用一個點圍繞同心圓創建邊緣圖像的直方圖[Matlab]

Question

我有一個邊緣圖像[通過應用Canny邊緣檢測器得到]。在此我有一個關鍵點。我希望以關鍵點爲中心，以同心圓（圓形+放射狀）的方格獲得圖像的直方圖，類似於CD或DVD中的扇區。

我打算這樣做： 1.在邊緣圖像上應用二進制掩碼 2.對具有不同半徑的圖像應用圓形+徑向掩碼。 3.總結每個半徑的所有像素值。

我被卡住的部分是2.我怎樣才能同時獲得圓形+徑向面罩？爲了使它更清晰 - 假設我有一個圖像 - 我想通過在週期角度處繪製沿半徑的同心圓和線來將它分成兩個分箱。

編輯

通過@anandr就像一些小修改魅力所提供的代碼。但是，我們現在有一些Angbins和Radbins，我們可以將他們兩個都分成一組垃圾箱，如圖中我所鏈接的here？原因是我們不得不將其平化爲在我們正在掃描的每個倉中具有值1的數量像素值的直方圖。這可能嗎？請告訴我！ 謝謝！

EDIT 2

對於@anandr了前面的代碼，如果我有

agg(ia,ir)=sum(abs(tImg(:))); 

的tImg = cat(3,tR,tG,tB);部分之後？ 這會給我在那個特定bin中值爲1的像素的數量嗎？

Answer 1

由於@Parag建議，您必須檢查每個像素相對於關鍵點的距離和角度。然後，您可以使用histc函數爲您的像素分配適當的箱號。檢查下面

function [RadialBins,AngularBins] = MakeRadCircMask(ImgRows,ImgCols, KeyRow,KeyCol, DistanceEdges, AngleEdges) 
    % [RadialMask,AngularMask] = MakeRadCircMask(ImgRows,ImgCols, KeyRow,KeyCol, DistanceEdges, AngleEdges) 
    % RADIALBINS is the distance bin number for bin edges specified in DISTANCEEDGES 
    % ANGULARBINS is the distance bin number for bin edges specified in ANGLEEDGES 
    % For pixels outside of min(DISTANCEEDGES):max(DISTANCEEDGES) -1 returned 
    % For pixels outside of min(ANGLEEDGES):max(ANGLEEDGES) -1 returned 
    x     = (1:ImgCols)-KeyCol; 
    y     = (1:ImgRows)-KeyRow; 
    [xx,yy]    = meshgrid(x , y); 
    d     = sqrt(xx.^2 + yy.^2); 
    a     = atan2(yy , xx); 
    [n,bin]    = histc(d,DistanceEdges); 
    RadialBins   = -ones(ImgRows,ImgCols); 
    RadialBins(bin>0) = bin(bin>0); 
    [n,bin]    = histc(a,AngleEdges*pi/180); 
    AngularBins   = -ones(ImgRows,ImgCols); 
    AngularBins(bin>0) = bin(bin>0); 
end 

% now we test the masks 

%Initial data 
ImgRows  = 100; 
ImgCols  = 200; 
DstEdges = 0:10:150; 
AngEdges = -180:30:180; 

NDstBins = length(DstEdges)-1; 
NAngBins = length(AngEdges)-1; 

%Create checkerboard image 
r   = 1:ImgRows; 
c   = 1:ImgCols; 
[cc,rr]  = meshgrid(c,r); 
Img   = (-1).^(round(rr/3) + round(cc/3)); 
Img(Img<0) = 0; 

% Calculate bins 
[RadialBins,AngularBins] = MakeRadCircMask(ImgRows,ImgCols, 50,150, DstEdges, AngEdges); 

% show the cartoon ;o) 
figure; 
subplot(2,2,1); imagesc(RadialBins); axis equal; axis tight; title('Radial bins'); 
subplot(2,2,2); imagesc(AngularBins); axis equal; axis tight; title('Angular bins'); 
subplot(2,2,3); imagesc(Img);   axis equal; axis tight; title('Original image'); 
subplot(2,2,4); imagesc(Img);   axis equal; axis tight; title('Selection image'); 
%return; 

for ir=1:NDstBins 
    % compute the radiaal mask 
    rMask  = RadialBins==ir; 

    for ia=1:NAngBins 
     % compute the angular mask 
     aMask  = AngularBins==ia; 

     % do some stuff with the images 
     tR    = zeros(ImgRows,ImgCols); 
     tG    = zeros(ImgRows,ImgCols); 
     tB    = zeros(ImgRows,ImgCols); 

     tR(aMask)  = Img(aMask); 
     tG(rMask)  = Img(rMask); 
     tB(rMask&aMask) = Img(rMask&aMask); 
     tR(rMask&aMask) = 0; 
     tG(rMask&aMask) = 0; 

     tImg   = cat(3,tR,tG,tB); 

     % and display the results 
     subplot(2,2,4); imagesc(tImg); axis equal; axis tight; 
     title({ 
      sprintf('Radial bin %d of %d (%.1f to %.1f);',ir,NDstBins,DstEdges(ir),DstEdges(ir+1)) 
      sprintf('Angular bin %d of %d (%.1f to %.1f);',ia,NAngBins,AngEdges(ia),AngEdges(ia+1)) 
      }) 
     drawnow; 
    end 

end 

UPD的代碼：代碼更新以處理外的範圍中的像素

EDIT1 變形是容易的，如果你需要可變數量的用於每個徑向條紋角度倉。然而，在這種情況下，每個徑向倉的扇區從一個開始編號到適當數量的角倉。所以如果你需要處理一個特定的扇區，你必須檢查徑向掩模和角度掩模。

function [RadialBins,AngularBins] = RadialGrid(ImgRows,ImgCols, KeyRow,KeyCol, DistanceMin,DistanceMax, NAngleBins,NDistanceBins) 
    % Grid = RadialGrid(ImgRows,ImgCols, KeyRow,KeyCol, DistanceMin,DistanceMax, NAngleBins,NDistanceBins) 
    % for details see http://stackoverflow.com/questions/19485118/creating-a-histogram-of-edge-image-with-concentric-circles-around-one-point-mat/19487198?noredirect=1#comment28938533_19487198 
    % 
    if ~isscalar(NDistanceBins) 
     error('NDISTANCEBINS must be scalar'); 
    end 
    if isscalar(NAngleBins) 
    NAngleBins   = ones(1,NDistanceBins)*NAngleBins; 
    end 
    if length(NAngleBins)~=NDistanceBins 
     error('NANGLEBINS must be scalar or vector of NDISTANCEBINS elements'); 
    end 

    DistanceEdges  = linspace(DistanceMin,DistanceMax,NDistanceBins+1); 
    x     = (1:ImgCols)-KeyCol; 
    y     = (1:ImgRows)-KeyRow; 
    [xx,yy]    = meshgrid(x , y); 
    d     = sqrt(xx.^2 + yy.^2); 
    a     = atan2(yy , xx); 
    [n,bin]    = histc(d,DistanceEdges); 
    RadialBins   = -ones(ImgRows,ImgCols); 
    RadialBins(bin>0) = bin(bin>0); 
    RadialBins(RadialBins>NDistanceBins) = -1; 
    AngularBins   = zeros(size(RadialBins))-1; 
    for kk=1:NDistanceBins 
    AngleEdges   = linspace(-180,+180,NAngleBins(kk)+1); 
    [n,bin]    = histc(a,AngleEdges*pi/180); 
    idx     = (bin>0) & (RadialBins==kk); 
    AngularBins(idx) = bin(idx); 
    end 
end 

ImgRows   = 400; 
ImgCols   = 400; 
NDistanceBins = 5; 
NAngleBins  = 2.^(1:NDistanceBins); 

%Create checkerboard image 
r    = 1:ImgRows; 
c    = 1:ImgCols; 
[cc,rr]   = meshgrid(c,r); 
Img    = (-1).^(round(rr/3) + round(cc/3)); 
Img(Img<0)  = 0; 

%  [RadialBins,AngularBins] = RadialGrid(ImgRows,ImgCols, ImgRows/2,ImgCols/2, 50,200, 2.^(1:NDistanceBins),NDistanceBins); 
%  figure; 
%  subplot(2,2,1); imagesc(RadialBins); axis equal; axis tight; title('Radial bins'); 
%  subplot(2,2,2); imagesc(AngularBins); axis equal; axis tight; title('Angular bins'); 
% 
%  [RadialBins,AngularBins] = RadialGrid(ImgRows,ImgCols, ImgRows/2,ImgCols/2, 50,200, (1:NDistanceBins)+1,NDistanceBins); 
%  subplot(2,2,3); imagesc(RadialBins); axis equal; axis tight; title('Radial bins'); 
%  subplot(2,2,4); imagesc(AngularBins); axis equal; axis tight; title('Angular bins'); 
%  colormap(jet(255)); 

[RadialBins,AngularBins] = RadialGrid(ImgRows,ImgCols, ImgRows/2,ImgCols/2, 50,200, NAngleBins,NDistanceBins); 

% show the cartoon ;o) 
figure; 
subplot(2,2,1); imagesc(RadialBins); axis equal; axis tight; title('Radial bins'); 
subplot(2,2,2); imagesc(AngularBins); axis equal; axis tight; title('Angular bins'); 
subplot(2,2,3); imagesc(Img);   axis equal; axis tight; title('Original image'); 
subplot(2,2,4); imagesc(Img);   axis equal; axis tight; title('Selection image'); 
%return; 

for ir=1:NDistanceBins 
    % compute the radiaal mask 
    rMask  = RadialBins==ir; 

    for ia=1:NAngleBins(ir) 
     % compute the angular mask 
     aMask  = AngularBins==ia; 

     % do some stuff with the images 
     tR    = zeros(ImgRows,ImgCols); 
     tG    = zeros(ImgRows,ImgCols); 
     tB    = zeros(ImgRows,ImgCols); 

     SectorMask  = rMask&aMask; 

     tR(rMask)  = Img(rMask); 
     tG(SectorMask) = Img(SectorMask); 
     tB(aMask)  = Img(aMask); 
     tImg   = cat(3,tR,tG,tB); 

     % and display the results 
     subplot(2,2,4); imagesc(tImg); axis equal; axis tight; 
     title({ 
      sprintf('Radial bin %d of %d;',ir,NDistanceBins) 
      sprintf('Angular bin %d of %d;',ia,NAngleBins(ir)) 
      }) 
     drawnow; 
    end 
end