168 Part III: Advanced Programming with Liberty BASIC
NOMAINWIN
WindowHeight = 300
WindowWidth = 250
OPEN “Graphics window” FOR Graphics AS #main
PRINT #main, “HOME; DOWN; NORTH”
PRINT #main, “COLOR green”
PRINT #main, “GO 35; TURN 90; UP; GO 35; TURN 90”
PRINT #main, “COLOR pink”
PRINT #main, “DOWN; go 35”
PRINT #main, “FLUSH”
PRINT #main, “trapclose [quit]”
WAIT
[quit]
CONFIRM “Are you sure you want to quit?”; quit$ IF quit$ = “no” THEN WAIT
CLOSE #main END
Drawing Circles
Because drawing individual lines can become tiresome, you may want to tell Liberty BASIC to draw circles instead. To draw a circle, you can use the CIRCLE command as in the following example:
PRINT #Windowhandle, “CIRCLE R”
Here’s what’s happening in this example:
1.The #Windowhandle portion defines the graphics window in which the circle that turtle graphics draws appears.
2.The CIRCLE R command tells the computer to draw a circle, at the current position of the turtle (pen), with a radius that R defines, where R is a number such as 35 or 90.
If you want to draw your circle in a specific color, you can use the COLOR command prior to the CIRCLE command, as follows:
PRINT #Windowhandle, “COLOR darkpink; CIRCLE R”
Chapter 12: Drawing Pictures and Making Noise 169
You can also fill in your circle with a specific color by using the BACKCOLOR command prior to using the CIRCLEFILLED command, as follows:
PRINT #Windowhandle, “BACKCOLOR yellow; CIRCLEFILLED R”
To see how turtle graphics can create circles, try the following program, which draws two circles, as shown in Figure 12-2:
Figure 12-2:
Drawing two circles using turtle graphics.
NOMAINWIN
WindowHeight = 300
WindowWidth = 250
OPEN “Graphics window” FOR Graphics AS #main
PRINT #main, “HOME; DOWN”
PRINT #main, “COLOR red; CIRCLE 40” PRINT #main, “PLACE 45 50”
PRINT #main, “COLOR darkblue; BACKCOLOR yellow; CIRCLEFILLED 40”
PRINT #main, “FLUSH”
PRINT #main, “trapclose [quit]”
WAIT
[quit]
CONFIRM “Are you sure you want to quit?”; quit$ IF quit$ = “no” THEN WAIT
CLOSE #main END
170 Part III: Advanced Programming with Liberty BASIC
The seventh line in the preceding program uses the PLACE command, which moves the turtle (pen) position without drawing a line.
Drawing Boxes
Just as you can draw circles, Liberty BASIC also enables you to draw boxes.
To draw a box, you can use the BOX command as in the following example:
PRINT #Windowhandle, “BOX x y”
Here’s what’s happening in this example:
1.The #Windowhandle portion defines the graphics window where turtle graphics draws the box.
2.The BOX x y command tells the computer to draw a box where the current turtle (pen) position defines one corner of the box and the x and y coordinates define the location of the opposite corner.
If you want to draw your circle in a specific color, you can use the COLOR command prior to the BOX command, as follows:
PRINT #Windowhandle, “COLOR red; BOX x y”
You can also fill in your circle with a specific color by using the BACKCOLOR command prior to using the BOXFILLED command, as in the following example:
PRINT #Windowhandle, “BACKCOLOR pink; BOXFILLED x y”
To see how turtle graphics can create boxes, try the following program, which draws two boxes.
NOMAINWIN
WindowHeight = 300
WindowWidth = 250
OPEN “Graphics window” FOR Graphics AS #main
PRINT #main, “HOME; DOWN”
PRINT #main, “COLOR red; BOX 190 190” PRINT #main, “PLACE 45 50”
PRINT #main, “COLOR darkblue; BACKCOLOR pink; BOXFILLED 80 80”
Chapter 12: Drawing Pictures and Making Noise 171
PRINT #main, “FLUSH”
PRINT #main, “trapclose [quit]”
WAIT
[quit]
CONFIRM “Are you sure you want to quit?”; quit$ IF quit$ = “no” THEN WAIT
CLOSE #main END
Displaying Text
Besides drawing lines, circles, and boxes, you can also create text in a graphics window. To display text in a graphics control, you just need to move the turtle (pen) to the location where you want the text to appear and then print the text with a backslash in front, which the following program accomplishes:
NOMAINWIN
WindowHeight = 300
WindowWidth = 250
OPEN “Text graphics window” FOR Graphics AS #main
PRINT #main, “HOME”
PRINT #main, “\This is an”
PRINT #main, “\example of text”
PRINT #main, “FLUSH”
PRINT #main, “trapclose [quit]”
WAIT
[quit]
CONFIRM “Are you sure you want to quit?”; quit$ IF quit$ = “no” THEN WAIT
CLOSE #main END
The backslash character (\) displays the text and causes a new line to print, as shown in Figure 12-3. That way, you can display multiple lines of text without needing to move the turtle (pen) each time.
For variety, you can add color to your text or to the background. To change the color of your text, use the COLOR command, as follows: