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  • Rotating Bitmap Without Window

    I'm new to all this graphic stuff (never needed it til now) and I'm trying to rotate a bitmap without displaying it on a window...
    The code below doesn't work because the bitblt is looking for a device context and I'm giving it a bitmap handle, but I'm not sure how to duplicate bitblt without a window. Any ideas???

    Also, how do you save a handle of a memory bitmap to a disk file?

    Code:
    function rotatedrawing(byval namefile$,byval ldegrees&)
    
         ff&=freefile
         open namefile$ for binary as #ff& base=0
         seek #ff&,18
         get$ #ff&,8,b$
         close #ff&
    
         lwidth&=cvl(left$(b$,4))
         lheight&=cvl(right$(b$,4))
         graphic bitmap load namefile$,lwidth&,lheight& to hbmp&
    
         'compute the radians from the input degrees
         lradians&=(3.14159)*ldegrees&/180
    
         ' compute the sine/cosinse of the radians used to
         ' rotate this image
         lsine&=sin(lradians&)
         lcosine&=cos(lradians&)
    
         ' compute the size of the new bitmap being created
         x1&=-lheight&*lsine&
         y1&=lheight&*lcosine&
         x2&=lwidth&*lcosine&-lheight&*lsine&
         y2&=lheight&*lcosine&+lwidth&*lsine&
         x3&=lwidth&*lcosine&
         y3&=lwidth&*lsine&
    
         ' figure out the max/min size of the new bitmap
         lminx&=min(0,min(x1&,min(x2&,x3&)))
         lminy&=min(0,min(y1&,min(y2&,y3&)))
         lmaxx&=max(x1&,max(x2&,x3&))
         lmaxy&=max(y1&,max(y2&,y3&))
    
         ' set the new bitmap width/height
         lnewwidth&=lmaxx&-lminx&
         lnewheight&=lmaxy&-lminy&
    
         ''create a new bitmap based upon the new rotated bitmap
         hnewbmp&=createcompatiblebitmap(hbmp&,lnewwidth&,lnewheight&)
    
         ''translate each pixel to its new location using standard
         ''rotation algorithm
    
         for i&=0 to lnewheight&
    
           for j&=0 to lnewwidth&
             lsourcex&=(j&+lminx&)*lcosine&+(i&+lminy&)*lsine&
             lsourcey&=(i&+lminy&)*lcosine&-(j&+lminx&)*lsine&
    
             if (lsourcex&=>0) and (lsourcex&<=lwidth&) _
             and (lsourcey&=>0) and (lsourcey&<=lheight&) then
               bitblt(hnewbmp&,j&,i&,1,1,hbmp&, _
                      lsourcex&,lsourcey&,%srccopy)
             end if
    
           next j&
    
         next i&
    
         ''lwidth&=lnewwidth&
         ''lheight&=lnewheight&
    
         deleteobject hbmp&
    
         ''how do I save hnewbmp& to namefile$ ???
    
    
    
         deleteobject hnewbmp&
    
         function=1
    end function
    Jim Seekamp

  • #2
    If you use GRAPHIC ATTACH to do anything to the loaded bitmap, you should be able to use GRAPHIC GET DC to get the device context for that bitmap.

    Also - for the bitmaps creates with the GRAPHIC statements, you may want to use GRAPHIC BITMAP END instead of DeleteObject.
    Adam Drake
    Drake Software

    Comment


    • #3
      The problem is that I'm not using graphic attach - I'm doing absolutely nothing with the bitmap besides rotating the FILE.
      The reason I'm attempting this is that I have the image open in gdiplus, and I can't find any way to rotate a graphic using gdiplus, and I'm not sure that would be as accurate as rotating the file itself. The files I'm attempting to rotate are very large, so I'm concerned about keeping the quality intact.
      Jim Seekamp

      Comment


      • #4
        Just seems I don't have the bandwidth to play with my PowerBasic, however, here are a couple of articles that I think would point you in the right direction...

        Rotating a bitmap in memory: http://www.codeguru.com/cpp/g-m/gdi/article.php/c3693/

        Saving memDC to file: http://www.codeguru.com/cpp/g-m/bitm...cle.php/c1741/

        HTH
        Regards,
        Jules
        Best regards
        Jules
        www.rpmarchildon.com

        Comment


        • #5
          Jim,
          you don't need to use createcompatiblebitmap at all if you don't want to display the bitmap, just load the bitmap directly into your own array, manipulate it and write it back to disk.
          The following program is a quick demo, you'll need to tidy it up. It loads the bitmap specified, rotates it and writes it back to disk.

          Paul.
          Code:
          'PBCC4.0 program#COMPILE EXE
                    
          TYPE BITMAPfile
              signature   AS WORD
              SIZE        AS LONG
              reserved1   AS WORD
              reserved2   AS WORD
              offset      AS LONG
              sizeofheader AS LONG
              WIDTH       AS LONG
              height      AS LONG
              planes      AS WORD
              bitsperpixel AS WORD
              compression AS LONG
              sizeofimage AS LONG
              horizres    AS LONG
              vertres     AS LONG
              colours1    AS LONG
              colours2    AS LONG
          END TYPE
          
          TYPE bit24
              red   AS BYTE
              blue  AS BYTE
              green AS BYTE
          END TYPE
          
          FUNCTION PBMAIN () AS LONG
          
          ff&=FREEFILE
          OPEN "c:/test93.bmp" FOR BINARY AS ff&
          DIM mybitmap AS BITMAPfile
          GET ff&,,mybitmap
          
          'assume a 24 bit colour bitmap
          DIM bitmapdata(1 TO mybitmap.width,1 TO mybitmap.height)   AS bit24
          DIM bitmapdataNew(1 TO mybitmap.width,1 TO mybitmap.height)   AS bit24
          
          GET ff&,mybitmap.offset,bitmapdata()      'get the bitmap data
          
          
          angle##=20   'degrees
          angle##=angle##/(180/3.141592653589)   'convert to radians
          
          'rotate it
          FOR x&=1 TO mybitmap.width
              FOR y& = 1 TO mybitmap.height
                  oldx&=x&*COS(angle##) + y&*SIN(angle##)
                  oldy&=y&*COS(angle##) - x&*SIN(angle##)
                  IF oldx&>0 AND oldx& < mybitmap.width  AND oldy&>0 AND oldy&< mybitmap.height THEN
                      bitmapdataNew(x&,y&)   =  bitmapdata(oldx&,oldy&)
                  END IF
              NEXT
          NEXT
          
          PUT ff&, mybitmap.offset, bitmapdataNew()  'write new data back to bitmap
          
          CLOSE ff&
               
          END FUNCTION

          Comment


          • #6
            [...] I can't find any way to rotate a graphic using gdiplus [...]
            You can use the GdipImageRotateFlip function.
            Last edited by José Roca; 10 Jun 2008, 09:18 PM.
            Forum: http://www.jose.it-berater.org/smfforum/index.php

            Comment


            • #7
              Thanks Paul; that's exactly what I was looking for!!

              Jose, thanks for the heads up... I didn't know about that function. But in the end, for what I'm doing, it's better to change the file and then lock it in my program so it doesn't get rotated again (because of the way I'm using it in my app).
              Jim Seekamp

              Comment

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