation of single pre-flash.In order to make content of the present invention more clear, below especially exemplified by the example that embodiment can be implemented really according to this as the present invention.
Fig. 1 is the method flow diagram according to the acquisition image shown in one embodiment of the invention.In the present embodiment, the method obtaining image can be applied to the image acquiring device (not shown) with processing unit, obtains each step of image to be performed by processing unit.Image acquiring device is such as digital camera or the mobile phone with camera function, but not as limit.
Please refer to Fig. 1, in step S105, obtain preflashing image when photoflash lamp sends pre-flash.Afterwards, in step s 110, the intensity of main flash of light is estimated.Generally speaking, first can send the lower pre-flash of one power to carry out preflashing before sending main flash of light, to judge the reflectivity predicting object by preflashing and automatic exposure parameter, then decide the intensity of main flash of light and the output time of main flash of light according to this.Such as, when user presses shutter, first can go to obtain automatic exposure (AutoExposure, AE) parameter, and obtain preflashing image when photoflash lamp sends pre-flash.Then, according to automatic exposure parameter and preflashing image, the intensity of main flash of light is calculated.Further, more can further according to preflashing image whether overexposure and the brightness target value reached in advance to estimate the intensity of main flash of light.
Then, in step sl 15, preflashing image whether overexposure is judged, to calculate overexposure number.At this, preflashing image can be cut into multiple block.Right time, sequentially judges each block whether overexposure.For example, Fig. 2 is according to the preflashing image cutting schematic diagram shown in this case one embodiment.Please refer to Fig. 2, at this, preflashing image 200 is cut into 16 blocks, is only at this and illustrates, not as limit.Such as, also preflashing image 200 can be cut into 256 blocks in other embodiments.
After preflashing image 200 being cut into multiple block (comprising block 201,203,205 and 207), whether the average brightness value of each block of sequentially comparison is greater than predetermined luminance value.For convenience of description, be described with block 201,203,205 and 207 at this.When the average brightness value of block 201 is greater than predetermined luminance value, just judge that this block 201 is as overexposure.And when judging block 204 as overexposure, just cumulative overexposure number.Then, judge block 203 whether overexposure, then judge block 205 whether overexposure, and judge block 207 whether overexposure, until all blocks all comparison is complete.
In addition, in other embodiments, pixels whole in preflashing image whether overexposure can also sequentially be judged.Such as, whether the brightness value of each pixel of sequentially comparison is greater than predetermined luminance value.When comparison is greater than predetermined luminance value to the brightness value of pixel, then judge that this pixel is as overexposure.Accordingly, judging to when wherein a pixel is as overexposure, just cumulative overexposure number, until all pixels all comparison is complete.
Then, in the step s 120, comparison brightness contrasting data is carried out, to downgrade photosensitivity according to the overexposure number of above-mentioned calculating and brightness target value.For example, brightness contrasting data can be set up in advance in image acquiring device.By the test pattern that the complete white object of shooting under gray background obtains, the overexposure number of estimation test pattern is under the brightness target value of correspondence, and the brightness that should downgrade downgrades ratio.When complete dark, be the wall of 18 degree of ashes, a blank sheet of paper put by wall facing to one side, when distance blank sheet of paper is nearer or zoom ratio is larger, then the area of blank sheet of paper shared by test pattern can uprise, and equals overexposure number and also can uprise.
Suppose that test pattern is cut into 256 blocks, the average brightness when the whole overexposure of 256 blocks is 220, and supposes that brightness target value is 150.If average brightness is downgraded 150 by 220, then photosensitivity can be reduced to 64 by 100, it can thus be appreciated that brightness downgrades ratio be 36%.That is, when overexposure number often increases by 1, the average brightness of test pattern can increase how many, and that estimates photosensitivity by this downgrades ratio.
Accordingly, after establishing brightness contrasting data in advance in image acquiring device, when formally taking, after obtaining preflashing image and calculate overexposure number, just in brightness contrasting data, the brightness of taking out corresponding to overexposure number and brightness target value ratio can be downgraded, to downgrade ratio to downgrade photosensitivity according to brightness.At this, in the process setting up brightness contrasting data, if be test pattern is cut into multiple block to calculate overexposure number, be then also preflashing image is cut into multiple block to judge have several block to be overexposure after obtaining preflashing image.In addition, in the process setting up brightness contrasting data, if be with the pixel of test pattern to calculate overexposure number, be then also each pixel judging preflashing image after obtaining preflashing image whether be that overexposure is to calculate overexposure number.
Finally, in step s 125, when photoflash lamp sends main flash of light, the photosensitivity after foundation downgrades is to obtain original image (raw image).Owing to photosensitivity being downgraded, therefore obtained original image just can be unlikely overexposure.And after acquisition of an original image, the action of brightness fine setting can also be carried out to original image.For example, the average brightness of original image can be calculated.Afterwards, calculate the multiplying power that this average brightness differs with brightness target value, then adjust the brightness of original image according to this multiplying power.
In sum, the present invention calculates overexposure number in preflashing image, obtains the relation of overexposure number and brightness target value, and then acquisition one brightness downgrades ratio to downgrade photosensitivity.Thus, can under the condition of single pre-flash, the overexposure phenomenon avoiding shooting at close range to cause.
Although the present invention with embodiment disclose as above, so itself and be not used to limit the present invention, any person of an ordinary skill in the technical field, when doing a little change and retouching, and does not depart from the spirit and scope of the present invention.
Claims (8)
1. obtain a method for image, be applicable to image acquiring device, wherein this image acquiring device comprises photoflash lamp, and the method comprises:
Preflashing image is obtained when this photoflash lamp sends pre-flash;
Estimate the intensity of main flash of light;
Judge this preflashing image whether overexposure, to calculate overexposure number;
Based on this overexposure number inquiry brightness contrasting data, wherein, this brightness contrasting data comprises this overexposure number brightness under brightness target value and downgrades ratio;
This brightness of taking out in this brightness contrasting data corresponding to this overexposure number downgrades ratio, to downgrade ratio to downgrade photosensitivity according to this brightness; And
When this photoflash lamp sends this main flash of light, this photosensitivity after foundation downgrades, to obtain original image, makes the average brightness of this original image meet this brightness target value.
2. the method for acquisition image according to claim 1, wherein obtains this preflashing image, comprises with the step calculating this overexposure number:
This preflashing image is cut into multiple block;
Sequentially judge above-mentioned multiple block whether overexposure; And
When judge above-mentioned multiple block one of them as overexposure time, this overexposure number cumulative.
3. the method for acquisition image according to claim 2, wherein sequentially judges that the step of above-mentioned multiple block whether overexposure comprises:
The respective average brightness value of the above-mentioned multiple block of sequentially comparison and predetermined luminance value; And
When one of them average brightness value of above-mentioned multiple block is greater than this predetermined luminance value, judge that this block is as overexposure.
4. the method for acquisition image according to claim 1, wherein obtains this preflashing image, comprises with the step calculating this overexposure number:
Sequentially judge multiple pixels in this preflashing image whether overexposure; And
When judge above-mentioned multiple pixel one of them as overexposure time, this overexposure number cumulative.
5. the method for acquisition image according to claim 4, wherein sequentially judges that the step of above-mentioned multiple pixel in this preflashing image whether overexposure comprises:
The respective brightness value of the above-mentioned multiple pixel of sequentially comparison and predetermined luminance value; And
When one of them brightness value of above-mentioned multiple pixel is greater than this predetermined luminance value, judge that this pixel is as overexposure.
6. the method for acquisition image according to claim 1, wherein estimate that the step of the intensity of this main flash of light comprises:
The intensity of this main flash of light is estimated according to this overexposure number and this brightness target value.
7. the method for acquisition image according to claim 1, wherein according to this photosensitivity of downgrading to after the step obtaining this original image, also comprise:
Calculate the average brightness of this original image;
Calculate the multiplying power that this average brightness differs with this brightness target value; And
The brightness of this original image is adjusted according to this multiplying power.
8. the method for acquisition image according to claim 1, wherein also comprises:
Set up this brightness contrasting data, comprising:
By the test pattern that the complete white object of shooting under gray background obtains, estimate that the overexposure number of this test pattern is under the brightness target value of correspondence, the brightness that should downgrade downgrades ratio.
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| CN201110189407.XA CN102868861B (en) | 2011-07-07 | 2011-07-07 | Obtain the method for image |
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| CN102868861B true CN102868861B (en) | 2015-08-05 |
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| CN107566752B (en) * | 2017-10-31 | 2020-08-11 | 努比亚技术有限公司 | Shooting method, terminal and computer storage medium |
| CN110830728A (en) * | 2018-08-13 | 2020-02-21 | 浙江宇视科技有限公司 | Exposure adjusting method and device |
| CN110187591B (en) * | 2019-05-07 | 2021-09-17 | Oppo广东移动通信有限公司 | Flash lamp control method and device, electronic equipment and storage medium |
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| CN100568926C (en) * | 2006-04-30 | 2009-12-09 | 华为技术有限公司 | The preparation method of automatic exposure control parameter and control method and imaging device |
| JP4791331B2 (en) * | 2006-11-15 | 2011-10-12 | 富士フイルム株式会社 | Imaging apparatus and exposure control method |
| CN101516002A (en) * | 2008-02-18 | 2009-08-26 | 佛山普立华科技有限公司 | Camera and method for adjusting flash |
| CN101751575B (en) * | 2008-12-19 | 2012-12-19 | 鸿富锦精密工业（深圳）有限公司 | Image comparison system and method |
| TWI401522B (en) * | 2008-12-31 | 2013-07-11 | Altek Corp | Flash intensity adjustment method |
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