MATLAB: Select points inside a polygon

helpMATLABplotplottingpolygon

I have 96 points (longitude and latitude); each point is a center of 0.5 x 0.5 pixel (box), on the other hand, I have a polygon, I want to select each pixel that placed in or on my polygon.
I can do it easily like this scrip below but the problem of this code is it just considers a point (center of the pixel) not an entire pixel to index. 
polygon1_x = polygon1_x.';                                  % x of polygons
polygon1_y = polygon1_y.';                                  % y of polygons
lat = Points.lat;                                         % x of points = lat
lon = Points.lon;                                         % y of points = lon
[in,on] = inpolygon(lat,lon,polygon1_x,polygon1_y);         % Logical Matrix
inon = in | on;                                             % Combine ‘in’ And ‘on’
idx = find(inon(:));                                        % Linear Indices Of ‘inon’ Points
latcoord = lat(idx);                                        % X-Coordinates Of ‘inon’ Points
loncoord = lon(idx);                                        % Y-Coordinates Of ‘inon’ Points
clf
figure(1)
plot(lon, lat, '.')                                        % Plot All Points
hold on
plot(polygon1_y, polygon1_x, '.')                          % Plot Polygon
plot(loncoord, latcoord, 'gp')  
OUTPUT = idx;                                              % the output is idx
So I would be grateful if anyone can told me how I can index the row number of points from Point.mat which placed in/on my shapefile if the points are center of 0.5 x0.5 pixels. In this way, I can effectively select pixels that are in or on my polygon. I need the output like idx.
Thank you so much.

Best Answer

Here is the code using POLYSHAPE
load('Points.mat')
load('polygon1_x.mat')
load('polygon1_y.mat')
lat = Points.lat;                                         % x of points = lat
lon = Points.lon;                                         % y of points = lon
wpixel = 0.5;
hpixel = 0.5;
pixel0 = [-1  1 1 -1;
          -1 -1 1  1]' .* [wpixel, hpixel]/2;
Island = polyshape([polygon1_y(:) polygon1_x(:)]);
for k=1:length(lat)
    poly = polyshape([lon(k) lat(k)]+pixel0);
    Ik = intersect(poly,Island);
    isin = ~isempty(Ik.Vertices);
    pixel(k).poly = poly;
    pixel(k).isin = isin;
end
% Index of pixel that intersect with Island
idxin = find([pixel.isin]) % <=== HERE IS THE INDEX YOU NEED 
% Graphical output
close all
plot(Island)
hold on
for k=1:length(pixel)
    if pixel(k).isin
        color = 'r';
    else
        color = 'w';
    end
    plot(pixel(k).poly, 'FaceColor', color);
end
axis equal
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