mjhjmtu

I know that I can draw a rectangle with tikz using draw (0.0,0.0) rectangle (1.0,1.0);. Is there a possibility to determine all 4 edge coordinates directly from the shape?

I do can save the lower left coordinate and the upper right by draw (0.0,0.0) coordinate (lb) rectangle (1.0,1.0) coordinate (ru);. But is there a way to get the upper left and bottom right corner directly from the shape?

I know I can calculate them. But are they directly accessible from the shape?

MWE

documentclassstandalone

usepackagetikz
usetikzlibrarycalc

begindocument

begintikzpicture

% the rectangle
draw (0.0,0.0) coordinate (lb) rectangle (1.0,1.0) coordinate (ru);

% coordinates
draw (lb) circle [radius=2pt];
draw (ru) circle [radius=2pt];

% calculated coordinates
draw[dashed] (lb |- ru) coordinate (lu) circle [radius=2pt];
draw[dashed] (lb -| ru) coordinate (rb) circle [radius=2pt];

endtikzpicture

enddocument

You could define your own rectangle path. In the MWE

documentclass[tikz,border=3.14mm]standalone
begindocument
begintikzpicture[my rectangle/.style=to path= coordinate (#1-4) (tikztostart) coordinate (#1-1) ]
draw (0,0) edge[my rectangle=krtek] (1,1);
foreach X in 1,...,4
draw (krtek-X) circle [radius=2pt];
endtikzpicture
enddocument

the style my rectangle=<coordinate base name> will give the four corners the names coordinate base name-1, ... , coordinate base name-4.

And there are, of course, predefined shapes that have the corner coordinates stored in anchors.

documentclass[tikz,border=3.14mm]standalone
begindocument
usetikzlibraryshapes.geometric
begintikzpicture

% the rectangle
path (0,0) node[draw,anchor=south west,minimum size=1cm] (R) ;
foreach X in 45,135,225,315
draw (R.X) circle [radius=2pt];

path (2,0) node[draw,anchor=south west,minimum size=sqrt(2)*1cm,regular polygon,regular
polygon sides=4] (poly) ;

foreach X in 1,...,4
draw (poly.corner X) circle [radius=2pt];

endtikzpicture

enddocument

If you don't want to explicitely declare coordinates for the corners, you can automatically convert your rectangle into a node with fit library. This way, the resultant node gives you all rectangular anchors without havint to name them.

Following example shows how to insert rectangular coordinates into fit parameter. The result node is equivalent to previously drawn rectangle (you don't need to draw the previous rectangle, it's just for demonstration purposes).

documentclass[tikz,border=2mm]standalone 
usetikzlibraryfit

begindocument
begintikzpicture

draw (0,0) rectangle (2,1);
node[fit=(0,0) (2,1), inner sep=0pt, draw=red, opacity=.5] (a) ;

foreach i in north east, north west, south east, south west
 draw (a.i) circle(2pt);
endtikzpicture
enddocument