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Q39368: QuickBASIC Program to Rotate Characters and Graphic Images

Article: Q39368
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom SR# S881213-23 | mspl13_basic
Last Modified: 4-SEP-1990

The subprogram below rotates two-dimensional graphic images. It takes
as parameters the upper-left and lower-right corners of the region to
rotate, and the number of degrees to rotate the picture.

It also includes a subprogram that returns the upper-left corner of an
ASCII-printed character for those who wish to rotate individual
characters on the screen.

This information applies to Microsoft QuickBASIC versions 4.00, 4.00b,
and 4.50; to Microsoft BASIC Compiler versions 6.00 and 6.00b for
MS-DOS; and to Microsoft BASIC Professional Development System (PDS)
versions 7.00 and 7.10 for MS-DOS and MS OS/2.

The character rotation will perform correctly only if the coordinate
system is not altered (such as with the WINDOW statement).

To rotate larger areas, compile with /ah.

The program works correctly on screen modes 1, 2, 3 (Hercules), 7, 8,
and 9. It can be expanded to support modes 10, 11, and 12 by changing
the FindCharPos routine to include those screens.

The more complex the image, the slower the program will run.

The following is a code example:

' This program is provided as is. No guarantees about performance
' or support are implied.
DECLARE SUB FindCharPos (row%, col%, gx%, gy%, screenmode%)
DECLARE SUB RotatePic (ulx%, uly%, lrx%, lry%, deg!)
DECLARE SUB RotatePoint (p!(), deg!)
DECLARE SUB TranslatePoint (p!(), xdist!, ydist!)
DECLARE SUB MatrixMult (p!(), t!())

CLS
INPUT "Enter Screen Mode (1, 2, 3, 7, 8, or 9) : ", screenmode%
INPUT "Enter a Rotation (in Degrees) : ", r

SCREEN screenmode%

'** Rotating a Portion of a Picture **
FOR row = 10 TO 150 STEP 10
  LINE (10, row)-(150, row)
NEXT row
CALL RotatePic(55, 55, 100, 100, r)
LOCATE 20
INPUT "Press Enter to Continue", k$

'** Rotating a Character **
CLS
textRow% = 10
textCol% = 5
LOCATE textRow%, textCol%
PRINT "H"
CALL FindCharPos(textRow%, textCol%, gx%, gy%, screenmode%)

IF screenmode% = 3 OR screenmode% = 9 THEN  'Characters are 8x14
  CALL RotatePic(gx%, gy%, gx% + 8, gy% + 14, r)
ELSE                                        'Characters are 8x8
  CALL RotatePic(gx%, gy%, gx% + 8, gy% + 8, r)
END IF

LOCATE 20
INPUT "Press Enter ", k$

SCREEN 0    '* Restore Screen *

' * ----------------------------------------------------------- *

SUB FindCharPos (row%, col%, gx%, gy%, screenmode%)
'* Translates character coordinates to graphics coordinates. *
'* Returns the upper left corner of the character box.       *

  SELECT CASE screenmode%
    CASE 1 TO 2
      gx% = col% * 8 - 9
      gy% = row% * 8 - 9
    CASE 3             ' * Hercules *
      gx% = col% * 8 + 1
      gy% = row% * 14 - 14
    CASE 7 TO 8
      gx% = col% * 8 - 9
      gy% = row% * 8 - 9
    CASE 9
      gx% = col% * 8 - 8
      gy% = row% * 14 - 14
    CASE ELSE
      PRINT "Error in Screen Mode Setting - FindCharPos"
  END SELECT
END SUB

SUB MatrixMult (p!(), t!())
'* Multiply 1x4 array with a 4x4 array *

  DIM r(1 TO 3) AS SINGLE

  FOR i = 1 TO 3
    r(i) = (p!(1) * t!(1,i)) + (p!(2) * t!(2,i)) + (p!(3) * t!(3,i))
  NEXT i
  FOR i = 1 TO 3
    p!(i) = r(i)
  NEXT i
END SUB

SUB RotatePic (ulx%, uly%, lrx%, lry%, deg!)
' * This Program will scan any picture and replace it    *
' * with a rotated version in the current foreground and *
' * background colors.                                   *
' * To rotate larger pictures, compile with /ah.         *

  REM $DYNAMIC
  DIM p(1 TO 3) AS SINGLE

  xspan = lrx% - ulx%
  yspan = lry% - uly%
  IF FRE(-1) < (xspan * yspan * 2 * 2) THEN  '* Enough memory? *
    PRINT "Area too large to rotate"
    EXIT SUB
  ELSE
    DIM rotArea(1 TO xspan, 1 TO yspan, 1 TO 2) AS INTEGER
  END IF

  FOR i = 0 TO xspan - 1
    FOR j = 0 TO yspan - 1
      IF POINT(i + ulx%, j + uly%) <> 0 THEN
        PSET (i + ulx%, j + uly%), 0
        p(1) = i + ulx%
        p(2) = j + uly%
        p(3) = 1
        CALL TranslatePoint(p(), CSNG(-ulx%) - (xspan / 2),_
                                 CSNG(-uly%) - (yspan / 2))
        CALL RotatePoint(p(), deg!)
        CALL TranslatePoint(p(), CSNG(ulx%) + (xspan / 2),_
                                 CSNG(uly%) + (yspan / 2))
        rotArea(i + 1, j + 1, 1) = p(1)
        rotArea(i + 1, j + 1, 2) = p(2)
      END IF
    NEXT j
  NEXT i

  FOR i = 1 TO xspan
    FOR j = 1 TO yspan
      PSET (rotArea(i, j, 1), rotArea(i, j, 2))
    NEXT j
  NEXT i
END SUB

REM $STATIC
SUB RotatePoint (p!(), deg!)
'* Set up the rotation matrix and multiply with the point. *

  CONST PI = 3.14159

  DIM RotMatrix(1 TO 3, 1 TO 3) AS SINGLE

  radians! = deg! * PI / 180

  RotMatrix(1, 1) = COS(radians!)
  RotMatrix(1, 2) = SIN(radians!)
  RotMatrix(2, 1) = -SIN(radians!)
  RotMatrix(2, 2) = COS(radians!)
  RotMatrix(3, 3) = 1

  CALL MatrixMult(p!(), RotMatrix())
END SUB

SUB TranslatePoint (p!(), xdist!, ydist!)
'* Set up the translation matrix and multiply with the point. *

  DIM t(1 TO 3, 1 TO 3) AS SINGLE

  t(1, 1) = 1
  t(2, 2) = 1
  t(3, 3) = 1
  t(3, 1) = xdist!
  t(3, 2) = ydist!

  CALL MatrixMult(p!(), t())
END SUB

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