Faster way to draw bounding box around object in an image?

Hi everyone,

I am new to Matlab and this is my first attempt at image processing. I want to count the number of boats in a large collection of images like this:

The code I used to draw this box is quite simple:

rgbImage=imread('scene00074.png');
imshow(rgbImage);
hold on
rectangle('Position', [960, 490, 125, 40],...  %right, top, width, height
'EdgeColor','r','LineWidth',3)

I did this by trial and error, changing the numbers until I got the box in the right spot. I need to do this with a lot of images and then I plan eventually to use google vision to analyse my photos... is there a faster way, maybe using an interface, to select where the box goes? Prior to giving me the bounding box vertices?

Also, right now I have the pixel vertices but how would I get the vertices from 0-1?

Thanks!

[KSSV]

If you are talking about drawing rectangles manually; read about imrect.