CN1316818C - Image contrast intensifying method - Google Patents
Image contrast intensifying method Download PDFInfo
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- CN1316818C CN1316818C CNB2005100659293A CN200510065929A CN1316818C CN 1316818 C CN1316818 C CN 1316818C CN B2005100659293 A CNB2005100659293 A CN B2005100659293A CN 200510065929 A CN200510065929 A CN 200510065929A CN 1316818 C CN1316818 C CN 1316818C
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- 238000000034 method Methods 0.000 title claims abstract description 33
- 230000007704 transition Effects 0.000 claims description 13
- 238000013507 mapping Methods 0.000 claims description 11
- 238000010606 normalization Methods 0.000 claims description 7
- 230000010354 integration Effects 0.000 claims description 6
- 230000002787 reinforcement Effects 0.000 abstract description 6
- 238000006243 chemical reaction Methods 0.000 abstract description 4
- 238000009825 accumulation Methods 0.000 abstract 1
- 230000003014 reinforcing effect Effects 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 11
- 230000000694 effects Effects 0.000 description 5
- 238000012546 transfer Methods 0.000 description 5
- 230000003044 adaptive effect Effects 0.000 description 2
- 230000008034 disappearance Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 238000012549 training Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
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Abstract
The present invention relates to an image contrast reinforcing method. In the method, a sheet of image is scanned to calculate a brightness difference value of two adjacent pixels in the image in sequence; next, the value is judged whether to be larger than a predetermined threshold value, if true, then generate a positive force sequence according to the two brightness values, if false, then generate a negative force sequence; generation calculations and accumulation calculations of the positive force sequence and the negative force sequence are always repeatedly operated to obtain a net positive force sequence and a net negative force sequence until the judgement is ended; then, the net positive force sequence subtracts the net negative force sequence added with weight to become a net force sequence and to integrate and normalize so as to obtain an expansionary force function to do linear combination with an original brightness conversion function; a new brightness conversion function is obtained to adjust a brightness value of an original image to reinforce image contrast. Two force sequences in different forms are also put forward; if the force sequences can be used as the base of contrast reinforcement, then cost desired by calculating the negative force sequence can be omitted. The present invention can also simultaneously prevent noises from amplifying and images from being unnatural.
Description
Technical field
The present invention relates to a kind of image contrast and add strong method, particularly a kind of avoid improving image noise and improve the factitious image contrast of image add strong method.
Background technology
Light source has very significant effects when image forms, when imaging environment is crossed bright or be dark excessively, the image that is captured will be the image of a low contrast usually.In order to improve image contrast, a basic skills commonly used is histogram equalization (Histogram Equalization).When obtaining the brightness histogram of an image, can obtain a luminance transfer function according to histogram information, and do the adjustment of image brilliance, in the hope of reaching good image contrast quality with this function.The basic concepts of histogram equalization are to specify GTG value in a big way to give the higher GTG value of histogram intermediate value.Yet this method can cause trickleer part contrast to lose, improve undesired image noise and cause the unnatural of image.
Y.T.Kim published thesis in 1997: the paper that people such as " Contrast Enhancement Using BrightnessPreserving Bi-Histogram Equalization " and K.Wongsritong delivered in 1998: " Contrast Enhancement Using Multipeak Histogram Equalization WithBrightness Preserving ", thinking the factitious image that histogram equalization method is produced, may be because the change of image average brightness value before and after handling.Therefore they have proposed some modes and have tried to improve this problem.Yet if the image average brightness value does not change the preservation that can not guarantee the image naturality before and after making processing, because except brightness value, the information of object also is considerable in the color information of image or the image.
In addition, the paper that people such as J.Y.Kim delivered in calendar year 2001: the paper that people such as " An Advanced ContrastEnhancement Using Partially Overlapped Sub-Block Histogram Equalization " and T.K.Kim delivered in 1998: " Contrast Enhancement SystemUsing Spatially Adaptive Histogram Equalization with Electronics ", the method that proposes a kind of regional histogram equalization is to improve contrast, yet the method that they proposed still has quite high complexity on calculating.
Also have, the paper that people such as S.Sakaue delivered in nineteen ninety-five: " Dynamic Range Expansionof Video Cameras by Adaptive Gamma Processing " proposes to utilize a neuroid to improve image contrast, but training data (training data) and decision rule (decision rules) may also can influence quality, therefore also can't effectively improve the contrast quality.
In view of this, the present invention is directed to the defective that exists in the above-mentioned prior art, propose a kind of image contrast and add strong method, to improve above-mentioned disappearance.
Summary of the invention
Main purpose of the present invention, aim to provide a kind of image contrast and add strong method, it is to utilize the positive force sequence to improve image contrast, and utilizes the opposite force sequence to avoid noise to amplify, and utilize the clean power sequence of a mapping functional value adjustment, with the not natural vision effect of avoiding excessively reinforcement to cause.
For achieving the above object, the present invention proposes a kind of image contrast and adds strong method, comprise an image at first is provided, and scan this image to calculate the value of adjacent two pixel intensity differences in the image, whether the value of judging this difference again is greater than a default threshold value, if, then produce a positive force sequence according to corresponding monochrome information, if not, then produce a negative force sequence according to this two brightness value, the generation of positive force sequence and negative force sequence and accumulating operation will repeat running always and be clean positive force sequence and clean negative force sequence, till checking all pixel information of importing image, then clean positive force sequence is deducted the clean negative force sequence that adds weight, become a clean power sequence, follow the clean power sequence of integration, and with integrated value normalization at 0 to 255, to obtain an expansionary force function, at last expansionary force function and original brightness transfer function are carried out linear combination, and obtain a new brightness transition function, and adjust the brightness value of raw video with this function, to obtain contrasting the image of reinforcement.In addition, in order to lower hardware burden and cost, the present invention has further proposed two kinds of multi-form power sequences (form one and form two), as if the basis of strengthening as a comparison with this power sequence, can further save and calculate the required cost of negative force sequence.
For the effect that makes purpose of the present invention, technology contents, characteristics and realized is more readily understood, describe specific embodiment in detail below in conjunction with accompanying drawing.
Description of drawings
Fig. 1 is a flow chart of the present invention.
Fig. 2 is the mode of the value comparison of luminance difference of the present invention.
Fig. 3 is the mapping functional arrangement of one embodiment of the invention.
Fig. 4 is original transfer function figure of the present invention.
Fig. 5 is a bidimensional image brightness value.
Fig. 6 is image pixel spot scan mode schematic diagram among the present invention.
Fig. 7 is the schematic diagram of the positive force sequence and the negative force sequence of embodiments of the invention.
Fig. 8 is the clean positive force sequence schematic diagram according to Fig. 5 gained.
Fig. 9 is the clean negative force sequence schematic diagram according to Fig. 5 gained.
Figure 10 is the clean power sequence schematic diagram that Fig. 8,9 is synthesized.
Figure 11 is for adjusting Figure 10 according to Fig. 3 the new power sequence schematic diagram of back gained.
Figure 12 is Figure 11 integral result schematic diagram.
Figure 13 is the expansionary force function schematic diagram of gained after Figure 12 normalization.
Figure 14 be after Fig. 4 and Figure 13 linear combination brightness transition function schematic diagram.
Figure 15 is another embodiment of the present invention form one power sequence schematic diagram.
Figure 16 is another embodiment of the present invention form two power sequence schematic diagrames.
Figure 17 is the flow chart of Figure 15 of the present invention and Figure 16.
Embodiment
In view of prior art when improving image contrast, still can produce some problems, calculation of complex may occur, cause noise to amplify or image shortcoming such as nature, therefore, the present invention proposes a kind of image contrast and adds strong method, to improve above-mentioned disappearance.
Figure 1 shows that image contrast of the present invention adds the flow chart of steps of strong method, at first at step S10, one image is provided, then calculate the value of adjacent two pixel luminance differences at step S12, account form as shown in Figure 2, wherein English alphabet A～I is the brightness value information of pixel, for pixel brightness value E, in the present invention, calculate the luminance difference value information of this value and contiguous eight pixel brightness values on every side, but aforesaid way may cause the double counting phenomenon, therefore in fact only need to calculate monochrome information E and monochrome information A, B, the brightness value difference between C and the D gets final product, shown in Fig. 2 solid line, carry out step S14 again, whether the value of judging luminance difference is greater than a default threshold value, and this threshold value generally is made as three times of values of noise criteria difference in the image, but also can be selected voluntarily by the user.If the value of luminance difference is greater than preset threshold value, then carry out step S16, produce corresponding positive force sequence according to brightness value, and this power sequence and the positive force sequence that last time produced are done one add up, if the luminance difference value is less than preset threshold value, then carry out step S18, produce corresponding negative force sequence according to brightness value, and this power sequence and the negative force sequence that last time produced are done one add up, each positive force sequence and its power size of negative force sequence that is produced is 1, the positive force sequence of S16 and S18 and the generation of negative force sequence and accumulating operation will repeat running always, till checking all pixel information of importing image, as step S20.Then carry out step S22, clean positive force sequence is deducted the clean negative force sequence that adds weight, become a clean power sequence, when if its value of the arbitrary clean power in this clean power sequence is negative, then should value further be set at zero, after finishing step S22, carry out step S24 again, the clean power sequence of integration, and with integrated value normalization at 0 to 255, to obtain an expansionary force function,, expansionary force function and original brightness transfer function are carried out linear combination at last at step S26, and at step S28, obtain a new brightness transition function, and adjust the brightness value of raw video, to obtain contrasting the image of reinforcement with this function.
Wherein, finish step S22, clean positive force sequence is added that clean negative force sequence becomes clean power sequence after, can utilize the mapping functional value M of kenel as shown in Figure 3
oThe size of clean power sequence is done an adjustment, to obtain a new power sequence.This new power sequence=clean power sequence
(1/Mo), mapping functional value M
oValue for approximately between 1 to 5, right this mapping functional value M
oAlso can set up on their own according to the degree of the required adjustment of image; And brightness transition function=k * expansionary force function+(1-k) * and the original conversion function, k is a binding constant, it is between 0 and 1, and original conversion function kenel is shown in Figure 4.
Below, in order to illustrate characteristics of the present invention better, so enumerate a plurality of embodiment with explanation.
An image at first is provided, as shown in Figure 5, each pixel brightness value in each digitized representation image wherein, then according to shown in Figure 6, in regular turn image pixel is done scanning, when being scanned up to a certain pixel, then according to the luminance difference value between calculating neighbor shown in Figure 2, if the luminance difference value greater than preset threshold value, then produces corresponding positive force sequence according to brightness value, if not, produce corresponding negative force sequence according to brightness value equally, as shown in Figure 7, when the one side scanning element, when on the one hand producing corresponding positive force sequence and negative force sequence, the computing that also each positive force sequence that produces and negative force sequence is added up simultaneously.Image with Fig. 6, each positive force sequence that produces and negative force sequence are added up the clean positive force sequence of back gained and clean negative force sequence shown in Fig. 8,9, clean positive force sequence is deducted the clean negative force sequence that adds weight can obtain clean power sequence, as Figure 10.Then use the mapping function of Fig. 3, wherein M
o=2 with clean power sequence size do one adjust after, can obtain the new power sequence of Figure 11, then new power sequence is carried out integration, can obtain the result of Figure 12, follow again integrated value normalization at 0 to 255, to obtain the expansionary force function of Figure 13.The original transfer function of Fig. 4 and Figure 13 expansionary force function are carried out linear combination, obtain the brightness transition function, as shown in figure 14, and image brilliance is adjusted, adjust the preferable image of back contrast to obtain one with this brightness transition function.
In order to be beneficial to realization on the hardware and the consideration on the cost, the present invention has further proposed two kinds of possible modes the effect of negative force sequence has been incorporated in the positive force sequence, save by this and store the required cost of negative force sequence, Figure 15 is the mode of carrying, according to the original practice, it will produce the positive force sequence between 10 to 50, but in carrying mode one, the form one power sequence that is produced, near the brightness value the flat region, just 10,11 and 50, do not produce corresponding power sequence, avoid the flat region noise to strengthen the problem that computing is exaggerated by this, in order to reach better effect, in Figure 16 institute extracting method two because of contrast, the form two power sequences that produced, except 10,11 and 50 do not produce outside the power sequence, further 11,49 have produced the opposite force sequence, reach better noise suppression effect by this.
According to form one power sequence of being carried and form two power sequences, the entire process flow process can be reduced to Figure 17.At first at step S30, one image is provided, then calculate the value of adjacent two pixel luminance differences at step S32, account form as shown in Figure 2, carry out step S34 again, whether judge the luminance difference value greater than a default threshold value, this threshold value generally is made as the value of three times of noise criteria differences in the image, but also can need and adjustment voluntarily according to the user.If the luminance difference value is greater than preset threshold value, then carry out step S36, produce the form one power sequence or the power sequence of form two according to brightness value, and this power sequence and the power sequence that last time produced are carried out the accumulating operation of S38, the generation of the power sequence of step S36 and S38 and accumulating operation will repeat running always, till last pixel information of input image, as step S40, then carry out step 42, the clean power sequence of integration, and with integrated value normalization at 0 to 255, to obtain an expansionary force function, at last at step S44, expansionary force function and original brightness function are done linear combination, and, obtain a brightness transition function at step S46, and adjust the brightness value of raw video with this function, to obtain contrasting the image of reinforcement.
Image contrast of the present invention adds strong method and also can be applicable on the chromatic image, when a chromatic image is provided, can earlier original RGB chromatic image be converted to other image format, for example HSI or YCbCr, make image be decomposed into a brightness composition image and two color composition images, after we improve brightness composition image, again itself and two color composition images are combined into an image, just can improve contrast, and can not cause the distortion of color.
The present invention proposes a kind of image contrast and adds strong method, the luminance difference value of utilizing image flat region and corner areas is to reach the reinforcement of image contrast, when being corner areas, then produce unidirectional positive force sequence, when being flat site, then produce the power sequence of negative sense, so that being subtracted each other, the two obtains clean power sequence, this method can prevent the shortcoming that the noise of image flat region is reinforced in the lump when contrast is strengthened, in addition, the present invention also can utilize a mapping functional value to obtain a new power sequence to adjust clean power sequence, strengthen the not nature that the back is produced to avoid image in contrast, the function of this function is exactly the expansionary force that keeps excessive, strengthens less expansionary force, to reach the purpose that the image naturality is preserved.
In addition, in order to lower hardware burden and cost, the present invention has further proposed two kinds of multi-form power sequences (form one and form two), as if the basis of strengthening as a comparison with this power sequence, can further save and calculate the required cost of negative force sequence.
The above is by embodiment characteristics of the present invention to be described, its purpose makes those skilled in the art can better understand content of the present invention and is implementing according to this, rather than in order to limit the present invention, for those of ordinary skill in the art under the prerequisite that does not break away from spirit of the present invention and category, any equivalent modifications or change to the present invention carries out all should be included in the claim of the present invention.
Claims (12)
1. an image contrast adds strong method, and its step comprises:
A., one image is provided, and calculates the value of the luminance difference of adjacent two pixels, and this image has an original brightness function;
Whether the value of b. judging described luminance difference is greater than a default threshold value;
If b1., then produce a positive force sequence;
B2. if not, then produce a negative force sequence;
Repeating step b is till all pixels that check out described image;
C. the described positive force sequence among the step b is added up and obtain a clean positive force sequence, and described negative force sequence added up obtain a clean negative force sequence, then, described clean positive force sequence is deducted add weight described clean negative force sequence to obtain a clean power sequence;
D. this clean power sequence is carried out integration, and carry out in 0 to 255 of normalization, to obtain an expansionary force function; And
E. with this expansionary force function and this original brightness function linear combination, to obtain a brightness transition function, adjust the brightness value of this image, and then strengthen this image contrast with this brightness transition function.
2. image contrast as claimed in claim 1 adds strong method, and wherein, in step b, this threshold value differs from 3 times value for the noise criteria in this image.
3. image contrast as claimed in claim 1 adds strong method, wherein, behind step c, utilizes a mapping functional value M
oAdjust this clean power sequence, to obtain a new power sequence, new power sequence=clean power sequence
(1/Mo), and then carry out steps d.
4. image contrast as claimed in claim 3 adds strong method, wherein, and this mapping functional value M
oValue be 1≤M
o≤ 5.
5. image contrast as claimed in claim 1 adds strong method, wherein, and this brightness transition function=k * this expansionary force function+(1-k) * this original brightness function, this k is a binding constant, and its value is between 0 and 1.
6. an image contrast adds strong method, and its step comprises:
A., one image is provided, and calculates the value of the luminance difference of adjacent two pixels, and this image has an original brightness function;
Whether the value of b. judging described luminance difference is greater than a default threshold value;
If b1., then produce a power sequence;
B2. if not, then judge the value of next luminance difference, finish until judgement;
C. described power sequence is carried out adding up, to obtain a clean power sequence;
D. this clean power sequence is carried out integration, and carry out in 0 to 255 of normalization, to obtain an expansionary force function; And
E. with this expansionary force function and this original brightness function linear combination, to obtain a brightness transition function, adjust the brightness value of this image, and then strengthen the contrast of this image with this brightness transition function.
7. image contrast as claimed in claim 6 adds strong method, and wherein, in step b, this threshold value differs from 3 times value for the noise criteria in this image.
8. image contrast as claimed in claim 6 adds strong method, wherein, after the addition of described power sequence becomes the step c of this clean power sequence, utilizes a mapping functional value M
oAdjust this clean power sequence, to obtain a new power sequence, new power sequence=clean power sequence
(1/Mo), and then carry out steps d.
9. image contrast as claimed in claim 8 adds strong method, wherein, and this mapping functional value M
oValue be 1≤M
o≤ 5.
10. image contrast as claimed in claim 6 adds strong method, wherein, and this brightness transition function=k * this expansionary force function+(1-k) * this original brightness function, this k is a binding constant, and its value is between 0 and 1.
11. the described image contrast of claim 6 adds strong method, wherein, in step b1, the value of each described luminance difference is between between a fractional value and a big numerical value, add 2 at each this fractional value and subtract 1 power sequence that produces the value of corresponding each this luminance difference to this greatest measure, and the addition of described power sequence is become this clean power sequence.
12. image contrast as claimed in claim 6 adds strong method, wherein, in step b1, the value of each described luminance difference is between between a fractional value and a big numerical value, add 2 at this fractional value and subtract 1 positive force sequence that produces the value of corresponding each this luminance difference to this big numerical value, and this fractional value add 1 and this greatest measure subtract 1 place and respectively obtain an opposite force sequence, described positive force sequence and described opposite force sequence are synthesized a power sequence, and the addition of described power sequence are become this clean power sequence.
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| TWI338514B (en) | 2006-01-20 | 2011-03-01 | Au Optronics Corp | Image processing method for enhancing contrast |
| CN100388757C (en) * | 2006-02-13 | 2008-05-14 | 友达光电股份有限公司 | Method of improving image contrast |
| CN101577832B (en) * | 2008-05-06 | 2012-03-21 | 联咏科技股份有限公司 | Image processing circuit and image processing method for strengthening character display effect |
| CN103137098B (en) * | 2011-12-02 | 2015-06-17 | 联咏科技股份有限公司 | Tone corresponding method |
| CN104539935B (en) | 2015-01-19 | 2017-05-31 | 北京京东方多媒体科技有限公司 | The adjusting method and adjusting means of brightness of image, display device |
Citations (5)
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|---|---|---|---|---|
| CN1168049A (en) * | 1996-03-09 | 1997-12-17 | 三星电子株式会社 | Image enhancing method using mean-separate histogram equalization and circuit therefor |
| CN1179059A (en) * | 1996-06-20 | 1998-04-15 | 三星电子株式会社 | Image reinforced circuit using reducing noise and histogram equilibrium and its method |
| CN1209705A (en) * | 1997-08-21 | 1999-03-03 | 力捷电脑股份有限公司 | Method and apparatus for forming again picture with poignant contrast in picture system |
| US20020154832A1 (en) * | 2001-03-10 | 2002-10-24 | Sobol Robert E. | Method for contrast mapping of digital images that converges on a solution |
| US20030035579A1 (en) * | 2001-08-18 | 2003-02-20 | Samsung Electronics Co., Ltd. | Apparatus and method for equalizing histogram of an image |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1168049A (en) * | 1996-03-09 | 1997-12-17 | 三星电子株式会社 | Image enhancing method using mean-separate histogram equalization and circuit therefor |
| CN1179059A (en) * | 1996-06-20 | 1998-04-15 | 三星电子株式会社 | Image reinforced circuit using reducing noise and histogram equilibrium and its method |
| CN1209705A (en) * | 1997-08-21 | 1999-03-03 | 力捷电脑股份有限公司 | Method and apparatus for forming again picture with poignant contrast in picture system |
| US20020154832A1 (en) * | 2001-03-10 | 2002-10-24 | Sobol Robert E. | Method for contrast mapping of digital images that converges on a solution |
| US20030035579A1 (en) * | 2001-08-18 | 2003-02-20 | Samsung Electronics Co., Ltd. | Apparatus and method for equalizing histogram of an image |
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