Draw Picts from Basic

By Steven Leach, Chemical Engineer, Santa Clara, CA

Create PICT Files for MacDraw™ using MS Basic

This a solution to a problem that I was having when I was writing a rather complex figure in BASIC and wanted to save my very valuable work, but wouldn’t or couldn’t use the clipboard, or scrapbook. It seemed to me that the names for the BASIC pictures and the PICT file of the scrapbook seemed awful close so I thought why not bypass the scrapbook altogether ? My first step was to get the format for the MacDraw™ files. I located this on Compuserve in Tech Note 27. But beware there appears to be an error in the wording of this document for it states “If your application is going to create or modify information that you want to make available to MacDraw, you will want to create a data file in the PICT format.” The tech note goes on to explain the first 512 byte header, of which the first 4 bytes is supposed to be “DRWG”, or “PICT”, and if the next two bytes are not “MD” then the rest of the header can be zero bytes (chr$(0)). Well I have news for you this just does not work , the MacDraw™ page comes out blank.

However on examining the PICT files created by several programs like SuperPaint, and Cricket Draw I ascertained that the entire 512 byte header should be zeroed. Walah! my file is read properly. Now what about complex pictures that may be stored in your program as several picture strings. Well here we must concatonate them into a single picture string in order to get the file to be read properly, as is done in the short sample program presented in Listing 1.

This program will work with any MS Basic 2.0 or greater, but if you check, the line segments that make up the sine wave are individual objects in MacDraw™. This is fine for some cases but some of the items I wanted to appear as polygons, or grouped objects. The solution is available in the CLR libraries that are provided in MS Basic 3.0. If you wish to have a polygon in the PICT file, simply create one using the libraries. This adjustment is shown in Listing 2 for the sine wave picture that is later labeled as PICT2$. I also set the creator of the file to be MacDraw™.

I’m in heaven; I can save my pictures for all posterity. Wait what happened to my picture it’s the same and yet different. As usual there are some sobering quirks that you need to know about before you start celebrating. These quirks show up in version 1.9, I have not had a chance to use the version 1.95 that is being released now. The quirks are:

1) Any patterns that are used to draw lines are lost, the lines are solid lines in MacDraw.

2) As you guessed there is the usual problem with the fonts that are presented in MacDraw™.

3) Polygons saved to the PICT file as polygons can never be ungrouped, but they have all of the nice properties that polygons have, they can be smoothed and reshaped.

4) If you use an uneven pen , i.e. when the x and y dimensions of the pen are different; MacDraw will even the line out using the largest size. An example of this is given in listing 1&2 where the rectangle is framed with a pen that is (3,1). When you view the MacDraw picture you can see that the rectangle has a 3 pixel wide line on all sides.

Ok we can create MacDraw PICT files, is it possible to go the other way ? You bet. As a matter of fact it’s easy as long as we restrict the MacDraw picture to relatively simple things. This is required because the string variables that are used to store the pictures in BASIC are limited to 32767 characters. A BASIC program that is quite general is shown in listing 3.

This opens up the possibility of drawing anything in MacDraw and then reading it into BASIC and using it as you wish, perhaps a template for a complex user interface screen, or saving the picture as a resource to be used in your compiled program. It is possible to create dialogs with pictures in them to really wow those “C” programmers who consider BASIC a “toy” language.

Fig. 1 Draw PICT created from Basic

{1}
REM LISTING 1
REM THIS PROGRAM IS USABLE IN ALL MICROSOFT BASIC’S 
 VERSION 2.0 OR REM GREATER
REM try to create a macdraw PICT file
REM Tech Note # 27 specifies the PICT file structure 
 that is expected by MacDraw

    DIM Grey%(3)
    RESTORE PatternData
    FOR j% = 0 TO 3 : READ Grey%(j%) : NEXT

    PatternData:
        DATA -21931,-21931,-21931,-21931

REM define some objects that will be used for this       demonstration
REM read in the data that define the rectangle and 
 circle

DIM rect%(3),aCircle%(3)
RESTORE ObjectData
  READ rect%(0)
  READ rect%(1)
  READ rect%(2)
  READ rect%(3)
  READ aCircle%(0)
  READ aCircle%(1)
  READ aCircle%(2)
  READ aCircle%(3)

    ObjectData:
      DATA 10,10,110,150,100,100,200,200
      
     X.Offset = 0        
‘offset to be used in saving the picture in MacDraw
     Y.Offset = 0        
‘ if offsets not zero picture will have an upper 
‘ right corner at the location (X.Offset,Y.Offset)
  
    REM record first picture with pen on 
    PICTURE ON
     CALL SHOWPEN
     CALL PENSIZE(3,1)
     CALL FRAMERECT(VARPTR(rect%(0)))
     CALL PENNORMAL
     CALL PENPAT(VARPTR(Grey%(0)))
     CALL PAINTOVAL(VARPTR(aCircle%(0)))
     CALL PENSIZE(3,3)
     FOR indx% = 0 TO 3 : aCircle%(indx%) = aCircle%(indx%) + 50 : NEXT
         
     CALL FRAMEOVAL(VARPTR(aCircle%(0)))
     CALL PENNORMAL  
     CALL MOVETO  (10,10)
     CALL LINETO (100,200)
         
    PICTURE OFF
    pict1$ = PICTURE$
    
    REM now start the second picture
    PICTURE ON
        CALL MOVETO(100,100)
        FOR indx% = 1 TO 20
            CALL LINE(indx%,10*SIN(indx%))
        NEXT
    PICTURE OFF
    pict2$ = PICTURE$

REM we must now group all of the separate pictures as a REM single picture 
before they can be outputted to TRM the PICT file

    CALL HIDEPEN
    PICTURE ON
        PICTURE (X.Offset,Y.Offset), pict1$
‘use any valid offset you wish
        PICTURE (X.Offset,Y.Offset), pict2$
‘use same offset to get relationship right
    PICTURE OFF
    Pict$ = PICTURE$

    File.Pict$ = FILES$(0,”Name for this Picture ?”)
‘get the name of the file
    IF LEN(File.Pict$) <  5 THEN END
‘if no file name then quit

OPEN File.Pict$ FOR OUTPUT AS #1
FOR indx% = 1 TO 512 
 PRINT  #1,CHR$(0); 
 NEXT    ‘print out the header for the PICT file

PRINT  #1,Pict$;   ‘ Print out the picture to the file
CLOSE #1
NAME File.Pict$ AS File.Pict$,”PICT”     
‘type the file as PICT so can open from inside MacDraw™

{2}
REM This is listing 2 and is usable in MS BASIC 3.0 or greater
REM create a macdraw PICT file
REM Tech Note # 27 specifies the PICT file structure that is expected 
by MacDraw

LIBRARY “MSTools”

    DIM Grey%(3)
    RESTORE PatternData
    FOR j% = 0 TO 3 : READ Grey%(j%) : NEXT

    PatternData:
        DATA -21931,-21931,-21931,-21931

REM define some objects that will be used for this       demonstration
REM read in the data that define the rectangle and 
 circle

DIM rect%(3),aCircle%(3)
RESTORE ObjectData
  READ rect%(0)
  READ rect%(1)
  READ rect%(2)
  READ rect%(3)
  READ aCircle%(0)
  READ aCircle%(1)
  READ aCircle%(2)
  READ aCircle%(3)

    ObjectData:
      DATA 10,10,110,150,100,100,200,200
      
     X.Offset = 0        
‘offset to be used in saving the picture in MacDraw
     Y.Offset = 0        
‘ if offsets are not zero the picture will have an 
 upper right corner at that location
  
    REM record first picture with pen on 
     PICTURE ON
     CALL SHOWPEN
         CALL PENSIZE(3,1)
         CALL FRAMERECT(VARPTR(rect%(0)))
         CALL PENNORMAL
         
         CALL PENPAT(VARPTR(Grey%(0)))
         CALL PAINTOVAL(VARPTR(aCircle%(0)))

        CALL PENSIZE(3,3)
         FOR indx% = 0 TO 3 : aCircle%(indx%) = aCircle%(indx%) + 50 
: NEXT
         
         CALL FRAMEOVAL(VARPTR(aCircle%(0)))
         CALL PENNORMAL
         
         CALL MOVETO  (10,10)
         CALL LINETO (100,200)
         
    PICTURE OFF
    pict1$ = PICTURE$
    
    REM now start the second picture as polygon
    PGon! = 0
    openPGon PGon!
        CALL MOVETO(100,100)
        FOR indx% = 1 TO 20
            CALL LINE(indx%,10*SIN(indx%))
        NEXT
    CLOSEPGon
    
    PICTURE ON
    FramePgon PGon!
    PICTURE OFF
    pict2$ = PICTURE$

REM we must group all of the separate pictures as a 
 single picture
REM before they can be outputted to the MacDraw™ PICT 
 file
    CALL HIDEPEN
    PICTURE ON
        PICTURE (X.Offset,Y.Offset), pict1$
‘use any valid offset you wish
        PICTURE (X.Offset,Y.Offset), pict2$
‘use same offset to get relationship right
    PICTURE OFF
    Pict$ = PICTURE$

    File.Pict$ = FILES$(0,”Name for this Picture ?”)  ‘get the name of 
the file
    IF LEN(File.Pict$) <  5 THEN END
‘if no file name then quit

OPEN File.Pict$ FOR OUTPUT AS #1
FOR indx% = 1 TO 512     
 ‘print out the header for the PICT file
    PRINT  #1,CHR$(0); 
 ‘ note use of ; to prevent chr$(13)
NEXT 
PRINT  #1,Pict$;
‘ Print out the picture to the file
CLOSE #1
NAME File.Pict$ AS File.Pict$,”PICT”
 ‘type the file as PICT so can open  ‘from inside MacDraw™
Setcreate File.Pict$ , “MDRW”

{3}
‘ listing 3  
‘ This small routine reads MacDraw PICT FILES AND 
‘ displays the PICTURE

    
    File.Pict$ = FILES$(1,”PICT”)
 ‘Get the FileName
    IF LEN(File.Pict$) < 5 THEN END
 ‘if no file name then quit

    OPEN File.Pict$ FOR INPUT AS #1
 ‘ open the file for input
    FOR indx% = 1 TO 512   
 ‘read the the first 512 byte header
        tmp$ = INPUT$(1,#1) 
    NEXT       
    PICT$ = INPUT$(LOF(1)-512,#1)    
 ‘ read the rest of the file into a string
    CLOSE #1
 ‘  close the file
    CLS
 ‘ clear the screen and display the picture
    PICTURE , PICT$