CN105516545A - Automatic contrast enhancement system - Google Patents
Automatic contrast enhancement system Download PDFInfo
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- CN105516545A CN105516545A CN201410522611.2A CN201410522611A CN105516545A CN 105516545 A CN105516545 A CN 105516545A CN 201410522611 A CN201410522611 A CN 201410522611A CN 105516545 A CN105516545 A CN 105516545A
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Abstract
The invention discloses an automatic contrast enhancement system. The automatic contrast enhancement system comprises a local difference histogram unit based on a human visual sense system and used to build a local difference histogram with respect to intensity values; a histogram classifier, which can be used for classification of histograms of input images according to distribution characteristics; and a histogram equalization unit, which is used to process the input images according to the result of the local difference histogram unit based on the human visual sense system and the enhanced level determined by the histogram classifier.
Description
Technical field
The present invention relates to a kind of contrast intensification's system automatically, particularly relate to a kind of automatic contrast intensification's system based on human visual system (HVS) suppressing seondary effect.
Background technology
Image enhancement is often in order to improve the image that low contrast image or imperfect Irradiance capture.Convention control strengthens algorithm and often causes excessive strengthening, makes image seem natural and the noisy amplification of meeting.
Histogram strengthening (HE) is the most frequently used with one of method improving contrast intensification.By histogram strengthening, image intensity can be allowed more to be evenly distributed to reach better contrast.The overall complexity of histogram strengthening algorithm is lower than additive method.But histogram strengthening is easy to produce excessively strengthening, noise amplifies, details is missed or allows image seem nature.
Moreover human eye cannot differentiate the Strength Changes of zone of saturation.Zone of saturation is regarded as usually not containing the smooth region of texture information.In fact, zone of saturation often keeps the colourity (hue) of faint Strength Changes and random distribution.If directly use contrast intensification, zone of saturation can produce strong noise and amplify.
Therefore, suitable strengthening position is accurate is indispensable in contrast intensification's system with seondary effect reduction method.
Summary of the invention
In view of above-mentioned, the object of the invention is to, a kind of contrast intensification's system is automatically provided, technical problem to be solved makes it consider human vision sensitivity to set up histogram, and according to its distribution automatically to determine that the strengthening position relevant to device is accurate, the saturated degeneration produced after contrast intensification can by Saturated strain-hardening to compensate, and image local can be improved saturated and chrominance noise amplification can not be had, moreover the overall complexity of its algorithm is very low, is suitable for hardware implementation and immediately applies.
The object of the invention to solve the technical problems realizes by the following technical solutions.According to the automatic contrast intensification's system of one that the present invention proposes, it comprises changes unit based on partial error's histogram unit of human visual system, histogram classifier and histogram etc.Partial error's histogram unit based on human visual system receives the input pixel of input image, to set up the partial error's histogram relative to intensity level.Histogram classifier is classified according to the histogram of distribution character to input image, thus obtains multiple classification.It is accurate according to the strengthening position that should determine based on result and the histogram classifier of partial error's histogram unit of human visual system that histograms etc. change unit, process input image.
The object of the invention to solve the technical problems also can be applied to the following technical measures to achieve further.
Aforesaid automatic contrast intensification's system, uses the brightness of colourity-saturation-brightness (HSL) color space as this intensity.
Aforesaid automatic contrast intensification's system, wherein this intensity levels all are split into multiple region according to human vision sensitivity.
Aforesaid automatic contrast intensification's system, wherein at this partial error's histogram unit based on human visual system, when the intensity difference between the neighbor of this input image is greater than a preset critical, namely the intensity level of current pixel adds up into this partial error's histogram.
Aforesaid automatic contrast intensification's system, wherein has the preset critical being greater than the region with higher-strength value compared with the preset critical in the region of low intensity value.
Aforesaid automatic contrast intensification's system, histogram wherein one of in the middle of the plurality of classification, the quantity of its intensity values and low intensity value is larger, and the negligible amounts of other intensity levels, wherein, the mean value of intensity values and the mean value of low intensity value distance are between the two larger, then determine to obtain larger strengthening position accurate.
Aforesaid automatic contrast intensification's system, histogram wherein one of in the middle of the plurality of classification, it mainly comprises bright intensity level or dark intensity level, wherein, the mean value of bright intensity more close to the mean value of minimum intensity value or dark intensity more close to highest intensity value, then determine to obtain larger strengthening position accurate.
Aforesaid automatic contrast intensification's system, also comprises seondary effect and reduces unit, in order to reduce the seondary effect because contrast intensification causes.
Aforesaid automatic contrast intensification's system, wherein this seondary effect reduction unit comprises peak detection sub-cell, and in order to the spike of identification smooth region, and the noise reducing this smooth region according to this amplifies.
Aforesaid automatic contrast intensification's system, wherein this seondary effect reduces unit and comprises skin and gradient color detect sub-cell, its detecting skin or gradient color region, and suppresses according to this to strengthen position standard, thus avoids unexpected or factitious skin/gradient color.
Aforesaid automatic contrast intensification's system, wherein this seondary effect reduces unit and comprises overexposure and prevent sub-cell, overexposure is eliminated in high intensity region, wherein, according to the distribution of content of the high strength of this input image, adapt to ground and determine high strength critical value, if intensity level is less than this critical value, then impose the changes such as histogram; Otherwise, directly map to output intensity from input intensity.
The present invention compared with prior art has obvious advantage and beneficial effect.By technique scheme, the present invention automatic contrast intensification system at least has following advantages and beneficial effect: automatic contrast intensification's system of the present invention considers human vision sensitivity to set up histogram, according to its distribution automatically to determine that the strengthening position relevant to device is accurate, the saturated degeneration produced after contrast intensification can by Saturated strain-hardening to compensate, and image local can be improved saturated and chrominance noise amplification can not be had, moreover, the overall complexity of its algorithm is very low, is suitable for hardware implementation and immediately applies.
In sum, the invention relates to a kind of contrast intensification's system automatically, it comprises: based on partial error's histogram unit of human visual system, in order to set up the partial error's histogram relative to intensity level; Histogram classifier, classifies according to the histogram of distribution character to input image; And histogram etc. changes unit, accurate according to the strengthening position that this result based on partial error's histogram unit of human visual system and histogram classifier determine, process inputs image.The present invention has significant progress technically, and has obvious good effect, is really a new and innovative, progressive, practical new design.
Above-mentioned explanation is only the general introduction of technical solution of the present invention, in order to technological means of the present invention can be better understood, and can be implemented according to the content of specification, and can become apparent to allow above and other object of the present invention, feature and advantage, below especially exemplified by preferred embodiment, and coordinate accompanying drawing, be described in detail as follows.
Accompanying drawing explanation
Fig. 1 is the block diagram of automatic contrast intensification's system of the display embodiment of the present invention.
Fig. 2 A is the schematic diagram of display according to the cutting of the intensity gradient of human vision sensitivity.
Fig. 2 B to Fig. 2 E is that the partial error's histogram unit based on human visual system of display Fig. 1 manages the histogram in stage throughout.
Fig. 3 A to Fig. 3 E illustrates the histogram that the histogram classifier being subject to Fig. 1 carries out classifying.
Fig. 4 illustrates histogram has noise amplification schematic diagram at smooth region.
Fig. 5 is the schematic diagram of the mapping curve illustrating overexposure region.
Fig. 6 A is the schematic diagram of display colorimetric plane.
Fig. 6 B is the border circular areas of the colorimetric plane of display Fig. 6 A, in order to the schematic diagram of separate color region and low zone of saturation.
100: contrast intensification's system automatically
11: based on partial error's histogram unit of human visual system
12: histogram classifier
13: histogram eqalizing cricuit
14: seondary effect reduces unit
141: peak detection sub-cell
142: skin and gradient color detect sub-cell
143: dark zone of saturation preliminary treatment sub-cell
144: overexposure prevents sub-cell
DS: dark zone of saturation
SV: slow region of variation
FV: fast region of variation
BS: bright zone of saturation
Embodiment
For further setting forth the present invention for the technological means reaching predetermined goal of the invention and take and effect, below in conjunction with accompanying drawing and preferred embodiment, to automatic its embodiment of contrast intensification's system proposed according to the present invention, structure, feature and effect thereof, be described in detail as follows.
Fig. 1 is the block diagram of automatic contrast intensification's system 100 of the display embodiment of the present invention.The execution of automatic contrast intensification's system 100 can make purpose processor (such as digitized video processor), circuit or its combination.
Automatic contrast intensification's system 100 comprises partial error (localdifference, the LD) histogram unit 11 based on human visual system (HVS), and it receives the input pixel of input image.According to one of feature of the present embodiment, use the brightness of colourity-saturation-brightness (HSL) color space as intensity, but not as traditional consolidation system colourity-saturation-lightness (HSV) color space of using.Because intensity respectively has different qualities, all intensity levels (such as 0 to 255) are cut into multiple (such as four) region according to human vision sensitivity by the present embodiment: secretly saturated (DS) region, gradualization (SV) region, fast change (FV) region and bright saturated (BS) region, as shown in Figure 2 A.
Partial error's histogram unit 11 based on human visual system is the different qualities of the contrast sensitivity considering each region, sets up partial error's histogram, in order to carry out suitable adjustment to different shape content.Intensity difference between neighbor is greater than preset critical, and namely the intensity of current pixel add up into partial error's histogram.It should be noted that the critical value in each region can be difference.In general, there is the critical value being greater than the region with higher-strength value compared with the critical value in the region of low intensity value.
Fig. 2 B illustrates former histogram, after it is subject to the process based on partial error's histogram unit 11 of human visual system, produces partial error's histogram as that shown in fig. 2 c.It should be noted that produced partial error's histogram (Fig. 2 C) can be difference for the amount of suppression of zones of different.In general, there is the suppression suffered by the peak value being greater than the region with higher-strength value compared with the suppression suffered by the peak value in the region of low intensity value.Then, partial error's histogram (Fig. 2 C) combines with even (uniform) histogram (Fig. 2 D) and improves histogram to be formed, as shown in Figure 2 E.
Refer to shown in Fig. 1, automatic contrast intensification's system 100 also comprises histogram classifier 12, and it is classified according to the histogram of distribution character by multiple input image.For each classification, determine that different strengthening positions is accurate respectively.In one embodiment, three classifications are at least obtained.For the histogram of the first category illustrated in Fig. 3 A or Fig. 3 B, the quantity of intensity values and low intensity value is comparatively large, and the negligible amounts of other intensity levels.In general, the mean value of intensity values and the mean value of low intensity value distance are between the two larger, then determine to obtain larger strengthening position accurate.For other histogram of Equations of The Second Kind illustrated in Fig. 3 C or Fig. 3 D, mainly comprise bright intensity (Fig. 3 C) or dark intensity (Fig. 3 D).In general, the mean value of bright intensity more close to the mean value of minimum intensity value or dark intensity more close to highest intensity value, then determine to obtain larger strengthening position accurate.Differ from first category and other histogram of Equations of The Second Kind (such as Fig. 3 E) is then classified as the 3rd classification in the present embodiment.The image belonging to the 3rd classification does not need to strengthen.
Then, according to based on partial error's histogram unit 11 of human visual system and the result (such as, the mapping curve of constrained input intensity) of histogram classifier 12, use histogram eqalizing cricuit (HE) 13 to process input image.Histogram eqalizing cricuit 13 can use the change technology such as traditional histogram to implement, and its details is omitted at this.
According to another feature of the present embodiment, automatic contrast intensification's system 100 comprises seondary effect and reduces unit 14, and in order to reduce seondary effect, the excessive strengthening such as caused because of contrast intensification or noise amplify.The seondary effect reduction unit 14 of the present embodiment comprises spike (spike) and detects sub-cell 141, and in order to the spike of identification smooth region, and the noise reducing smooth region according to this amplifies.Fig. 4 illustrates histogram and has noise amplification at smooth region.According to the result of peak detection sub-cell 141, according to number of pixels and the spike distribution of spike, it is accurate that dynamic reduces strengthening position.
The seondary effect reduction unit 14 of the present embodiment also comprises skin and gradient color detects sub-cell 142, its detecting skin or gradient color region, and suppresses strengthening position accurate according to this, thus avoids unexpected or factitious skin/gradient color.
The seondary effect of the present embodiment reduces unit 14 and also comprises dark zone of saturation preliminary treatment sub-cell 143, uses partial smoothing technology to remove noise and color change.In this manual, zone of saturation is defined as to have high or pole hypo-intense pixels, and human eye cannot differentiate the region of its Strength Changes easily.Zone of saturation must careful selection and do not eliminate useful information.
The seondary effect reduction unit 14 of the present embodiment also comprises overexposure and prevents sub-cell 144, eliminates overexposure in high intensity region.Fig. 5 illustrates the mapping curve in overexposure region.In order to deal with this situation, according to the distribution of content of high strength, adapting to ground and determining high strength critical value.If intensity is less than this critical value, then impose the changes such as histogram; Otherwise, directly map to output intensity from input intensity.
According to the another feature of the present embodiment, after contrast intensification, also perform Saturated strain-hardening, when the pixel intensity of colourity-saturation-brightness (HSL) color space changes, in order to compensate the saturated decline of produced vision.Fig. 6 A shows colorimetric plane.Not visible chrominance information is positioned at hypo-intense region (A), low zone of saturation (B) and high intensity region (C).If directly perform Saturated strain-hardening in these regions, then chrominance information can be amplified.Amplify to increase image saturation but not there is noise colourity, need to differentiate color and greyscale pixel.Saturated strain-hardening only imposes on appropriate area and amplifies to avoid noise colourity.In order to reduce computation complexity, imposing Saturated strain-hardening based on distance in the border circular areas shown in Fig. 6 B, can computation complexity be reduced.According to from saturated with brightness position the distance to maximum saturation point, calculate Saturated strain-hardening position according to this accurate.
The above, it is only preferred embodiment of the present invention, not any pro forma restriction is done to the present invention, although the present invention discloses as above with preferred embodiment, but and be not used to limit the present invention, any those skilled in the art, do not departing within the scope of technical solution of the present invention, make a little change when the technology contents of above-mentioned announcement can be utilized or be modified to the Equivalent embodiments of equivalent variations, in every case be do not depart from technical solution of the present invention content, according to any simple modification that technical spirit of the present invention is done above embodiment, equivalent variations and modification, all still belong in the scope of technical solution of the present invention.
Claims (11)
1. automatic contrast intensification's system, is characterized in that it comprises:
Based on partial error's histogram unit of human visual system, receive the input pixel of input image, to set up the partial error's histogram relative to intensity level;
Histogram classifier, classifies according to the histogram of distribution character to input image, thus obtains multiple classification; And
Histograms etc. change unit, accurate according to the strengthening position that this result based on partial error's histogram unit of human visual system and this histogram classifier determine, process this input image.
2. automatic contrast intensification's system according to claim 1, is characterized in that it uses the brightness in colourity-saturation-brightness and color space as this intensity.
3. automatic contrast intensification's system according to claim 1, is characterized in that wherein this intensity levels all are split into multiple region according to human vision sensitivity.
4. automatic contrast intensification's system according to claim 3, it is characterized in that wherein at this partial error's histogram unit based on human visual system, when intensity difference between the neighbor of this input image is greater than a preset critical, namely the intensity level of current pixel adds up into this partial error's histogram.
5. automatic contrast intensification's system according to claim 4, is characterized in that wherein having the preset critical being greater than the region with higher-strength value compared with the preset critical in the region of low intensity value.
6. automatic contrast intensification's system according to claim 1, the histogram one of to it is characterized in that in the middle of wherein the plurality of classification, the quantity of its intensity values and low intensity value is larger, and the negligible amounts of other intensity levels, wherein, the mean value of intensity values and the mean value of low intensity value distance are between the two larger, then determine to obtain larger strengthening position accurate.
7. automatic contrast intensification's system according to claim 1, the histogram one of to it is characterized in that in the middle of wherein the plurality of classification, it mainly comprises bright intensity level or dark intensity level, wherein, the mean value of bright intensity more close to the mean value of minimum intensity value or dark intensity more close to highest intensity value, then determine to obtain larger strengthening position accurate.
8. automatic contrast intensification's system according to claim 1, is characterized in that it also comprises seondary effect and reduces unit, in order to reduce the seondary effect because contrast intensification causes.
9. automatic contrast intensification's system according to claim 8, it is characterized in that wherein this seondary effect reduces unit and comprise peak detection sub-cell, in order to the spike of identification smooth region, and the noise reducing this smooth region according to this amplifies.
10. automatic contrast intensification's system according to claim 8, it is characterized in that wherein this seondary effect reduces unit and comprise skin and gradient color detects sub-cell, its detecting skin or gradient color region, and suppress strengthening position accurate according to this, thus avoid unexpected or factitious skin/gradient color.
11. automatic contrast intensification's systems according to claim 8, it is characterized in that wherein this seondary effect reduction unit comprises overexposure and prevent sub-cell, overexposure is eliminated in high intensity region, wherein, according to the distribution of content of the high strength of this input image, adapt to ground and determine high strength critical value, if intensity level is less than this critical value, then impose the changes such as histogram; Otherwise, directly map to output intensity from input intensity.
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Application publication date: 20160420 |