Insert Distance Tool into an Image

Insert a Distance tool into an image. Use makeConstrainToRectFcn to specify a drag constraint function that prevents the Distance tool from being dragged outside the extent of the image. Right-click the Distance tool and explore the context menu options.

imshow('pout.tif')
h = imdistline;
fcn = makeConstrainToRectFcn('imline',get(gca,'XLim'),get(gca,'YLim'));
setDragConstraintFcn(h,fcn);   

Position Endpoints of Distance Tool

Position endpoints of the Distance tool at the specified locations.

imshow('pout.tif')
h = imdistline(gca,[10 100],[10 100]);

Delete the Distance tool.

delete(h)

Use Distance Tool with Spatial Referencing

Use the Distance tool with XData and YData of associated image in non-pixel units. This example requires the boston.tif image from the Mapping Toolbox™ software, which includes material copyrighted by GeoEye™, all rights reserved.

start_row = 1478;
end_row = 2246;
meters_per_pixel = 1;
rows = [start_row meters_per_pixel end_row];
start_col = 349;
end_col = 1117;
cols = [start_col meters_per_pixel end_col];
img  = imread('boston.tif','PixelRegion',{rows,cols});
figure
hImg = imshow(img);
title('1 meter per pixel')

Specify the initial position of distance tool on Harvard Bridge.

hline = imdistline(gca,[271 471],[108 650]);
setLabelTextFormatter(hline,'%02.0f meters');

Repeat the process but work with a 2 meter per pixel sampled image. Verify that the same distance is obtained.

meters_per_pixel = 2;
rows = [start_row meters_per_pixel end_row];
cols = [start_col meters_per_pixel end_col];
img  = imread('boston.tif','PixelRegion',{rows,cols});
figure  
hImg = imshow(img);
title('2 meters per pixel')

Convert XData and YData to meters using conversion factor.

XDataInMeters = get(hImg,'XData')*meters_per_pixel; 
YDataInMeters = get(hImg,'YData')*meters_per_pixel;

Set XData and YData of the image to reflect desired units.

set(hImg,'XData',XDataInMeters,'YData',YDataInMeters);    
set(gca,'XLim',XDataInMeters,'YLim',YDataInMeters);

Specify the initial position of distance tool on Harvard Bridge.

hline = imdistline(gca,[271 471],[108 650]);
setLabelTextFormatter(hline,'%02.0f meters');