Draw Regular Shapes: Circles, Rectangles, and Ovals

Circle() draws a circle with the center point and radius given. Subsequent arguments specify additional radii.

win = New Window( "Circles",

Graph Box( Frame Size( 200, 200 ),

Circle( {50, 50}, 10, 12, 25 )

Circle() also has a final optional argument, "fill". This string indicates that all circles defined in the function are filled with the current fill color. If "fill" is omitted, the circle is empty.

图 12.15 Drawing Circles

Note that a circle is always a circle, even if you resize the graph to a different aspect ratio. If you want your circle to change aspect ratios (in other words, cease being a circle) when the graph is resized, use an oval instead.

If you do not want your circle to resize if the graph is resized, specify the radius in pixels instead:

win = New Window( "Circles",

Graph Box(

Frame Size( 200, 200 ),

Circle( {50, 50}, Pixel Radius( 10 ), Pixel Radius( 12 ), Pixel Radius( 25 ) )

)

);

Rectangles

Rect() draws a rectangle from the diagonal coordinates you specify. The coordinates can be specified either as four arguments in order (left, top, right, bottom), or as a pair of lists ({left, top}, {right, bottom}).

win = New Window( "Rectangles",

Graph Box(

Frame Size( 200, 200 ),

Pen Color( 1 );

Rect( 0, 40, 60, 0 );

Pen Color( 3 );

Rect( 10, 60, 70, 10 );

Pen Color( 4 );

Rect( 50, 90, 90, 50 );

Pen Color( 5 );

Rect( 0, 80, 70, 70 );

)

);

Rect() has an optional fifth argument, fill. Specify 0 to get an unfilled rectangle and 1 to get a filled rectangle. The default value for fill is 0. The rectangle is filled with the current fill color.

Any negative fill argument produces an unfilled frame inset by one pixel:

win = New Window( "Framed Rectangle",

Graph Box( Frame Size( 200, 200 ), Rect( 0, 40, 60, 0, -1 ) )

);

Ovals

Oval() draws an oval inside the rectangle given by its x1, y1, x2, and y2 arguments:

win = New Window( "Ovals",

Graph Box(

Frame Size( 200, 200 ),

Pen Color( 1 );

Oval( 0, 40, 60, 0 );

Pen Color( 3 );

Oval( 10, 60, 70, 10 );

Pen Color( 4 );

Oval( 50, 90, 90, 50 );

Pen Color( 5 );

Oval( 0, 80, 70, 70 );

)

);

Oval() also has an optional fifth argument, fill. Specify 0 to get an unfilled rectangle and 1 to get a filled oval. The default value for fill is 0. The oval is filled with the current fill color.

图 12.16 shows rectangles and ovals, drawn both filled and unfilled. Notice that filled rectangles do not have outlines. Ovals do have outlines. If you want a filled rectangle with an outline, you must draw the filled rectangle and then draw an unfilled rectangle with the same coordinates.

图 12.16 Rectangles and Ovals, Unfilled and Filled