System and method for correcting dark tones on digital photographs

FIELD: digital processing of images, possible use for global and local correction of brightness of digital photographs.

SUBSTANCE: system and method for correcting dark tones in digital photographs contain global contrasting module, module for conversion from RGB color system, module for determining dark tone amplification coefficient, bilateral filtration module, dark tone correction module, module for conversion to RGB color system, random-access memory block, displaying device. Global contrasting module is made with possible correction of global image contrast, module for conversion from RGB color system is made with possible conversion of image from RGB color system to three-component color system, one component of which is image brightness, and two others encode color, module for conversion to RGB color system is made with possible conversion from three-component color system, one of components of which is image brightness, and two others encode color, back to RGB color system, module for determining dark tone amplification coefficient is made with possible computation of global image brightness bar graph and can determine dark tone amplification coefficient based on analysis of signs, calculated from global image brightness bar graph, bilateral filtration module is made with possible execution of bilateral filtration of image brightness channel, dark tone correction module is made with possible correction of dark tones in image brightness channel.

EFFECT: absence of halo-effect.

2 cl, 17 dwg

 

The invention relates to the field of digital image processing, and more specifically to techniques for global and local brightness correction of digital photos.

In this region there is an acute problem of correcting color casts in images with low dynamic range in dark shades, the cause of which may be, for example, the backlight lighting or shooting with flash in a dark room.

There are several research directions for improving local contrast color photographs, including correction of dark shades.

Intuitive and relatively simple method of local corrections of dark and light shades are described in U.S. patent No. 6822762 [1]. The amount of compensation depends on the value of the mask, which is created in the blur of the luminance channel of an image of a linear low-pass filter.

A similar approach is described in U.S. patent No. 6792160 [2]. Similar technology is used in a number of programs for image adjustment, for example, in the menu item "Shadow/Highlight" Adobe Photoshop CS [3].

The main drawback of these approaches is the emergence of the image of the so-called "halo effect" - a halo along the sharp changes in brightness.

A slightly different approach is described in another series of patent filings and the U.S. (U.S. patent No. 6760484 [4], tiled application U.S. No. 2002/0154323 [5], 2002/0154832 [6], 2003/0161546 [7], 2004/0174571 [8]), which offer a way to the correction of shadows, based on the modification of the algorithm MultiScale Retinex (MSR). Briefly the essence of the approach is the following. Modified MSR is performed for the luminance channel, which is calculated as the maximum of the intensities of the channels R, G, B. the Classic MSR is described by the formula:

where LPF - Gaussian blur with different dispersions σ2.

In the approach [4]-[8] for the Gaussian blur used Express computational scheme, to which is added a number of threshold values. The described method is used in HP "Adaptive Lighting".

In the international application WO 02/089060 [9] describes a method of enhancing images based on Orthogonal Retino-Morphic Image Transform (ORMIT):

where Pi(x) - orthogonal basis functions of X, defined in the range 0<x<1, Qi(x) is defined analytically or by using the approximation of the integral of Pi(x), LPF - operator low-pass filter, F is a weight function, N is the number of sub - bands, which splits the entire available range of brightness, a and b are constants, in General, different for each subband. Selection of the appropriate functions of Pi(x) allows to increase local contrast and the signal level in dark shades. The described method is used in the technology of the Nikon "D-Lighting".

In article Brajovic, V., "Brightness Perception, Dynamic Range and Noise: a Unfied Model for Adaptive Image Sensors", Proceedings of the 2004 IEEE Computer Society Conference on Computer Vision and Pattern Recognition, vol.: 2, pp.II-189-II-196 [10] described a method of reproducing images with a high dynamic range of brightness on devices that can reproduce a smaller range of brightness. This method is described for grayscale (black and white) and includes the correction of dark shades:

I=S(R+aL),

where a and S are constants, L is the result of filtering (in this case, blur) with protection boundaries with high local contrast, R - relation function of the initial luminance to L. the Filtering is performed for each row of the image. The filter parameters based on the assessment of the level of noise in the image.

Methods do not evaluate adaptive necessity and degree of correction. In tiled application U.S. No. 2004/0120599 [11] described a variant of evaluating the presence of backlight on the image. When this image with the backlight light detected by analyzing the luminance histograms to determine whether the histogram the form of an inverted bell or double peak, by smoothing the histogram approximation of the smoothed histogram curve, counting the number of intersections of the curve with the x-axis, attributing the image to the category of the "backlight", if the number of intersections is greater than or equal to four.

Despite the large number of known solutions, all of them who have significant drawbacks:

a number of methods describes a correction method only for grayscale (black and white) images and does not describe for color;

- the existing methods do not address the relationship of the correction darker with the setting of the global contrast of the image;

- the use of algorithms based on the local nonlinear masking causes halo (halo effect) along the sharp changes in brightness in the image. When using algorithms based on MSR or ORMIT, halo-effect is less pronounced and occurs only for a specific type of image, but also has a place;

- use any of the existing algorithms leads to an increase of the noise level in the area of the dark shades;

existing solutions are not adaptive, the degree (strength) of the correction is not determined automatically. If you be subjected to the correction of the image quality, its quality will deteriorate. Often there is reduction in the dynamic range of tones in the midtones.

Closest to the claimed solution is the approach described in the paper [10], which is selected as a prototype of the invention.

The problem to which the invention is directed, is to develop a system and method for correcting dark shades (shadow) and global contrast mainly color digital photos, which is e cause a halo effect.

The technical result is achieved by establishing a system for the correction of dark shades on the image that contains the module global contrast, the conversion module from the color system RGB module determining gain dark shades, module bilateral filtering module, the correction of dark shades, the module converting the color system RGB memory, which stores the original image, the display device, which displays the result of the correction, and output module global contrast enhancement is associated with the input module to convert the color system RGB output for transmission of the brightness channel of the module converting from RGB coloring connected with the inputs of the module determining the gain dark shades, module, bilateral filtering and correction module darker, and the output for transmission of the color channels of the module converting from RGB coloring connected with the input module converting the color system RGB output module determining gain dark shades associated with the input module, the correction of dark shades, the output module bilateral filter is connected to the input module, the correction of dark shades, the module output correction darker connected with the input module conversion in the color systems is RGB, the output module converting the color system RGB is connected to the input of a display device, the module global contrast is made with the possibility of correction of the global contrast of the image extension conversion from the color of the RGB system is arranged to convert the image from color system RGB three-color system, one component of which is the brightness of the image, and the other two encode the color module converting the color system RGB is made with the possibility of conversion of the three-color system, one component of which is the brightness of the image, and the other two encode color, back color system RGB module determining the gain of the dark shades made with the possibility to calculate the global histogram of the brightness of the image and to determine the gain in dark colors on the basis of the analysis of the characteristics calculated from the global histogram of the brightness of the image, the module bilateral filtering is executed with the ability to perform bilateral filtering of the luminance channel of the image, the correction module dark shades made with the possibility to adjust the dark shades in the luminance channel of the image.

The system makes sense that the display device was the imp is prevalent in the form of a printer or similar in function to the print device, or in the form of a monitor or similar device functions.

The technical result is also achieved by creating a method for correcting dark shades on digital photographs, comprising the following steps:

- carry out the correction of the global contrast in the global contrast of the image and transmit the result to the module conversion from the color system RGB

- module conversion of the color system RGB convert the image from color system RGB three-color system, one component of which is the brightness of the image, and the other two encode color, and transmits the luminance channel in the module definition gain dark shades, module bilateral filtering module correction of dark shades, and the color channels are passed to the module converting the color system RGB

determine module for determining the coefficient of dark shades gain dark shades by analyzing the characteristics calculated from the global histogram of brightness, and transmit this coefficient in the correction module darker

- conduct bilateral filtering of the luminance channel in the module bilateral filtering and transmit the result to the correction module darker

- compute module correction dark shades of the image in the detail, which is a function of the relationship of the image and brightness of the bilateral filter,

- adjust module correction dark shades dark shades in the luminance channel by adding to the lightness channel works the difference between image detail and brightness on the inversion of brightness and a gain of dark shades, the result is the adjusted brightness values that are passed into the module converting the color system RGB

- convert image color system RGB module converting the color system RGB and transmit the result to the display device.

In the process it is important that the image from the color system is converted into RGB three-color system HSV (hue, saturation, brightness).

In the process it is essential that hold bilateral filtering of the luminance channel using superanalogue bilateral filter in which the filtering is carried out first by row and then column of the image.

In the process it is essential that hold bilateral filtering of the luminance channel using superanalogue bilateral filter, which uses the Gaussian function with standard deviations in space σD=5 and gradation Yar is barb σ R=0,1(2n-1), where n is the color depth per channel.

In the process it is essential that determines the gain of the dark shades by analyzing characteristics:

share shades in the shadows

- the share of the shades in the first half shadow

- the share of the shades in the second half shadow

share shades of grayscale,

share shades of bright colours,

- the ratio of the maximum of the histogram in the shadows to the global maximum of the histogram,

- the ratio of the maximum of the histogram in the midtones to the global maximum of the histogram,

- the ratio of the maximum of the histogram in bright colours to the global maximum of the histogram,

- the position of the maximum of the histogram in the shadows

- the position of the maximum of the histogram in bright colors.

In the process it is essential that calculates the image details, while using the ratio:

D=f(Vf,V)=(2n-1)kV/(Vf+b)

where D is the brightness of the intermediate image parts, V - the brightness of the original image, Vf- the brightness of the image in the bilateral filtering brightness, b=3σRthat σR- setting bilateral filter, constant k=1,2, n - color depth per channel.

In the process substantially correct dark shades in the luminance channel, while using the ratio:

V=fw(V+a(2n-1-V)fb(-V)),

,

where D is the brightness of the intermediate image parts, V - the brightness of the original image, and a gain of dark shades, the n - color depth per channel.

In the process it is important that calculates the image details and correct dark shades, while pre-compute two-dimensional conversion table in which retain the adjusted brightness depending on the brightness before the correction, reflected in the line number table and the bilateral filter, which is reflected in the number of the table column.

For a better understanding of the present invention further provides a detailed description involving graphic materials.

Figure 1. Component diagram of the system according to the invention.

Figure 2. The block diagram of steps of correction according to the invention.

Figure 3. The block diagram of the global contrast.

Figure 4. A block diagram of a method of determining the gain in dark colors.

Figure 5. An example of a properly exposed pictures 5(a) and pictures with backlight illumination 5(C) and their histograms of brightness 5(b) and 5(d), respectively.

6. A table with characteristic values and gain dark shades for photos 5(a) and 5(C).

7. An example of image correction, where (6A) is the original image is reflected, 6(b) is the result of the correction, 6(C) is the result of bilateral filtering the luminance component of the image, 6(d) image details.

Fig. The comparison results of the proposed method of correction for the original image 7(b) of the inventive method 7(C) and method used in the commercial Adobe Photoshop CS menu Shadow/Highlight 7(a).

Consider the basic ideas underlying the method for correcting dark shades in this invention on the example of grayscale images with brightness in the range from 0 to 1.

A number of photographs, for example, damaged against strong back light, have a low dynamic range of shades in dark areas. For the observer this leads to the fact that the details in dark shades of subtle and are darker than the well-exposed photos. Therefore, to improve these photos need to increase local contrast and brightness in dark shades. Suppose we have an image parts D with high local contrast, which is a grayscale image, the details of which are well distinguishable. Then to increase local contrast and increase the signal level in dark shades of the original grayscale image I can use the following alpha blending and I D:

where α - alpha in the sense of prozracnost the matter close to 1 in bright colours and close to 0 in dark colours; the coefficient k regulates the strengthening of local contrast in dark colors. This ratio mixes of the original grayscale image with part of the image details. Removing brackets, you can record this value in a different form:

People recognize details in the image because the brightness is different from the brightness of the background in some of the local area. This statement is similar to the simplest physical model of the formation of a grayscale image I:

where L is the luminance (luminance) of the object varies relatively smoothly, R - reflectivity (reflectance) of objects varies with high frequency (see Horn, B.K.P. "Robot vision", MIT Press, 1986 [12]).

Usually the local background (or illuminance of the object scene L) estimated by blurring the image with a linear low-pass filter, such as Gaussian blur. However, this is not correct from a physical point of view, because in addition to elaborazioni boundaries of objects are blurred and high-contrast edges between objects, which gives a smooth change in L when moving from object to object with different illumination. The ideal solution for obtaining L is the segmentation of the image into regions with the same lighting, but this task today is Yan is intractable. Compromise is the use of blur with the protection of a high-contrast boundaries.

There are several types of filters with protection edge preserving filters). In the literature they are treated as filters for noise suppression. The family of the simplest to implement and effective in terms of time cost filters are bilateral (bilateral) filters (see C.Tomasi, R.Manduchi "Bilateral Filtering for Gray and Color Images", Proc. IEEE conf. on Computer Vision, 1998 [13]):

,

,

for all (r,C) of the pixels of the image, where I is the brightness of the original image, If- brightness in the bilateral filter, r is the row number, the column number, S=3σD- the size of the spatial filter mask, with standard deviations in space, σD- standard deviation space, σR- the standard deviation of gradation of brightness, σDand σRare the filter settings.

In this case, the functions v and w are functions of Gauss, however, it should be noted that the functions v and w may be different than Gaussian (see J.J.Francis, G.de Jager "The Bilateral Median Filter", Proc. of the 14th Annual Symposium of the Pattern Recognition Association of South Africa, 2003 [14]).

The computational complexity of the bilateral filter in the classical the com (see (4)for images of size N×N is O(N2S2), which requires considerable computational costs. Therefore, it is advisable to use a separable bilateral filter in which the filtering is carried out first by row and then by column image:

,

,

where I is the brightness of the original image, Ir- brightness in the bilateral filtering on the rows, If- brightness in the bilateral filter, r is the row number, the column number, S=3σD- the size of the spatial filter mask, with standard deviations in space, σD- standard deviation space, σR- the standard deviation of gradation of brightness.

The computational complexity separable bilateral filter is O(2·N2·S).

According to the above considerations and the formula (3), the image detail is a function of the relationship of the original grayscale image I and the filter bilateral filter If:

As an alpha channel is used, for example, the image itself or the result of bilateral filtering. In PE the PTO if the image is slightly less sharp, but less noisy. In the second case, the image clearer, but the noise level is slightly increased. In this invention it is preferable for the first time.

Thus, the formula (2) is converted to the form:

During implementation, you must consider the color depth of the image being processed and to add to the formula (7) function, which prevents the release within the acceptable range of brightness.

Figure 1 shows a scheme of the interaction of the basic components of the system. In memory 101 stores the original color image of size N×M in the color system RGB color depth d n=d/3 bits per channel. If the image is stored in memory in a color system other than RGB, requires prior conversion to RGB. For correction of the original image in a color system RGB is passed to the module global contrasting 102. Contractorowned the image is transmitted to the module 103 to convert the color system RGB three-color system, one component of which is the brightness of the image, and the other two encode color. Further, the image of the brightness channel is transmitted in definition modules gain dark shades 104, the module bilateral filter 105 and the correction module darker 106. Color the s components are passed to the module converting the color system RGB 107. In the module definition gain dark shades 104 calculates the gain that is passed to the correction module darker 106. In module bilateral filtering is filtering the luminance channel.

In the correction module darker 106 are passed from module to determine the gain dark shades 104 gain dark shades; module converting from RGB coloring 103 image of the luminance channel; module bilateral filter 105 the result of filtering the image of the luminance channel. The image is adjusted luminance channel is passed to the module converting the color system RGB 107. The adjusted image is displayed on the display device 108. The display device may be a printing device, such as a printer or monitor.

Figure 2 shows the block diagram of steps of correction. In step 201 performs the calculation of the global histogram H of brightness of pixels in the image. In step 202 decide on the need for a global contrast enhancement. If the two minimum values of brightness or two maximum brightness values equal to 0 (N[0]==0 and H[1]==0) or (H[2n-3]==0 and N[2n-2]==0)then perform global contrast of the image (step 203). The block diagram of the global contrast is shown in figure 3. In the process the global contrast histogram H is calculated anew.

In step 204, the image from the color system is converted into RGB three-color system, one component of which is the brightness of the image. Most preferred in this invention is a color system HSV (hue, saturation, brightness). To convert use the algorithm described in J.D.Foley, A.van Dam, S.K.Feiner, J.F.Hughes "Computer graphics: principles and practice", 2nd edition, Addison-Wesley pub., 1990 [15].

In step 205 the histogram H compute the signs and on the basis thereof determines the gain of dark shades and a∈[0, 1]. In step 206 part V is subjected to bilateral filtering by formula (5) with the filter parameters (standard deviations) σD=5, σR=0,1(2n-1). By filtering the receive image Vf. In step 207 calculates the image components D=f(VfV). One of the most preferred options f(Vf,V) is:

where b=3σRk depends on σRfor this σRk=1,2.

At step 208 executes the correction of dark shades in the channel V:

,

.

It should be noted that the steps 207 and 208 may be combined into one and their execution time is reduced by pre-computing and storing the deposits of the two-dimensional coding table (2-D Look-Up Table). 2-D LUT stores the corrected brightness values depending on the source brightness, reflected in the line number table and the bilateral filter, reflected in the number column of the table. Thus reduced and the total time of correction. If RAM size is limited and there is no possibility to store a matrix of size (2n-1)×(2n-1), we can construct a 2-D LUT with thinning and calculate adjusted values using bilinear interpolation to the nearest values of the thinned table. For example, for n=8 using 2-D LUT size 52×52 or 86×86 followed by bilinear interpolation visually indistinguishable from the use of 2-D LUT of size 256×256.

In step 209, the image from the color system is converted into HSV color system RGB.

Figure 3 shows the block diagram of the global contrast. In step 301 determines the lower limit of the range of contrast:

where T1 and T2 are threshold values, the threshold T2 is injected, in order to avoid erroneous image darkening,

In step 302 determines the upper limit of the range of contrast:

In step 303 perform a linear stretching of the RGB values of the image on the whole valid range:

In step 303 mod is liziruut global brightness histogram of N.

Figure 4 shows the block diagram of the algorithm for determining gain dark shades and implementing the simplest tree classifier.

Previously, global brightness histogram of N compute the signs. The entire range of brightness is divided into 3 sub-bands:

,

,

.

Also compute the global maximum of the histogram:

Calculate the following characteristics, normalized in the range [0, 1].

Share dark tones:

The share of medium tones:

The share of light tone:

The share of the shades in the first half of dark tones:

The share of the shades in the second half of dark tones:

The ratio of the maximum of the histogram in dark colors to the global maximum of the histogram:

The ratio of the maximum of the histogram in the midtones to the global maximum of the histogram:

The ratio of the maximum of the histogram in bright colours to the global maximum of the histogram:

The position of the maximum of the histogram in the dark the x tones:

The position of the maximum of the histogram in bright colours:

The choice of features and classifier due to the following reasons. For photos with backlight illumination characterized by large peaks in the dark and/or bright colours and failure in secondary colours. For the low-exposed photo, taken when using the flash, characterized by a large peak in dark colors. The common factor for all the photos with low local contrast in dark colors is the asymmetry of the histogram in the field of dark tones: center masshysteri in dark colors shifted closer to the beginning of the range of brightness.

Figure 5 shows a histogram of a properly exposed pictures 5(a) and pictures with strong backlighting lighting 5(C), as well as their global luminance histograms (5(b) and 5(d), respectively). In the table 6 summarizes the characteristic values and the resulting operation of the classifier gain dark shades for photos with figure 5(a) and 5(C).

7 shows an example of correction: a - original image, b - enhanced image of the proposed method with the bilateral filter, d - image parts, calculated according to the formula (8).

Fig demonstrates one of the advantages of the proposed method improve dark shades before pic is BOM, used in Adobe Photoshop CS (menu Shadow/Highlight): 8(a) is the work of Photoshop CS Shadow/Highlight, 8(b) - the original raw photo, 8(C) - improved offer by way of photography, 8(d) - graphs of the variation of brightness along the line segment straight line AB. Use Adobe Photoshop CS Shadow/Highlight causes clearly visible halos along high contrast boundaries in the application of the proposed method of image adjustment halo is missing.

The proposed method can be implemented in hardware, obtain or print images or software.

The proposed method is applied to improve image quality when printing on the printer.

With minor changes it can also be used to improve the quality of the captured images in digital cameras, mobile phones with digital cameras, digital video cameras.

1. System correction dark shades on the image containing the module's global contrast, the conversion module from the color system RGB module determining gain dark shades, module bilateral filtering module, the correction of dark shades, the module converting the color system RGB memory, which stores the original image, the display device, which displays the result of the correction, moreover, the output module of the global contrast enhancement is associated with the input module to convert the color system RGB output for transmission of the brightness channel of the module converting from RGB coloring connected with the inputs of the module determining the gain dark shades, module, bilateral filtering and correction module darker, and the output for transmission of the color channels of the module converting from RGB coloring connected with the input module converting the color system RGB output module determining gain dark shades associated with the input module, the correction of dark shades, the output module bilateral filter is connected to the input module, the correction of dark shades, the module output correction dark shades associated input module converting the color system RGB output module converting the color system RGB is connected to the input of a display device, the module global contrast is made with the possibility of correction of the global contrast of the image extension conversion from the color of the RGB system is arranged to convert the image from color system RGB three-color system, one component of which is the brightness of the image, and the other two encode the color module converting the color system RGB performed in the possibility of converting from a three-color system, one of the components which is the brightness of the image, and the other two encode color, back color system RGB module determining gain dark shades made with the possibility to calculate the global histogram of the brightness of the image and to determine the gain in dark colors on the basis of the analysis of the characteristics calculated from the global histogram of the brightness of the image, the module bilateral filtering is executed with the ability to perform bilateral filtering of the luminance channel of the image, the correction module dark shades made with the possibility to adjust the dark shades in the luminance channel of the image.

2. The system according to claim 1, characterized in that the display device is designed as printer, monitor, or similar in function to the display device.

3. The correction method is darker in color digital images, comprising the following operations: carry out the correction of the global contrast in the global contrast of the image and transmit the result to the module conversion from the color system RGB, the conversion from the color system RGB convert the image from color system RGB three-color system, one component of which is the brightness of the image, and the other two encode color, and transmit Canastota in the definition of the gain dark shades, in the module bilateral filtering module correction of dark shades, and the color channels are passed to the module converting the color system RGB determine module for determining the coefficient of dark shades gain dark shades by analyzing the characteristics calculated from the global histogram of brightness, and transmit this coefficient in the correction module darker, conduct bilateral filtering of the luminance channel in the module bilateral filtering and transmit the result to the correction module darker, compute module correction dark shades of the image parts, which are a function of the relationship of image brightness and the bilateral filtering, adjusting module correction dark shades dark shades in the luminance channel by adding to the lightness channel works the difference between image detail and brightness on the inversion of brightness and a gain of dark shades, the result is the adjusted brightness values that are passed into the module converting the color system RGB, convert image color system RGB module converting the color system RGB and transmit the result to the display device.

4. The method according to claim 3, characterized in that the image from the color system RGB convert Trajano entou HSV color system.

5. The method according to claim 3, characterized in that conduct bilateral filtering of the luminance channel using superanalogue bilateral filter in which the filtering is carried out first by row and then column of the image.

6. The method according to claim 5, characterized in that conduct bilateral filtering of the luminance channel using superanalogue bilateral filter, which uses the Gaussian function with standard deviations σD=5 and σR=0,1(2n-1), where n is the color depth per channel.

7. The method according to claim 3, characterized in that determines the gain of the dark shades by analyzing characteristics: the proportion of the tones in the shadows, the share of the tones in the first half of the shadows, the share of the shades in the second half of the shadows, the share of shades of grayscale, the share of shades in bright colours, the ratio of the maximum of the histogram in the shadows to the global maximum of the histogram, the ratio of the maximum of the histogram in the midtones to the global maximum of the histogram, the ratio of the maximum of the histogram in bright colours to the global maximum of the histogram, the position of the maximum of the histogram in the shadows, the position of the maximum of the histogram in bright colors.

8. The method according to claim 3, characterized in that calculates the image details, while using the ratio:

D=f(Vf,V)=(2n-1)kV/(Vf+b)

where D is the brightness of the intermediate image parts;

V - the brightness of the original image;

Vf- the brightness of the image in the bilateral filtering brightness;

b=3σRthat σR- setting bilateral filter;

the constant k=1,2, n - color depth per channel.

9. The method according to claim 3, characterized in that the adjusting dark shades in the luminance channel, while using the ratio:

V=fw(V+a(2n-1-V)fb(D-V)),

where D is the brightness of the intermediate image parts;

V - the brightness of the original image;

a - gain dark shades;

n - color depth per channel.

10. The method according to claim 3, characterized in that calculates the image details and correct dark shades, while pre-compute two-dimensional conversion table in which retain the adjusted brightness depending on the brightness before the correction, reflected in the line number table, and the bilateral filter, which is reflected in the number of the table column.



 

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The invention relates to automatic control and computer engineering

FIELD: digital processing of images, possible use for global and local correction of brightness of digital photographs.

SUBSTANCE: system and method for correcting dark tones in digital photographs contain global contrasting module, module for conversion from RGB color system, module for determining dark tone amplification coefficient, bilateral filtration module, dark tone correction module, module for conversion to RGB color system, random-access memory block, displaying device. Global contrasting module is made with possible correction of global image contrast, module for conversion from RGB color system is made with possible conversion of image from RGB color system to three-component color system, one component of which is image brightness, and two others encode color, module for conversion to RGB color system is made with possible conversion from three-component color system, one of components of which is image brightness, and two others encode color, back to RGB color system, module for determining dark tone amplification coefficient is made with possible computation of global image brightness bar graph and can determine dark tone amplification coefficient based on analysis of signs, calculated from global image brightness bar graph, bilateral filtration module is made with possible execution of bilateral filtration of image brightness channel, dark tone correction module is made with possible correction of dark tones in image brightness channel.

EFFECT: absence of halo-effect.

2 cl, 17 dwg

FIELD: methods for removing noise in an image, possible use for improving quality of image.

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EFFECT: simplified noise removal and increased quality of resulting digital image.

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EFFECT: ensured high quality of automatic correction of red-eye effect.

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EFFECT: detection of low quality, out of focus digital images, and their automatic exclusion from the process of printing with account of preset size of print and resolution of print.

6 cl, 4 dwg

FIELD: information technologies.

SUBSTANCE: invention refers to video compression technology, specifically to blocking effect correction filter applied in multilayered video coder/decoder. Decision mode of blocking effect correction filtration intensity is offered for frame containing block set, including the stages as follows: making decision on current block and adjacent block corrected for blocking effect; estimating whether current block and adjacent block are coded by means of internal BL mode; and if at least one either current block or adjacent block is coded by means of mode other than internal BL mode, making decision on preset filtration intensity relative to border between current block and adjacent block; and if both current block and adjacent block are coded by means of internal BL mode, making decision on filtration intensity which is lower than that chosen relative to border.

EFFECT: development of decision mode blocking effect correction filtration intensity for frame containing block set which provides proper choice of blocking effect correction filter intensity according to that whether certain block to which blocking effect correction filter is applied, uses internal base layer (BL) mode in video coder/ decoder based on layer set.

13 cl, 20 dwg

FIELD: physics; image processing.

SUBSTANCE: present invention pertains to image processing, and in particular, to the method of complexing digital multispectral half-tone images. Method of complexing digital multispectral half-tone images, including obtaining the initial images, involves breaking down each initial image to low frequency and high frequency components, separate processing of low and high frequency component images, complexing of the components, based on the principle of weighted summation for each pixel, and formation of the resultant image. Each initial image is subjected to multiple-level decomposition by the Haar wavelet through fast discrete static two-dimensional wavelet-transformation with the objective obtaining an approximate component, which is a low frequency image component, and a family of detail components, which are high frequency image components. The values of the matrix of energy characteristics of pixels are determined at all decomposition levels for each image. All detail components are filtered and the detail components are corrected through adaptive change of the values of the detail components in accordance with the inter-level dynamics of their energy characteristics. The noise microstructure is removed through adaptive threshold cut of the values of detail components on each decomposition level. The correcting brightness function and the correcting contrast function are calculated for each decomposition level, the parameter of which is a value of the approximate component. Brightness of ranges of each decomposition level is smoothed out through transformation of the approximate components by correcting brightness functions. The detail components of the contrast correcting function are transformed. A weight function is calculated for each decomposition level, the parameter of which is a value of the energy characteristic. The component of each synthesised image for each pixel at each decomposition level is calculated by weighted summation of the corresponding components of decomposing initial images using weight functions. All detail components of the synthesised image are filtered, and the detail components are corrected through adaptive change of the values of detail components in accordance with the inter-level dynamics of their energy characteristics. Noise microstructures are eliminated through adaptive threshold cut of the values of detail components at each decomposition level. The brightness correcting function and the contrast correcting function are calculated, the parameter of which is the value of approximate components of the synthesised image. The approximate component of the correcting brightness function is transformed. The detail components of the contrast correcting function are transformed. The synthesised image is formed through reconstruction using reverse fast discrete static two-dimensional wavelet-transformation, applied to the detail components of the synthesised image and approximate component of the synthesised image. The brightness range of the resulting image is matched with parameters of the video system.

EFFECT: obtaining a high quality image, containing informative image elements of the same scene, obtained in different spectral ranges.

9 dwg

FIELD: physics; processing of images.

SUBSTANCE: invention is related to the field of digital X-ray images processing. Input image is exposed to gamma-correction: extraction of square root for approximation of Poisson noise by model of additive noise distributed according to normal law; for multiplicative model of noise logarithmic conversion is performed; single-level wavelet transform of input image is done, on the basis of which wavelet coefficients are partitioned block-by-block, and standard deviation of noise for every block is assessed; prepared block ratings of noise are smoothened and interpolated by size of initial image, which gives continuously changing and locally adapting assessment of noise for the whole image; initial image is exposed to packet stationary wavelet transform by preset number of decay levels; on the basis of noise level assessment calculated at stage 2, coefficients of transform are exposed to processing with adaptive non-linear operator, which performs threshold suppression of noise and separation of image parts; reverse stationary wavelet transform is done, at that produced image with reduced level of noise and highlighted parts is exposed to reverse gamma-transform.

EFFECT: simultaneous suppression of noise and higher contrast of X-ray images.

5 dwg

FIELD: physics, processing of images.

SUBSTANCE: invention concerns numeral photo, and in particular, the analysis of quality of the numeral image. Method of revealing of unitised contortions is offered at JPEG-coding, at which: estimate the size of the coding block concerning the demanded resolution of a press; spot for each boundary of the block the approximate metric of discernability of contortion at the coding block transformation in case, the size of the coding block is a distinguishable human eye; Classify, in a case when discernability of contortions at coding transformation exceeds the predetermined threshold, boundary of the block or as boundary which demands correction for elimination of unitised contortions or as boundary which is not subject to unitised contortions, by application of the binary qualifier to the vector of the characteristic signs calculated by means of use proquantised DCT of coefficients of the adjacent blocks and a matrix of quantisation of the image.

EFFECT: increase of reliability of detection of unitised contortions at use of the underload computing and temporary resources.

4 cl, 4 dwg

FIELD: physics, computation technology.

SUBSTANCE: invention concerns technology of video compression, particularly deblocking filters. Invention claims deblocking filter applied in videocoder/videodecoder based on multiple layers. Process of deblocking filter power (filtration power) selection during deblocking filtration in respect of margin between current block encoded in intra-BL mode and adjoining block involves determination of whether current or adjoining block has coefficients. Filter power is selected as first filter power if current or adjoining block features coefficients; and filter power is selected as second filter power if current or adjoining block does not have coefficients, So that first filter power exceeds second filter power.

EFFECT: enhanced efficiency of video deblocking.

22 cl, 13 dwg

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