CN102868861A - Method for acquiring images - Google Patents
Method for acquiring images Download PDFInfo
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- CN102868861A CN102868861A CN201110189407XA CN201110189407A CN102868861A CN 102868861 A CN102868861 A CN 102868861A CN 201110189407X A CN201110189407X A CN 201110189407XA CN 201110189407 A CN201110189407 A CN 201110189407A CN 102868861 A CN102868861 A CN 102868861A
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- overexposure
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Abstract
The invention discloses a method for acquiring images, which is applicable to an image acquisition device with a flash lamp. The method comprises the following steps: acquiring a pre-flashing image when the flash lamp emits pre-flashing light; then, estimating the intensity of main flash, and judging whether the pre-flashed image is in overexposure so as to calculate the number of the overexposure; later, inquiring the brightness contrasting data so as to regulate down photosensitivity according to the number of the overexposure and the target brightness data. When the flash lamp emits main flash, the original image can be acquired according to the photosensitivity regulated down.
Description
Technical field
The present invention relates to a kind of method of obtaining image, relate in particular to a kind of method of obtaining image of avoiding the overexposure phenomenon to produce.
Background technology
General photography is to carry out the exposure computing by automatic exposure (Auto Exposure, AE) function, allows general image reach desirable brightness.Reach safety shutter when following when insufficient light or time for exposure, just will utilize photoflash lamp that compensation is done in brightness so that captured image can too secretly not cause because of brightness can't identification.
Generally speaking, the main intensity of dodging of digital camera can be estimated according to the preflashing image.Main to dodge the estimation of intensity when the close-shot more accurate in order to allow, and existing way is as follows: when the user was switched the low coverage pattern, digital camera just reduced preflashing intensity, to allow main the sudden strain of a muscle estimate accurately; Perhaps, digital camera determines whether shooting at close range according to the information of automatically focusing (Auto Focus, AF), uses the switching aperture and reduces light-inletting quantity, and then estimate the accurately main intensity of dodging.Perhaps, digital camera estimates the in-plant main intensity of dodging by the second preflashing.
Yet, if the user does not switch to the low coverage pattern and takes the low coverage image, often can cause main flash of light estimation inaccurate, and obtain the overexposure image.In addition, when the focusing estimation is inaccurate automatically, can causes and switch aperture time point mistake, if be the long distance object, it is inaccurate also can to have caused main flash of light to estimate, and then produces the problem at dark angle.In addition, though beat at one time the secondary pre-flash, low coverage overexposure problem solved, if but if the second preflashing light intensity is excessively low, and meeting is so that photoflash lamp produces wild effect; If the second preflashing light intensity is too high, then can causes the brownout of main flash of light and can't flash.
Summary of the invention
The invention provides a kind of method of obtaining image, the overexposure phenomenon that can avoid shooting at close range to cause.
The present invention proposes a kind of method of obtaining image, is applicable to have the image acquiring device of photoflash lamp.In the method, when sending pre-flash, obtains by photoflash lamp the preflashing image.Then, the intensity of the main flash of light of estimation.And, judge whether overexposure of this preflashing image, to calculate the overexposure number.Afterwards, according to overexposure number and brightness target value inquiry brightness contrasting data, to downgrade photosensitivity.And when photoflash lamp sends main flash of light, obtain original image according to the photosensitivity after downgrading.
In one embodiment of this invention, the above-mentioned preflashing image that obtains in the step of calculating the overexposure number, can be cut into a plurality of blocks with the preflashing image first, sequentially judges whether overexposure of each block again, and with when judging that wherein a block is as overexposure, the overexposure number adds up.And judge the whether step of overexposure of above-mentioned block, can sequentially compare average brightness value and the default brightness value of each block.When the average brightness value of block during greater than default brightness value, judge that just this block is overexposure.
In one embodiment of this invention, the above-mentioned preflashing image that obtains in the step of calculating the overexposure number, also can sequentially be judged a plurality of pixels overexposure whether in the preflashing image, and with when judging that wherein a pixel is as overexposure, the overexposure number adds up.And judge whether each pixel is the step of overexposure, can sequentially compare brightness value and the default brightness value of each pixel.When the brightness value of pixel during greater than default brightness value, judge that this pixel is overexposure.
In one embodiment of this invention, above-mentioned step according to overexposure number and brightness target value inquiry brightness contrasting data, it is to take out the overexposure number and the corresponding brightness of brightness target value downgrades ratio in the brightness contrasting data, downgrades photosensitivity to downgrade ratio 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 be estimated according to overexposure number and brightness target value the intensity of main flash of light.
In one embodiment of this invention, after the photosensitivity that above-mentioned foundation downgrades is obtained the step of original image, also can calculate the average brightness of original image.Then, calculate the multiplying power that average brightness and brightness target value differ, adjust again the brightness of original image according to this multiplying power.
In one embodiment of this invention, the above-mentioned method of obtaining image also comprises and sets up in advance the brightness contrasting data.For example, by the test pattern that the complete white object of shooting under gray background obtains, estimate the overexposure number of this test pattern under the brightness target value of correspondence, the brightness that should downgrade downgrades ratio.
Based on above-mentioned, the present invention judges whether overexposure of preflashing image, decides to want to downgrade how many photosensitivity with the degree of foundation overexposure.Thus, can be under the condition of single pre-flash, the overexposure phenomenon of avoiding shooting at close range to cause.
For above-mentioned feature and advantage of the present invention can be become apparent, embodiment cited below particularly, and cooperate accompanying drawing to be described in detail below.
Description of drawings
Fig. 1 is according to the method flow diagram that obtains image shown in one embodiment of the invention.
Fig. 2 is according to the cutting of the preflashing image shown in this case one embodiment schematic diagram.
Reference numeral:
200: the preflashing image
201,203,205,207: block
S105～S125: each step of the method for obtaining image of one embodiment of the invention
Embodiment
General photography reaches safety shutter when following in insufficient light or time for exposure, can utilize photoflash lamp that compensation is done in brightness.And when shooting at close range, use single pre-flash in the preflashing image, to cause easily the data obtained incorrect owing to hypotelorism, the winner is glistened can't estimate correctly, and then produce the overexposure image.Accordingly, the present invention proposes a kind of method of obtaining image, can improve the overexposure image under the situation of single pre-flash.In order to make content of the present invention more clear, below the example that really can implement according to this as the present invention especially exemplified by embodiment.
Fig. 1 is according to the method flow diagram that obtains image shown in one embodiment of the invention.In the present embodiment, the method for obtaining image can be applied to the image acquiring device (not shown) with processing unit, obtains each step of image to be carried out by processing unit.Image acquiring device for example is digital camera or the mobile phone with camera function, but not as limit.
Please refer to Fig. 1, in step S105, when photoflash lamp sends pre-flash, obtain the preflashing image.Afterwards, in step S110, the intensity of the main flash of light of estimation.Generally speaking, before sending main flash of light, can send first one lower pre-flash of power and carry out preflashing, to judge the reflectivity of predicting object by preflashing and automatic exposure parameter, decide according to this again the intensity of main flash of light and the output time of main flash of light.For example, when the user presses shutter, can reach first to get automatic exposure (Auto Exposure, AE) parameter, and when photoflash lamp sends pre-flash, obtain the preflashing image.Then, according to automatic exposure parameter and preflashing image, calculate the intensity of main flash of light.And, more can be further overexposure and the brightness target value reached are in advance estimated the intensity of main flash of light according to the preflashing image.
Then, in step S115, judge whether overexposure of preflashing image, to calculate the overexposure number.At this, the preflashing image can be cut into a plurality of blocks.The right time sequentially judged whether overexposure of each block.For instance, Fig. 2 is according to the cutting of the preflashing image shown in this case one embodiment schematic diagram.Please refer to Fig. 2, at this preflashing image 200 be cut into 16 blocks, at this only for illustrating, not as limit.For example, also preflashing image 200 can be cut into 256 blocks in other embodiments.
Preflashing image 200 is being cut into a plurality of blocks (comprising block 201,203,205 and 207) afterwards, whether is sequentially comparing the average brightness value of each block greater than default brightness value.For convenience of description, describe with block 201,203,205 and 207 at this.When the average brightness value of block 201 during greater than default brightness value, judge that just this block 201 is overexposure.And when judging block 204 as overexposure, the overexposure number just adds up.Then, judge whether overexposure of block 203, then judge whether overexposure of block 205, and judge whether overexposure of block 207, until all blocks have all been compared.
In addition, in other embodiments, also can sequentially judge whether overexposure of pixels whole in the preflashing image.For example, whether sequentially compare the brightness value of each pixel greater than default brightness value.When comparison during greater than default brightness value, judges then that this pixel is overexposure to the brightness value of pixel.Accordingly, judging when wherein a pixel is as overexposure that just cumulative overexposure number is until all pixels have all been compared.
Then, in step S120, compare the brightness contrasting data according to overexposure number and the brightness target value of above-mentioned calculating, to downgrade photosensitivity.For instance, can in image acquiring device, set up in advance the brightness contrasting data.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 walls of 18 degree ashes facing to one side, put a blank sheet of paper at wall, when nearer or zoom ratio was larger when the distance blank sheet of paper, then blank sheet of paper shared area in test pattern can uprise, and equals the overexposure number and also can uprise.
Suppose that test pattern is cut into 256 blocks, the average brightness when 256 whole overexposures of block is 220, and the hypothesis brightness target value is 150.If average brightness is downgraded 150 by 220, then photosensitivity can be reduced to 64 by 100, and brightness that hence one can see that downgrades ratio and is 36%.That is to say during the every increase by 1 of overexposure number, how many average brightness of test pattern can increase, estimate by this ratio that downgrades of photosensitivity.
Accordingly, after in image acquiring device, establishing the brightness contrasting data in advance, when formally taking, after obtaining the preflashing image and calculating the overexposure number, just can in the brightness contrasting data, take out the overexposure number and the corresponding brightness of brightness target value downgrades ratio, downgrade ratio with foundation brightness and downgrade photosensitivity.At this, in the process of setting up the brightness contrasting data, if be test pattern to be cut into a plurality of blocks calculate the overexposure number, then also be the preflashing image to be cut into a plurality of blocks judge that it is overexposure that several blocks are arranged after obtaining the preflashing image.In addition, in the process of setting up the brightness contrasting data, if be to calculate the overexposure number with the pixel of test pattern, then also be to judge whether each pixel of preflashing image is that overexposure is to calculate the overexposure number after obtaining the preflashing image.
At last, in step S125, when photoflash lamp sends main flash of light, obtain original image (raw image) according to the photosensitivity after downgrading.Owing to photosensitivity is downgraded, the original image that therefore obtains just can be unlikely overexposure.And after obtaining original image, can also carry out to original image the action of brightness fine setting.For instance, can calculate the average brightness of original image.Afterwards, calculate the multiplying power that this average brightness and brightness target value differ, adjust again the brightness of original image according to this multiplying power.
In sum, the present invention calculates the overexposure number in the preflashing image, obtain the relation of overexposure number and brightness target value, and then obtains a brightness and downgrade ratio and downgrade photosensitivity.Thus, can be under the condition of single pre-flash, the overexposure phenomenon of avoiding shooting at close range to cause.
Although the present invention discloses as above with embodiment, so it is not to limit the present invention, and any person of an ordinary skill in the technical field when can doing a little change and retouching, and does not break away from the spirit and scope of the present invention.
Claims (9)
1. a method of obtaining image is applicable to image acquiring device, and wherein this image acquiring device comprises photoflash lamp, and the method comprises:
When sending pre-flash, obtains by this photoflash lamp the preflashing image;
The intensity of the main flash of light of estimation;
Judge whether overexposure of this preflashing image, to calculate the overexposure number;
According to this overexposure number and brightness target value inquiry brightness contrasting data, to downgrade photosensitivity; And
When this photoflash lamp sends this master's flash of light, obtain original image according to this photosensitivity after downgrading.
2. the method for obtaining image according to claim 1 is wherein obtained this preflashing image, comprises with the step of calculating this overexposure number:
This preflashing image is cut into a plurality of blocks;
Sequentially judge whether overexposure of those blocks; And
When judge those blocks one of them during as overexposure, cumulative this overexposure number.
3. the method for obtaining image according to claim 2, wherein sequentially judge those blocks whether the step of overexposure comprise:
Sequentially compare those blocks average brightness value and default brightness value separately; And
When one of them average brightness value of those blocks during greater than this default brightness value, judge that this block is overexposure.
4. the method for obtaining image according to claim 1 is wherein obtained this preflashing image, comprises with the step of calculating this overexposure number:
Sequentially judge a plurality of pixels overexposure whether in this preflashing image; And
When judge those pixels one of them during as overexposure, cumulative this overexposure number.
5. the method for obtaining image according to claim 4, wherein sequentially judge in this preflashing image those pixels whether the step of overexposure comprise:
Sequentially compare those pixels brightness value and default brightness value separately; And
When one of them brightness value of those pixels during greater than this default brightness value, judge that this pixel is overexposure.
6. the method for obtaining image according to claim 1 wherein comprises according to the step that this overexposure number and this brightness target value are inquired about this brightness contrasting data:
This overexposure number of taking-up and the corresponding brightness of this brightness target value downgrade ratio in this brightness contrasting data, downgrade this photosensitivity to downgrade ratio according to this brightness.
7. the method for obtaining image according to claim 1, estimate that wherein the step of the intensity of this master's flash of light comprises:
Estimate the intensity of this master's flash of light according to this overexposure number and this brightness target value.
8. the method for obtaining image according to claim 1 wherein after obtaining the step of this original image according to this photosensitivity that downgrades, also comprises:
Calculate the average brightness of this original image;
Calculate the multiplying power that this average brightness and this brightness target value differ; And
Adjust the brightness of this original image according to this multiplying power.
9. the method for obtaining 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 the overexposure number of this test pattern 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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| CN201110189407.XA CN102868861B (en) | 2011-07-07 | 2011-07-07 | Obtain the method for image |
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| CN107566752A (en) * | 2017-10-31 | 2018-01-09 | 努比亚技术有限公司 | A kind of image pickup method, terminal and computer-readable storage medium |
| CN110187591A (en) * | 2019-05-07 | 2019-08-30 | Oppo广东移动通信有限公司 | Flash lamp control method, device, electronic equipment and 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 |
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| CN110830728A (en) * | 2018-08-13 | 2020-02-21 | 浙江宇视科技有限公司 | Exposure adjusting method and device |
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| CN102868861B (en) | 2015-08-05 |
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