The content of the invention
The invention solves technical problem of the prior art, there is provided a kind of large area array sub-meter grade night scene remote sensing image it is fast
Fast joining method.
In order to solve the above-mentioned technical problem, technical scheme is specific as follows:
A kind of quick joining method of large area array sub-meter grade night scene remote sensing image, comprises the following steps:
Step 1:Relative detector calibration
The processing of correction is normalized to the quantized value of original night remote sensing image each pixel spoke monochrome information response,
The each detecting element response difference of sensor is reduced or eliminated, makes response uniformity of the detecting element to spoke brightness;Utilize phase
Relative detector calibration is carried out to the result of radiation calibration;
Step 2:Remove isolated noise
First, initial data is isolated to the information of tri- wave bands of R, G, B, medium filtering is carried out to each wave band, i.e.,
Imed(R, G, B)=medfilt (Iori) (1)
Wherein, IoriFor initial data, ImedFor the image of medium filtering;
Thereafter, isolated noise medium filtering image will be filtered out and carry out binary conversion treatment, i.e.,
Ibw(R, G, B)=im2bw (Imed(R,G,B),thre) (2)
Wherein, IbwFor binary image, thre is the threshold value of binary conversion treatment;
Binary image is multiplied point by point with initial data, i.e.,
Idenoise(i, j)=Ibw(i,j)×Iori(i,j) (3)
Wherein, IdenoiseFor the image after denoising, Idenoise(i, j) is the gray value of the i-th row of image jth row;
Step 3:Based on RPC without control block adjustment
Sift feature point extractions and matching based on GPU are carried out to the overlapping region of multiple spot imaging task neighbour's close-range image,
Multiframe night scene data are carried out using matching result to eliminate error present in RPC without control block adjustment based on RPC;Step
Rapid four:Light and color homogenization processing
The even light of Mask is carried out to night scene image and the even color based on Wallis conversion is handled;
Using the even light of Mask differential techniques, obtained using Gassian low-pass filter method after the background video of raw video using original
Image carries out phase reducing with background video, obtains the image of illuminance distribution, and its phase reducing is using the public affairs shown in formula 6
Formula;
Iout(x, y)=Iin(x,y)-Iback(x,y)+offset (6)
Offset is grayscale shift amount in formula 6;
According to the maximum f of raw video gray levelmax, minimum value fmin, average valueAnd result image greyscale is maximum
Value gmax, minimum value gmin, average valueCarry out divided linear strength;Stretching formula is provided by formula 7:
G (x, y) is even light result image in formula 7, g'(x, y) it is to the image after even light result image stretch processing;
Wallis conversion can be expressed as:
G (x, y) and f (x, y) is respectively the gray value of raw video and Wallis transformation results images in formula 8;mgAnd mfPoint
Not Wei raw video local gray level average and standard deviation;sgAnd sfRespectively result image local gray level average and standard deviation
The desired value of difference;C ∈ [0,1] are the extension constant of image variance;B ∈ [0,1] are the luminance factor of image, as b → 1, shadow
As average is forced to mf, as b → 0, image average is forced to mg;
Step 5:Correction and image resampling are just penetrated based on RPC
The night scene image obtained to multiple spot imaging is carried out just penetrating correction based on RPC, and weight is carried out to the image after correction
Sampling obtains final splicing image.
In the above-mentioned technical solutions, in step 5, it is as follows that just penetrating based on RPC corrects step:
1) angle point object coordinates are calculated
The initial object coordinates of correspondence provided according to the angle point image space coordinate of image four and regularization coefficient are just being calculated with RPC respectively
Geographical coordinates is obtained, and solves initial affine transformation coefficient, then object space point coordinates corresponding to picpointed coordinate is calculated based on RPC;
2) result image is built
Longitude and latitude minimum, maximum are worth to image covering in the ground areas object space plane coordinates according to corresponding to being imaged multiple spot
Scope (lat0~lat1, lon0~lon1), setting orthography resolution ratio gsd, you can calculate image size (W, H):
3) pixel-by-pixel Ergodic Maps to raw video
The each pixel (s, l) of orthography can be calculated by projection formula and arrive object space plane coordinates initial value (lat, lon),
Formula is as follows:
The elevation H of (lat, lon) position is obtained according to dem data, RPC model formations is substituted into and picpointed coordinate is calculated
(x,y);
4) interpolation gray value and assignment
The picpointed coordinate (x, y) obtained by inverse in 3), the interpolation gray scale on raw video;After calculating gray scale p, assignment
Give result image (s, l) position, final output night scene remote sensing splicing image.
In the above-mentioned technical solutions, in step 1), RPC just calculations obtain object space point coordinates and comprised the following steps:
(1) object space plane coordinates initial value (Lon, Lat) is given according to initial affine transformation figure parameters for picpointed coordinate;
(2) dem data is read according to given object space plane coordinates initial value and obtains height value H, corresponding picture is solved using RPC
Point coordinates, new radiation conversion coefficient is solved using picture point and object space point coordinates;
(3) object space plane coordinates is given according to new affine transformation figure parameters for picpointed coordinate, and it is corresponding to read DEM
Height value, solve and finish if the height value solved twice is less than threshold value, otherwise repeatedly said process, calculated until twice
Untill object space elevation difference out is less than threshold value.
In the above-mentioned technical solutions, in step 4), the interpolation uses bilinear interpolation method, and formula is as follows:P=p (i,
j)*(1-dx)*(1-dy)+p(i+1,j)*dx*(1-dy)+p(i+1,j+1)*dx*dy+p(i,j+1)*(1-dx)*dy。
The present invention has following beneficial effect:
The present invention is based on existing image mosaic Processing Algorithm, and the attitude of satellite becomes when taking into full account the imaging of optical satellite multiple spot
Change larger, night scene video imaging object is hot spot and the imaging characteristicses of isolated noise be present, and large area array high-resolution image number
According to the characteristics of big is measured, to raw video progress relative detector calibration, image denoising, based on RPC without control block adjustment, even light
Even color, correction just penetrated based on RPC, and the processing such as image resampling obtains large-scale night scene remote sensing splicing image.
The quick joining method of large area array sub-meter grade night scene remote sensing image provided by the invention, by being carried out to raw video
Relative detector calibration, image denoising, correction just penetrated based on RPC without control block adjustment, light and color homogenization based on RPC, and
The processing such as image resampling obtain large-scale night scene remote sensing splicing image, and have speeded up to the quick of algorithm by GPU
Processing, both ensure that the accuracy of algorithm, and had greatly improved processing speed again, algorithm is simple and easy, easily in project treatment
In directly apply.
Embodiment
The original color image that the present invention obtains sensor carries out relative radiation calibration and obtains the consistent night scene shadow of radiation
Picture, image denoising is carried out for isolated noise, carried out for denoising night scene image based on RPC without control block adjustment, for
Orthography carries out light and color homogenization processing, and just penetrates correction based on RPC, finally several night scene images consistent to color search
Splicing line obtains preferable night scene splicing image.
The present invention is described in detail below in conjunction with the accompanying drawings.
Referring to Fig. 1:A kind of quick joining method of large area array sub-meter grade night scene remote sensing image, comprises the following steps:
Step 1:Relative detector calibration
Relative detector calibration is also known as the normalized of sensor detecting element, is that each pixel spoke monochrome information is rung
The processing of correction is normalized in the quantized value (DN) answered, and reduces or eliminates each detecting element response difference of sensor, make spy
Survey response uniformity of the element to spoke brightness.Relative detector calibration is carried out using the result of relative radiometric calibration.
Step 2:Remove isolated noise
First, initial data is isolated to the information of tri- wave bands of R, G, B, medium filtering is carried out to each wave band, i.e.,
Imed(R, G, B)=medfilt (Iori) (1)
Wherein, IoriFor initial data, ImedFor the image of medium filtering.Because the highlighted noise in image is isolated makes an uproar
Point, therefore the algorithm of medium filtering can filter out the highlighted noise in image well.
Thereafter, isolated noise medium filtering image will be filtered out and carry out binary conversion treatment, i.e.,
Ibw(R, G, B)=im2bw (Imed(R,G,B),thre) (2)
Wherein, IbwFor binary image, thre is the threshold value of binary conversion treatment.By binary conversion treatment, can isolate
Background noise and foreground information.
Binary image is multiplied point by point with initial data, i.e.,
Idenoise(i, j)=Ibw(i,j)×Iori(i,j) (3)
Wherein, IdenoiseFor the image after denoising, Idenoise(i, j) is the gray value of the i-th row of image jth row.Now obtain
Denoising image not only remove image dark place ambient noise and isolated highlighted noise, while remain the brighter place of image
High-frequency information.
Step 3:Based on RPC without control block adjustment
Rational function model is that picpointed coordinate (r, c) is expressed as with corresponding topocentric coordinates (X, Y, Z) as independent variable
Multinomial ratio, i.e.,
(r in formulan,cn) and (Xn,Yn,Zn) represent that pixel coordinate (r, c) and topocentric coordinates (X, Y, Z) contract through translation respectively
Normalized coordinates after putting, between value is -1.0~+1.0, wherein polynomial coefficient is referred to as the coefficient of rational function
(rational function coefficient, RPC), can be established between image coordinate system and earth axes by RPC and closed
System.
In the case that control participates on no ground, satellite attitude parameters and the RPC moulds of orbit parameter generation are directly utilized
Type often contains larger systematic error, have impact on image positioning precision so that more scape images just penetrate correction after overlapping region without
Method overlaps exactly, it is therefore desirable to is imaged the night scene image obtained for multiple spot and carries out based on RPC without control regional network
Adjustment.Need to carry out Feature Points Matching for night scene image overlap area during adjustment, using with anti-rotation consistency
Sift is matched, in order to realize that the quick splicing of night scene image, can be by routine based on CPU using the sift matchings based on GPU
Sift match times shorten about 140 times.
Using acquisition point-to-multipoint of the same name imaging obtain night scene image carry out based on image space without control block adjustment,
Error existing for determining single scape image RPC models to be spliced simultaneously, it ensure that and eliminate after error corresponding to the image of overlapping region
Atural object there's almost no relative geographical position deviation.
Step 4:Light and color homogenization processing
Due to the image of the time of image capturing, shooting angle, external light source, atmospheric attenuation and some other factor,
Different degrees of difference on color be present in the night scene image that can cause to obtain, thus night scene image is carried out the even light of Mask and
The even color processing of Wallis.
Using the even light of Mask differential techniques, obtained using Gassian low-pass filter method after the background video of raw video using original
Image carries out phase reducing with background video, you can obtains the image of illuminance distribution, its phase reducing can use the institute of formula 6
The formula shown.
Iout(x, y)=Iin(x,y)-Iback(x,y)+offset (6)
Offset is grayscale shift amount in formula 6.
In order to increase adjacent thin portion contrast, the overall contrast of whole image is improved, it is necessary to divide the image after processing
Section linear stretch processing.According to the maximum f of raw video gray levelmax, minimum value fmin, average valueAnd result image
Gray scale maximum gmax, minimum value gmin, average valueCarry out divided linear strength.Stretching formula is provided by formula 7:
G (x, y) is even light result image in formula 7, g'(x, y) it is to the image after even light result image stretch processing.This
Kind divided linear strength need not add additional parameter, and image greyscale dynamic range after processing can be restored into raw video
In tonal range.
Need to carry out based on Wallis conversion colors equilibrium treatment side to adjust the color balance between night scene remote sensing image
Method, Wallis become transducing and suppress noise again while original sub-meter grade image local contrast is strengthened, and have local auto-adaptive work(
Energy.Wallis conversion can be expressed as:
G (x, y) and f (x, y) is respectively the gray value of raw video and Wallis transformation results images in formula 8;mgAnd mfPoint
Not Wei raw video local gray level average and standard deviation (variance);sgAnd sfRespectively result image local gray level average and
The desired value of standard deviation;C ∈ [0,1] are the extension constant of image variance;B ∈ [0,1] are the luminance factor of image, when b → 1
When, image average is forced to mf, as b → 0, image average is forced to mg。
Step 5:Correction and image resampling are just penetrated based on RPC
Projected centered on large area array night scene remote sensing image, and certain inclination angle during image capturing be present, in order to eliminate due to
Deformation caused by image inclination and hypsography etc. carries out just penetrating based on RPC, it is necessary to be imaged the night scene image obtained to multiple spot
Correct, and resampling is carried out to the image after correction and obtains final splicing image.Just penetrating wherein based on RPC corrects step such as
Under:
1) angle point object coordinates are calculated
The initial object coordinates of correspondence provided according to the angle point image space coordinate of image four and regularization coefficient are just being calculated with RPC respectively
To geographical coordinates, and solve initial affine transformation coefficient.Hereafter object space point corresponding to picpointed coordinate is calculated based on RPC again to sit
Mark.Following steps can specifically be used:
(1) object space plane coordinates initial value (Lon, Lat) is given according to initial affine transformation figure parameters for picpointed coordinate;
(2) dem data is read according to given object space plane coordinates initial value and obtains height value H, corresponding picture is solved using RPC
Point coordinates, new radiation conversion coefficient is solved using picture point and object space point coordinates;
(3) object space plane coordinates is given according to new affine transformation figure parameters for picpointed coordinate, and it is corresponding to read DEM
Height value, solve and finish if the height value solved twice is less than threshold value, otherwise repeatedly said process, calculated until twice
Untill object space elevation difference out is less than threshold value.
2) result image is built
Longitude and latitude minimum, maximum are worth to image covering in the ground areas object space plane coordinates according to corresponding to being imaged multiple spot
Scope (lat0~lat1, lon0~lon1), setting orthography resolution ratio gsd, you can calculate image size (W, H):
3) pixel-by-pixel Ergodic Maps to raw video
The each pixel (s, l) of orthography can be calculated by projection formula and arrive object space plane coordinates initial value (lat, lon),
Formula is as follows:
The elevation H of (lat, lon) position is obtained according to dem data, RPC model formations is substituted into and image space coordinate is calculated
(x,y)。
4) interpolation gray value and assignment
The picpointed coordinate (x, y) obtained by inverse in 3), the interpolation gray scale on raw video.Interpolation is divided into closest to interpolation
Method, three kinds of methods of bilinear interpolation method and bi-cubic interpolation method are public using bilinear interpolation method in order to take into account efficiency and precision
Formula is as follows:
P=p (i, j) * (1-dx) * (1-dy)+p (i+1, j) * dx* (1-dy)+p (i+1, j+1) * dx*dy+p (i, j+1) *
(1-dx)*dy
After calculating gray scale p, result image (s, l) position is assigned to, the remote sensing of final output night scene splices image (referring to figure
2 and 3).
The quick joining method of large area array sub-meter grade night scene remote sensing image provided by the invention, by being carried out to raw video
Relative detector calibration, image denoising, correction just penetrated without control block adjustment, light and color homogenization, based on RPC based on RPC, and
The processing such as image resampling obtain large-scale night scene remote sensing splicing image, and have speeded up to the quick of algorithm by GPU
Processing, both ensure that the accuracy of algorithm, and had greatly improved processing speed again, algorithm is simple and easy, easily in project treatment
In directly apply.
The satellite launched with reference to Chang Guang satellite technologies Co., Ltd --- exemplified by the star of video 03, describe night scene shadow in detail
The denoising of picture and enhancing processing method.
The star of video 03 uses main square as 3200mm video cameras, and the resolution ratio of substar is 0.92m, the single frames night scene of collection
Image size is 12000 × 5000 pixels.For the star of video 03 on April 1st, 2017,5 points were taken the photograph London night scene, shooting point longitude and latitude for 43 minutes
It is 51.4628 ° to spend for -0.179 ° of longitude, latitude.The big face of the present invention is illustrated for this multiple spot night scene video imaging task
The quick joining method of battle array sub-meter grade night scene remote sensing image, this method comprise the following steps:
Step 1:Relative radiation calibration
Relative detector calibration is carried out to night scene image according to relative radiometric calibration result.
Step 2:Isolated noise denoising
First, initial data is isolated to the information of tri- wave bands of R, G, B, R, G, B size are respectively 3000 × 1250
Pixel, 6000 × 2500 pixels and 3000 × 1250 pixels, medium filtering is carried out using formula (1) to each wave band, gone
Except the filtered image I of highlighted noisemed(R,G,B)。
Thereafter, isolated noise medium filtering image I will be filtered outmed(R, G, B) carries out binary conversion treatment, root according to formula (2)
According to the view data of acquisition, it is 6 to set binary-state threshold thre, so as to obtain binary image Ibw.Pass through binary conversion treatment, energy
Background noise and foreground information is enough effectively separated.By binary image and initial data according to formula (3) carry out by
Point is multiplied, and obtains the image I after denoisingdenoise。
The denoising image now obtained not only removes the ambient noise of the dark place of image and isolated highlighted noise, protects simultaneously
The high-frequency information at the brighter place of image is stayed.
Step 3:Based on RPC without control block adjustment
Sift feature point extractions and matching based on GPU are carried out to the overlapping region of multiple spot imaging task neighbour's close-range image,
Multiframe night scene data are carried out using matching result to eliminate error present in RPC without control block adjustment based on RPC.
Step 4:Light and color homogenization processing
The dodging based on Mask principles is carried out for multiframe night scene image and the even color based on Wallis conversion is handled
Obtain the consistent night scene remote sensing image of color.
Step 5:Correction and resampling are just penetrated based on RPC
The image point displacement as caused by imaging angle and hypsography, and root are eliminated by the correction processing of just penetrating based on RPC
Obtain splicing image size according to the object space range computation of image, and for splicing image node-by-node algorithm its in single scape night scene image
Position simultaneously carries out bilinear interpolation and obtains the night scene remote sensing image of final multiple spot splicing.
Obviously, above-described embodiment is only intended to clearly illustrate example, and is not the restriction to embodiment.It is right
For those of ordinary skill in the art, can also make on the basis of the above description it is other it is various forms of change or
Change.There is no necessity and possibility to exhaust all the enbodiments.And the obvious change thus extended out or
Among changing still in the protection domain of the invention.