Article ID: 39368
Article Last Modified on 11/21/2006
APPLIES TO
- Microsoft QuickBasic 4.0
- Microsoft QuickBASIC 4.0b
- Microsoft QuickBasic 4.5 for MS-DOS
- Microsoft BASIC Professional Development System 7.0
- Microsoft BASIC Professional Development System 7.1
- Microsoft BASIC Compiler 6.0
- Microsoft BASIC Compiler 6.0b
This article was previously published under Q39368
SUMMARY
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.
MORE INFORMATION
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
Additional query words: QuickBas BasicCom
Keywords: KB39368
