# 如何从投影图中准确获取线段？How to accurately acquire line segments from the projection plot?

``````%complementing as text must be non zero and background should be 0
img_comp = imcomplement(img);

%calculate the horizontal projections and plot it to verify the threshold
horizontal_projections = sum(img_comp, 2);
plot(horizontal_projections)

%A very crude method of automatically detecting the threshold

proj_mean = mean(horizontal_projections);
lines = horizontal_projections > floor(proj_mean);

% Find Rising and falling edges
d = diff(lines);
startingColumns = find(d>0);
endingColumns = find(d<0);

% Extract each line and save it in a cell
for lines_k = 1 : length(startingColumns)
lines_extracted{lines_k} = img(startingColumns(lines_k):endingColumns(lines_k), :);
end
``````

## 2 个回复2

### ===============>>#1 票数：1 已采纳

``````img = im2double(imread('StackOverflow-Example.jpg'));
rp = img(:, :, 1) / 255 ;
bp = img(:, :, 2) / 255 ;
gp = img(:, :, 3) / 255 ;
kb = 0.114;
kr = 0.299;
y = kr * rp + (1 - kr - kb) * gp + kb * bp;
y = max(max(y))-y;
y = y ./ y;
surf(y,'EdgeColor','none','LineStyle','none')
view(0, -90)
``````

``````%% Load image and find intensity %%
img = im2double(imread('test.jpg')); % load image and convert to doubles to allow for calculations
rp = img(:, :, 1) / 255 ; % normalized red portion
bp = img(:, :, 2) / 255 ; % normalized blue portion
gp = img(:, :, 3) / 255 ; % normalized green portion
kb = 0.114; % blue constant from Wikipedia
kr = 0.299; % red constant from Wikipedia
x = kr * rp + (1 - kr - kb) * gp + kb * bp; % normalized intensity in image
x = max(max(x))-x; % removed background

y = x ./ x; % everything left is high

z = y;
z(isnan(y)) = 0; % turn nan's to zero
divisions = find(sum(z,2) > 5); % find all lines that have less than 5 pixels
divisions = [divisions(1); divisions(diff(divisions) > 10); size(z, 1)]; % find the line breaks

rows = cell(length(divisions), 1);

for i = 1:numel(rows)-1
line = z(divisions(i):divisions(i+1), :); % grab line
j = divisions(i) + find(sum(line,2) > 5) - 1; % remove the white space
line = y(j, :);
rows{i} = line; %store the line
end

rows(numel(rows)) = [];

%% plot each line %%
for i = 1:numel(rows) ;
figure(i) ;
surf(rows{i},'EdgeColor','none','LineStyle','none');
view(0, -90) ;
end

%% plot entire page %%
figure(numel(rows) + 1)
surf(y,'EdgeColor','none','LineStyle','none') % plot of entire image
view(0, -90)
``````

``````img = im2double(imread('test.jpg'));
rp = img(:, :, 1) / 255 ;
bp = img(:, :, 2) / 255 ;
gp = img(:, :, 3) / 255 ;
kb = 0.114;
kr = 0.299;
x = kr * rp + (1 - kr - kb) * gp + kb * bp;
x = max(max(x))-x;
xp = x;
xp(xp == min(min(xp))) = nan;

y = x ./ x;

z = y;
z(isnan(y)) = 0;
divisions = find(sum(z,2) > 5);
divisions = [divisions(1); divisions(diff(divisions) > 10); size(z, 1)];

rows = cell(length(divisions) - 1, 1);

for i = 1:numel(rows)
line = z(divisions(i):divisions(i+1), :);
j = divisions(i) + find(sum(line,2) > 5) - 1;
line = xp(j, :);
rows{i} = line;

figure(i) ;
surf(rows{i},'EdgeColor','none','LineStyle','none');
axis('equal')
view(0, -90) ;
end

figure(numel(rows) + 1)
surf(xp,'EdgeColor','none','LineStyle','none')
axis('equal')
view(0, -90)
``````

``````%Turn warning message off

%Read in image in int8

%Convert to double
img = im2double(originalImg);

%Take R, G, & B components
rp = img(:, :, 1) ;
gp = img(:, :, 2) ;
bp = img(:, :, 3) ;

%Get intensity
kb = 0.114;
kr = 0.299;
yp = kr * rp + (1 - kr - kb) * gp + kb * bp;

%Flip to opposite of intensity
ypp = max(max(yp))-yp;

%Normalize flipped intensity
z = ypp ./ ypp;
z(isnan(z)) = 0;

%Find lines, this may need to be tuned
MaxPixelsPerLine = 5;
MinRowsPerLine = 10;
divisions = find(sum(z,2) > MaxPixelsPerLine);
divisions = [divisions(1); divisions(diff(divisions) > MinRowsPerLine); size(z, 1)];

%Preallocate for number of lines
colorRows = cell(length(divisions) - 1, 1);

for i = 1:numel(rows)
%Extract the lines in RGB
line = z(divisions(i):divisions(i+1), :);
j = divisions(i) + find(sum(line,2) > 5) - 1;
colorRows{i} = originalImg(j, :, :);

%Print out the line
figure(i) ;
imshow(colorRows{i})
end

%Print out the oringinal image
figure(numel(rows) + 1)
imshow(originalImg)

%Turn the warning back on
``````

### ===============>>#2 票数：1

``````original = imread('o6WEN.jpg');
``````

``````img=rgb2gray(original); .
``````

``````se = strel('rectangle',[30 200]);
``````

`````` img = imtophat(img,se);
``````

``````img = imadjust(img);
``````

se = strel（'line'，20,0）;

``````img = imdilate(img,se);
``````

``````img=im2bw(img,graythresh(img));
``````

`````` stats=regionprops(img,'BoundingBox');
figure, imshow(img)
``````

``````BoundingBoxes=struct2cell(stats);
BoundingBoxes=cell2mat(BoundingBoxes'); % making it into an array
[~,ind]=sort(BoundingBoxes(:,2)); % sorting it to y
BoundingBoxes=BoundingBoxes(ind,:); % apply the sorted vector

lineNr=8;
imshow(original(BoundingBoxes(2,lineNr):BoundingBoxes(2,lineNr)+BoundingBoxes(4,lineNr),BoundingBoxes(1,lineNr):BoundingBoxes(1,lineNr)+BoundingBoxes(3,lineNr)  ))
``````

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