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Find the distance from camera to vanishing point in matlab

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I have this program that finds the vanishing point for a given set of images. Is there a way to find the distance from the camera and the vanishing point?

Also once the vanishing point is found out, I manually need to find the X and Y coordinates using the tool provided in matlab. How can i code a snippet that writes all the X and Y coordinates into a text or excel file?

Also is there a better and simpler way to find the vanishing point in matlab?

Matlab Calling Function to find Vanishing Point:

clear all; close all;
dname = 'Height';
files = dir(dname);
files(1) = [];
files(1) = [];
for i=1:size(files, 1)
    original = imread(fullfile(dname, files(i).name));
    original = imresize(original,0.35);    
    im = im2double(rgb2gray(original)); 
    [row, col] = findVanishingPoint(im);
    imshow(original);hold;plot(col,row,'rx');
    saveas(gcf,strcat('Height_Result',num2str(i)),'jpg');
    close
end

The findVanishingPoint function:

function [row, col] = findVanishingPoint(im)

DEBUG = 0;

IM = fft2(im);
ROWS = size(IM,1); COLS = size(IM,2);


PERIOD = 2^floor(log2(COLS)-5)+2;
SIZE = floor(10*PERIOD/pi);  
SIGMA = SIZE/9; 
NORIENT = 72; 
E = 8;  
[C, S] = createGaborBank(SIZE, PERIOD, SIGMA, NORIENT, ROWS, COLS, E);


D = ones(ROWS, COLS); 
AMAX = ifftshift(real(ifft2(C{1}.*IM)).^2+real(ifft2(S{1}.*IM))).^2; 
for n=2:NORIENT
    A = ifftshift(real(ifft2(C{n}.*IM)).^2+real(ifft2(S{n}.*IM))).^2;
    D(find(A > AMAX)) = n;        
    AMAX = max(A, AMAX);        
    if (DEBUG==1)
        colormap('hot');subplot(131);imagesc(real(A));subplot(132);imagesc(real(AMAX));colorbar;
        subplot(133);imagesc(D);
        pause
end
end

if (DEBUG==2)
figure('DoubleBuffer','on');
end
T = mean(AMAX(:))-3*std(AMAX(:));
VOTE = zeros(ROWS, COLS);
for row=round(1+SIZE/2):round(ROWS-SIZE/2) 
    for col=round(1+SIZE/2):round(COLS-SIZE/2)
        if (AMAX(row,col) > T)
            indices = lineBresenham(ROWS, COLS, col, row, D(row, col)*pi/NORIENT-pi/2);
            VOTE(indices) = VOTE(indices)+AMAX(row,col);
        end
    end
    if (DEBUG==2)
        colormap('hot');imagesc(VOTE);pause;                                        
end
end
if (DEBUG==2)
close
end

M=1;
[b index] = sort(-VOTE(:));
col = floor((index(1:M)-1) / ROWS)+1;
row = mod(index(1:M)-1, ROWS)+1;
col = round(mean(col));
row = round(mean(row));

The creatGaborBank function:

function [C, S] = createGaborBank(SIZE, PERIOD, SIGMA, NORIENT, ROWS, COLS, E)

if (length(NORIENT)==1)
    orientations=[1:NORIENT];
else
    orientations = NORIENT;
    NORIENT = max(orientations);
end

for n=orientations
    [C{n}, S{n}] = gabormask(SIZE, SIGMA, PERIOD, n*pi/NORIENT);
    C{n} = fft2(padWithZeros(C{n}, ROWS, COLS)); 
    S{n} = fft2(padWithZeros(S{n}, ROWS, COLS));
end

The gabormask function:

function [cmask, smask] = gabormask(Size, sigma, period, orient, E)
if nargin < 5; E = 8; end;
if nargin < 4; orient = 0; end;
if nargin < 3; period = []; end;
if nargin < 2; sigma = []; end;
if nargin < 1; Size = []; end;

if isempty(period) & isempty(sigma); sigma = 5; end;
if isempty(period); period = sigma*2*sqrt(2); end;
if isempty(sigma); sigma = period/(2*sqrt(2)); end;
if isempty(Size); Size = 2*round(2.575*sigma) + 1; end; 

if length(Size) == 1
    sx = Size-1; sy = sx;
elseif all(size(Size) == [1 2])
    sy = Size(1)-1; sx = Size(2)-1;
else
    error('Size must be scalar or 1-by-2 vector');
end;

hy = sy/2; hx = sx/2;
[x, y] = meshgrid(-hx:sx-hx, -hy:sy-hy);

omega = 2*pi/period;
cs = omega * cos(orient);
sn = omega * sin(orient);
k = -1/(E*sigma*sigma);

g = exp(k * (E*x.*x + y.*y));   
xp = x * cs + y * sn;           
cx = cos(xp);                   
cmask = g .* cx;               
sx = sin(xp);                  
smask = g .* sx;               

cmask = cmask - mean(cmask(:));
cmask = cmask/sum(abs(cmask(:)));
smask = smask - mean(smask(:));
smask = smask/sum(abs(smask(:)));

The padWithZeros function:

function out = padWithZeros(in, ROWS, COLS)
out = padarray(in,[floor((ROWS-size(in,1))/2) floor((COLS-size(in,2))/2)],0,'both');
if size(out,1) == ROWS-1
    out = padarray(out,[1 0],0,'pre');
end
if size(out,2) == COLS-1
    out = padarray(out,[0 1],0,'pre');
end

The findHorizonEdge function:

function row = findHorizon(im)
DEBUG = 2;

ROWS = size(im,1); COLS = size(im,2);
e = edge(im,'sobel', [], 'horizontal');
dd = sum(e, 2);
N=3;
row = 1; 
M = 0;
for i=1+N:length(dd)-N
    m = sum(dd(i-N:i+N));    
    if (m > M)
        M = m;
        row = i;
    end
end
imshow(e);pause

The findHorizon function:

function row = findHorizon(im)
DEBUG = 2;

IM = fft2(im);
ROWS = size(IM,1); COLS = size(IM,2);

PERIOD = 2^floor(log2(COLS)-5)+2; 
SIZE = floor(10*PERIOD/pi);  
SIGMA = SIZE/9; 
NORIENT = 72; 
E = 16; 
orientations = [NORIENT/2-10:NORIENT/2+10]; 

[C, S] = createGaborBank(SIZE, PERIOD, SIGMA, orientations, ROWS, COLS, E);

ASUM = zeros(ROWS, COLS);
for n=orientations
    A = ifftshift(real(ifft2(C{n}.*IM)).^2+real(ifft2(S{n}.*IM))).^2;
    ASUM = ASUM + A;        
    if (DEBUG==1)
        colormap('hot');subplot(131);imagesc(real(A));subplot(132);imagesc(real(AMAX));colorbar;
        pause
end
end

ASUM(1:round(1+SIZE/2), :)=0; ASUM(end-round(SIZE/2):end, :)=0;
ASUM(:,end-round(SIZE/2):end)=0; ASUM(:, 1:1+round(SIZE/2))=0;
dd = sum(ASUM, 2);
[temp, row] = sort(-dd);
row = round(mean(row(1:10)));
if (DEBUG == 2)
    imagesc(ASUM);hold on;line([1:COLS],repmat(row,COLS));
    pause
end

The lineImage function:

function v = lineimage(x0, y0, angle, s) 

if (abs(tan(angle)) > 1e015)
    a(1,:) = repmat(x0,s(1),1)';
    a(2,:) = [1:s(1)];
elseif (abs(tan(angle)) < 1e-015)
    a(2,:) = repmat(y0,s(2),1)';
    a(1,:) = [1:s(2)];
else

    k = tan(angle);
    hiX = round((1-(s(1)-y0+1)+k*x0)/k);
    loX = round((s(1)-(s(1)-y0+1)+k*x0)/k);
    temp = max(loX, hiX);
    loX = max(min(loX, hiX), 1);
    hiX = min(s(2),temp);
    a(1,:) = [loX:hiX];
    a(2,:) = max(1, floor(s(1)-(k*a(1,:)+(s(1)-y0+1)-k*x0)));
end
v = (a(1,:)-1).*s(1)+a(2,:);

The lineVector function:

function [abscissa, ordinate] = linevector(x0, y0, angle, s) 

if (rad2deg(angle) == 90) 
        abscissa = repmat(x0,s(1),1);
        ordinate = [1:s(1)];
else
    k = tan(angle);
    hiX = round((1-(s(1)-y0+1)+k*x0)/k);
    loX = round((s(1)-(s(1)-y0+1)+k*x0)/k);
    temp = max(loX, hiX);
    loX = max(min(loX, hiX), 1);
    hiX = min(s(2),temp);

    abscissa = [loX:hiX];
    ordinate = k*abscissa+((s(1)-y0+1)-k*x0);
end

The lineBresenham function:

function [i] = lineBresenham(H,W,Sx,Sy,angle)

k = tan(angle);
if (angle == pi || angle == 0)
    Ex = W;
    Ey = Sy;
    Sx = 1;
elseif (angle == pi/2)
    Ey = 1;
    i = (Sx-1)*H+[Ey:Sy];
    return;
elseif k>0 & k < (Sy-1)/(W-Sx) 
    Ex = W;
    Ey = round(Sy-tan(angle)*(Ex-Sx));
elseif k < 0 & abs(k) < (Sy-1)/(Sx-1) 
    Ex = 1;
    Ey = round(Sy-tan(angle)*(Ex-Sx));
else
    Ey = 1;   
    Ex = round((Sy-1)/tan(angle)+Sx);
end
Dx = Ex - Sx;
Dy = Ey - Sy;
iCoords=1;
if(abs(Dy) <= abs(Dx))
    if(Ex >= Sx)
        D = 2*Dy + Dx;
        IncH = 2*Dy;
        IncD = 2*(Dy + Dx);
        X = Sx;
        Y = Sy;
        i(iCoords) = (Sx-1)*H+Sy;
        iCoords = iCoords + 1;
        while(X < Ex)
            if(D >= 0)
                D = D + IncH;
                X = X + 1;
            else
                D = D + IncD;
                X = X + 1;
                Y = Y - 1;
            end
            i(iCoords) = (X-1)*H+Y;
            iCoords = iCoords + 1;                
        end
    else 
        D = -2*Dy + Dx;
        IncH = -2*Dy;
        IncD = 2*(-Dy + Dx);
        X = Sx;
        Y = Sy;
        i(iCoords) = (Sx-1)*H+Sy;
        iCoords = iCoords + 1;
        while(X > Ex)
            if(D <= 0)
                D = D + IncH;
                X = X - 1;
            else
                D = D + IncD;
                X = X - 1;
                Y = Y - 1;
            end
            i(iCoords) = (X-1)*H+Y;
            iCoords = iCoords + 1;   
        end
    end


else 
    Tmp = Ex;
    Ex = Ey;
    Ey = Tmp;
    Tmp = Sx;
    Sx = Sy;
    Sy = Tmp;
    Dx = Ex - Sx;
    Dy = Ey - Sy;
    if(Ex >= Sx)
        D = 2*Dy + Dx;
        IncH = 2*Dy;
        IncD = 2*(Dy + Dx);
        X = Sx;
        Y = Sy;
        i(iCoords) = (Sy-1)*H+Sx;
        iCoords = iCoords + 1;
        while(X < Ex)
            if(D >= 0)
                D = D + IncH;
                X = X + 1;
            else
                D = D + IncD;
                X = X + 1;
                Y = Y - 1;
            end
            i(iCoords) = (Y-1)*H+X;
            iCoords = iCoords + 1;   
        end
    else
        D = -2*Dy + Dx;
        IncH = -2*Dy;
        IncD = 2*(-Dy + Dx);
        X = Sx;
        Y = Sy;
        i(iCoords) = (Sy-1)*H+Sx;
        iCoords = iCoords + 1;
        while(X > Ex)
            if(D <= 0)
                D = D + IncH;
                X = X - 1;
            else
                D = D + IncD;
                X = X - 1;
                Y = Y - 1;
            end
            i(iCoords) = (Y-1)*H+X;
            iCoords = iCoords + 1;   
        end
    end        
end
image matlab image-processing coordinates vanishing-point
Original Q&A
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There are 1 answers

5
denahiro On

  1. The vanishing point is at infinity hence the distance to the camera is of no use.

  2. Use xlswrite or dlmwrite to write into excel or text file respectively.

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