CN103747225A - High-dynamic-range image dual-screen display method based on color space switching - Google Patents

Abstract

The invention relates to a high-dynamic-range image dual-screen display method based on color space switching. The method is characterized by comprising the following steps: S1, calculating a high-dynamic-range image and converting into an RGB (Red Green Blue) space image; S2, converting the RGB space image in the step S1 into an HSL (High Speed Logic) space image, and finishing the separation of brightness and tone; S3, performing separate self-adaptive logarithm mapping on the brightness L of the HSL space image in the step S2, finishing compression of the brightness, and enhancing the saturation S; S4, converting the HSL space image in the step S3 into an RGB space image; S5, performing front-back panel image segmentation on the RGB space image in the step S4; S6, performing dual-screen segmented display of front and back panel images generated in the step S5 on an LCD-FED (Liquid Crystal Display-Field Emission Display) dual-screen display screen. By adopting the high-dynamic-range image dual-screen display method, the problem of color shift is solved, and the detail expression capability is enhanced greatly.

Description

High dynamic range images double screen display packing based on color space conversion

Technical field

The present invention relates to high-dynamics image processing and show field, especially a kind of high dynamic range images double screen display packing based on color space conversion with the double screen of high dynamic range images.

Background technology

In the last few years, more and more for the research of high dynamic range images, high dynamic range images was a kind of image that can rediscover scene brightness scope.Its brightness range is from black night evening to sunlight fierce daytime, and dynamic range even surpasses 1010:1.Brightness on a large scale compared to high dynamic range images, the dynamic range of current main-stream display device is just very little, nowadays the dynamic range of main flow display device is that 400:1 is to 600:1, the dynamic range of partial display equipment can reach 1500:1, even if therewith, remain and do not reach the requirement that shows high dynamic range images far away.For the solution of this problem, be to carry out tone mapping on the one hand, these algorithms are roughly divided into two large classes: global map algorithm and local mapping algorithm.Tone-mapping algorithm can be compressed into low dynamic range echograms by high dynamic range images mapping, and for common display equipment.No matter be global map algorithm, or local mapping algorithm, but these algorithms all can lose the part details of image, and all for the object of the level visual rendition of the high dynamic range images of achromaticity (gray scale), design, after not considering that image brightness scope is compressed, colour gamut is also compressed, causes the color of image visually to change, and produces colour cast problem.Be to adopt double screen to show on the other hand, double screen shows the dynamic display capabilities that can obviously improve display system, can carry out better details demonstration.

For colour cast problem, a lot of solutions have been proposed, but the MSRCR algorithm calculation of complex that people proposes such as these algorithms all have some shortcomings part, Rahma, and loss of detail is more; Algorithm based on histogram equalization has obvious distortion; Quick brightness adjustment algorithm based on point shows not good enough in integral image harmony.

Existing double screen displaying scheme comprises LCD-projector, LCD-LED and LCD-Optics.LCD-projector scheme is bulky, cannot be commonly public use.LCD-LED scheme but has that LED particle is large, easily produce the problems such as interferences between pixel limits.The people such as GabrieleGuarnieri propose the Double liquid crystal display system of LCD-LCD structure, but this system brightness is lower, need high brightness backlights support, and refresh rate is also difficult to improve.The people such as Patrick Ledda propose the Double-Screen Display System of LCD-Optics structure, but this systems bulky, visual angle is limited.

Summary of the invention

In view of this, the object of this invention is to provide a kind of high dynamic range images double screen display packing based on color space conversion, colour cast problem and the details for the moving range image of height, processed show not enough problem.

The present invention adopts following scheme to realize: a kind of high dynamic range images double screen display packing based on color space conversion, it is characterized in that, and comprise the following steps:

S1: high dynamic range images is calculated and converts rgb space image to;

S2: the rgb space image in step S01 is converted to HSL spatial image, completes the separated of brightness and tone;

S3: the brightness L for the HSL spatial image in step S02 carries out independent self adaptation logarithmic mapping, the compression that completes brightness is processed, and meanwhile, to saturation, S strengthens;

S4: the HSL spatial image in step S03 is converted to rgb space image;

S5: the rgb space image in step S04 is carried out to front and back panel image and cut apart;

S6: utilize the front and back panel image generating in step S05 to carry out double screen in LCD-FED Double-Screen Display System and cut apart demonstration.

In an embodiment of the present invention, the concrete grammar of described step S1 is: if e is 0, and r=g=b=0.0, otherwise: r=R*2^ (e-128-8), g=G*2^ (e-128-8), b=B*2^ (e-128-8); Wherein (R, G, B, E) is the single pixel value of RGBE image, and (r, g, b) is the single pixel value of rgb space image.

In an embodiment of the present invention, described step S2 concrete grammar is: adopt sub-pixel corresponding conversion method by rgb space image value (r, g, b) be converted to HSL spatial image value (h, s, l), complete image conversion to HSL space by rgb space, concrete switch process is as follows:

S21: transfer rgb pixel value to floating point values between (0,1);

S22: find out maximum max and minimum value min in rgb pixel value, and calculate brightness

S23: if max=min, S is defined as 0 so, and H is undefined and be defaulted as 0; Otherwise, according to brightness L, calculate saturation S; Formula is: $s=\left\{\begin{array}{c}0,l=0\mathrm{or}\max =\min \\ \frac{\max -\min }{2l},0<l\&le;\frac{1}{2}\\ \frac{\max -\min }{2-2l},l>\frac{1}{2}\end{array}\right.;$

S24: calculate tone H, formula is:

In an embodiment of the present invention, the self adaptation logarithmic mapping formula in described step S03 is:

$L_d(x,y)=\frac{L_{d\max }(x,y)\&times;0.01}{{\log }_{10}(L_{w\max }+1)}\&times;\frac{{\log }_{10}(L_w(x,y)+1)}{{\log }_{10}[2+\left({\left(\frac{L_w(x,y)}{L_{w\max }}\right)}^{\frac{{\log }_{10}\left(b\right)}{{\log }_{10}\left(0.5\right)}}\right)\&times;8]},$ Wherein, L _dmaxthe maximum brightness value that can show for display device; L _w(x, y) is the brightness value of each pixel; L _wmaxfor image brightness maximum; L _d(x, y) is the brightness value of the rear image of mapping, and parameter b is adjustable parameters, affects the overall brightness of image, and span is (0.5,1.0).

In an embodiment of the present invention, after the mapping calculation of described brightness L completes, carry out a non-linear gamma and proofread and correct, brightness L is carried out to the power exponent computing that an index is 1/2.2.

In an embodiment of the present invention, saturation S strengthened to formula be in described step S03: S'=α S, S' is the saturation after strengthening, α is saturation enhancer.

In an embodiment of the present invention, described step S5 is specially: the thought based on LCIS algorithm, and backpanel image is calculated by the square root of former figure, and frontpanel image is divided by and is calculated by former figure and backpanel image.

In an embodiment of the present invention, described backpanel image is for the demonstration of FED backlight, and described frontpanel image is for LCD Display panel.

The main feature of the inventive method is as follows:

High-dynamics image is carried out to the conversion of color space, isolate color and brightness, process separately brightness value, we disregard the colouring information of separating from high-dynamics image, just can effectively reduce colour cast degree.In conjunction with LCD-FED double screen, show again, further improved the display capabilities of high-dynamics image details.When image color can be retained, retain the abundanter details of image like this.

Accompanying drawing explanation

Fig. 1 is method flow diagram of the present invention;

Fig. 2 a is high dynamic range original graph;

Fig. 2 b is HSL space original graph;

Fig. 3 a is that HSL space L divides spirogram;

Fig. 3 b is figure (b=0.8) after L component self adaptation logarithmic mapping;

Fig. 4 a is direct RGB logarithmic mapping result figure;

Fig. 4 b is histogram equalization algorithm design sketch;

Fig. 4 c is HSL of the present invention space conversion effect figure;

Fig. 5 a is FED backlight demonstration figure of the present invention;

Fig. 5 b is LCD demonstration figure of the present invention;

Fig. 6 is the final double screen demonstration of the present invention figure.

Embodiment

For making object of the present invention, technical scheme and advantage clearer, below will, by specific embodiment and relevant drawings, the present invention be described in further detail.

As shown in Figure 1, the invention provides a kind of high dynamic range images double screen display packing based on color space conversion, comprise the following steps:

S1: by high dynamic range images RGBE(as shown in Figure 2 a) calculate and convert rgb space image to;

S2: the rgb space image in step S01 is converted to HSL spatial image (as shown in Figure 2 b), completes the separated of brightness and tone;

S3: the brightness L for the HSL spatial image in step S02 carries out independent self adaptation logarithmic mapping, the compression that completes brightness is processed, and meanwhile, to saturation, S strengthens accordingly;

S4: the HSL spatial image in step S03 is converted to rgb space image; Step S2 is carried out to reverse operating, HSL spatial image is rotated back into rgb space;

S5: the rgb space image in step S04 is carried out to front and back panel image and cut apart;

S6: utilize the front and back panel image generating in step S05 to carry out double screen in LCD-FED Double-Screen Display System and cut apart demonstration.

The expansion .hdr by name of RGBE file; So-called E, is exactly index, and each passage of RGBE file is 8bit data type, and 4 passages come to 32bit; RGBE formatted file cannot directly shine upon processing, need change.The concrete grammar of described step S1 is: if e is 0, and r=g=b=0.0, otherwise: r=R*2^ (e-128-8), g=G*2^ (e-128-8), b=B*2^ (e-128-8); Wherein (R, G, B, E) is the single pixel value of RGBE image, and (r, g, b) is the single pixel value of rgb space image.

Described step S2 concrete grammar is: adopt sub-pixel corresponding conversion method that rgb space image value (r, g, b) is converted to HSL spatial image value (h, s, l), complete image conversion to HSL space by rgb space, concrete switch process is as follows:

S21: transfer rgb pixel value to floating point values between (0,1);

S22: find out maximum max and minimum value min in rgb pixel value, and calculate brightness

S23: if max=min represents grey, S is defined as 0 so, and H is undefined and be defaulted as 0; Otherwise, according to brightness L, calculate saturation S; Formula is: $s=\left\{\begin{array}{c}0,l=0\mathrm{or}\max =\min \\ \frac{\max -\min }{2l},0<l\&le;\frac{1}{2}\\ \frac{\max -\min }{2-2l},l>\frac{1}{2}\end{array}\right.;$

S24: calculate tone H, formula is:

hue angle h ∈ [0,360), and h=0 presentation video is grey, and s, l is saturation and brightness, its span is all in [0,1].

Self adaptation logarithmic mapping formula in described step S03 is:

$L_d(x,y)=\frac{L_{d\max }(x,y)\&times;0.01}{{\log }_{10}(L_{w\max }+1)}\&times;\frac{{\log }_{10}(L_w(x,y)+1)}{{\log }_{10}[2+\left({\left(\frac{L_w(x,y)}{L_{w\max }}\right)}^{\frac{{\log }_{10}\left(b\right)}{{\log }_{10}\left(0.5\right)}}\right)\&times;8]},$ Wherein, L _dmaxfor the maximum brightness value that display device can show, as the quantization parameter that shows use, conventionally get L _dmax=100; L _w(x, y) is the brightness value of each pixel; L _wmaxfor image brightness maximum; L _d(x, y) is the brightness value of the rear image of mapping.During logarithmic transformation, the selection of radix directly affects the quality for the treatment of effect, and radix regulates formula as follows:

parameter b is adjustable parameters, affects the overall brightness of image, and span is generally (0.5,1.0).Experiment discovery, the treatment effect to most of high-dynamics images during b=0.8 is best.

After the mapping calculation of described brightness L completes, also need to carry out a non-linear gamma and proofread and correct, brightness L is carried out to the power exponent computing that an index is 1/2.2.As shown in Fig. 3 a and 3b, Fig. 3 is that HSL space L divides spirogram, and Fig. 3 b is figure (b=0.8, gamma=1/2.2) after L component self adaptation logarithmic mapping.

Saturation S strengthened to formula be in described step S03: S'=α S, S' is the saturation after strengthening, α is saturation enhancer, general α=1.6.After brightness mapping and saturation enhancing, we rotate back into rgb space by image again by HSL space.As shown in Fig. 4 a, 4b and 4c, in Fig. 4 a, directly the image of RGB conversion differs larger with former figure on integral color, in Fig. 4 b, the performance of algorithm of histogram equalization color is better than Fig. 4 a, but red circle partly has certain distortion, Fig. 4 c is the effect through the conversion of HSL space, image is not only very nearly the same in color with former figure, and there will not be problem of dtmf distortion DTMF.

In order to obtain better display effect, carry out more image detail demonstration.The present invention adopts LCD-FED double screen high dynamic range display system to show processed image, double screen shows that the front and back screen must carry out input picture cuts apart, existing double screen partitioning algorithm is LCIS algorithm, LCIS algorithm is that high dynamic range images is divided into basic brightness layer and levels of detail, but the hierarchical algorithm calculation of complex of LCIS, operand is large, and the efficiency of processing image is very low.The present invention is based on the thought of LCIS (Low Curvature Image Simplifier) algorithm, adopt a kind of simple partitioning algorithm to carry out layering to image, improved image processing speed, rear board (backlight) image is calculated by the square root of former figure, and front panel (LCD panel) image is divided by and is calculated by former figure and rear board (backlight) image.Specific algorithm formula is as follows: L _b(x, y)=F (L _in(x, y)), wherein, the value that image is located at (x, y) is L _w(x, y), the brightness value of FED backlight is L _b(x, y), the brightness value of front panel LCD is L _f(x, y).Function F (L _in(x, y)) be a square root.As shown in Fig. 5 a and 5b, Fig. 5 a is FED backlight demonstration figure, and Fig. 5 b is LCD demonstration figure.Described rear board (backlight) image is for the demonstration of FED backlight, and described front panel (LCD panel) image, for LCD Display panel, as shown in Figure 6, finally obtains synthetic image.

Above-listed preferred embodiment; the object, technical solutions and advantages of the present invention are further described; institute is understood that; the foregoing is only preferred embodiment of the present invention; not in order to limit the present invention; within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (8)

1. the high dynamic range images double screen display packing based on color space conversion, is characterized in that, comprises the following steps:

S1: high dynamic range images is calculated and converts rgb space image to;

S2: the rgb space image in step S01 is converted to HSL spatial image, completes the separated of brightness and tone;

S3: the brightness L for the HSL spatial image in step S02 carries out independent self adaptation logarithmic mapping, the compression that completes brightness is processed, and meanwhile, to saturation, S strengthens;

S4: the HSL spatial image in step S03 is converted to rgb space image;

S5: the rgb space image in step S04 is carried out to front and back panel image and cut apart;

S6: utilize the front and back panel image generating in step S05 to carry out double screen in LCD-FED Double-Screen Display System and cut apart demonstration.

2. the high dynamic range images double screen display packing based on color space conversion according to claim 1, it is characterized in that, the concrete grammar of described step S1 is: if e is 0, r=g=b=0.0, otherwise: r=R*2^ (e-128-8), g=G*2^ (e-128-8), b=B*2^ (e-128-8); Wherein (R, G, B, E) is the single pixel value of RGBE image, and (r, g, b) is the single pixel value of rgb space image.

3. the high dynamic range images double screen display packing based on color space conversion according to claim 1, it is characterized in that, described step S2 concrete grammar is: adopt sub-pixel corresponding conversion method by rgb space image value (r, g, b) be converted to HSL spatial image value (h, s, l), complete image conversion to HSL space by rgb space, concrete switch process is as follows:

S21: transfer rgb pixel value to floating point values between (0,1);

S22: find out maximum max and minimum value min in rgb pixel value, and calculate brightness

S23: if max=min, S is defined as 0 so, and H is undefined and be defaulted as 0; Otherwise, according to brightness L, calculate saturation S; Formula is: $s=\left\{\begin{array}{c}0,l=0\mathrm{or}\max =\min \\ \frac{\max -\min }{2l},0<l\&le;\frac{1}{2}\\ \frac{\max -\min }{2-2l},l>\frac{1}{2}\end{array}\right.;$

S24: calculate tone H, formula is:

4. the high dynamic range images double screen display packing based on color space conversion according to claim 1, is characterized in that: the self adaptation logarithmic mapping formula in described step S03 is:

$L_d(x,y)=\frac{L_{d\max }(x,y)\&times;0.01}{{\log }_{10}(L_{w\max }+1)}\&times;\frac{{\log }_{10}(L_w(x,y)+1)}{{\log }_{10}[2+\left({\left(\frac{L_w(x,y)}{L_{w\max }}\right)}^{\frac{{\log }_{10}\left(b\right)}{{\log }_{10}\left(0.5\right)}}\right)\&times;8]},$ Wherein, L _dmaxthe maximum brightness value that can show for display device; L _w(x, y) is the brightness value of each pixel; L _wmaxfor image brightness maximum; L _d(x, y) is the brightness value of the rear image of mapping, and parameter b is adjustable parameters, affects the overall brightness of image, and span is (0.5,1.0).

5. the high dynamic range images double screen display packing based on color space conversion according to claim 4, it is characterized in that: after the mapping calculation of described brightness L completes, carry out a non-linear gamma and proofread and correct, brightness L is carried out to the power exponent computing that an index is 1/2.2.

6. the high dynamic range images double screen display packing based on color space conversion according to claim 1, it is characterized in that, saturation S strengthened to formula be in described step S03: S'=α S, S' is the saturation after strengthening, α is saturation enhancer.

7. the high dynamic range images double screen display packing based on color space conversion according to claim 1, it is characterized in that, described step S5 is specially: the thought based on LCIS algorithm, backpanel image is calculated by the square root of former figure, and frontpanel image is divided by and is calculated by former figure and backpanel image.

8. the high dynamic range images double screen display packing based on color space conversion according to claim 7, is characterized in that: described backpanel image is for the demonstration of FED backlight, and described frontpanel image is for LCD Display panel.

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