چرخش Bitmap در دلفی

[ahmad dehdari]

چرخش Bitmap در دلفی
چرخش Bitmap یک Effect گرافیکی است که دلفی به طور پیش فرض پشتیبانی نمی کند. این مقاله به شما نشان می دهد که چگونه یک تصویر را تا ۹۰ درجه بچرخانید. این کد به شما اجازه می دهد که هر تصویری را ۰ – ۹۰ – ۱۸۰ یا ۲۷۰ درجه بچرخانید. با کمی کار می توان این کد را به گونه تغییر داد که برای هر درجه ای کار کند:
procedure RotateBitmap(var hBitmapDC : Longint; var lWidth : Longint;
var lHeight : Longint; lRadians : real);
var
I : Longint; // loop counter
J : Longint; // loop counter
hNewBitmapDC : Longint; // DC of the new bitmap
hNewBitmap : Longint; // handle to the new bitmap
lSine : extended; // sine used in rotation
lCosine : extended; // cosine used in rotation
X1 : Longint; // used in calculating new
// bitmap dimensions
X2 : Longint; // used in calculating new
// bitmap dimensions
X3 : Longint; // used in calculating new
// bitmap dimensions
Y1 : Longint; // used in calculating new
// bitmap dimensions
Y2 : Longint; // used in calculating new
// bitmap dimensions
Y3 : Longint; // used in calculating new
// bitmap dimensions
lMinX : Longint; // used in calculating new
// bitmap dimensions
lMaxX : Longint; // used in calculating new
// bitmap dimensions
lMinY : Longint; // used in calculating new
// bitmap dimensions
lMaxY : Longint; // used in calculating new
// bitmap dimensions
lNewWidth : Longint; // width of new bitmap
lNewHeight : Longint; // height of new bitmap
lSourceX : Longint; // x pixel coord we are blitting
// from the source image
lSourceY : Longint; // y pixel coord we are blitting
// from the source image begin
// create a compatible DC from the one just brought
// into this function
hNewBitmapDC := CreateCompatibleDC(hBitmapDC);
// 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 := Round(-lHeight * lSine);
Y1 := Round(lHeight * lCosine);
X2 := Round(lWidth * lCosine – lHeight * lSine);
Y2 := Round(lHeight * lCosine + lWidth * lSine);
X3 := Round(lWidth * lCosine);
Y3 := Round(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 width/height of the
// rotated bitmap
hNewBitmap := CreateCompatibleBitmap(hBitmapDC, lNewWidth,
lNewHeight);
//attach the new bitmap to the new device context created
//above before constructing the rotated bitmap
SelectObject(hNewBitmapDC, hNewBitmap);
// loop through and translate each pixel to its new location.
// this is using a standard rotation algorithm
For I := 0 To lNewHeight do begin
For J := 0 To lNewWidth do begin
lSourceX :=
Round((J + lMinX) * lCosine + (I + lMinY) * lSine);
lSourceY :=
Round((I + lMinY) * lCosine – (J + lMinX) * lSine);
If (lSourceX >= 0) And (lSourceX <= lWidth) And
(lSourceY >= 0) And (lSourceY <= lHeight) Then
BitBlt(hNewBitmapDC, J, I, 1, 1, hBitmapDC,
lSourceX, lSourceY, SRCCOPY);
end;
end;
// reset the new bitmap width and height
lWidth := lNewWidth;
lHeight := lNewHeight;
// return the DC to the new bitmap
hBitmapDC := hNewBitmapDC;
// destroy the bitmap created
DeleteObject(hNewBitmap);
End;




یک مثال از طریقه استفاده از این تابع را ببینید:
procedure TForm1.RotateTest(Sender: TObject);
var
lRadians : real;
DC : longint;
H, W : integer;
Degrees : integer;
begin
Degrees := 45;
lRadians := PI * Degrees / 180;
DC := Image1.Picture.Bitmap.Canvas.Handle;
H := Image1.Picture.Bitmap.Height;
W := Image1.Picture.Bitmap.Width;
RotateBitmap(DC, W, H, lRadians);
Image1.Width := W;
Image1.Height := H;
Image1.Picture.Bitmap.Width := W;
Image1.Picture.Bitmap.Height := H;
BitBlt(Image1.Picture.Bitmap.Canvas.Handle, 0, 0, W, H, DC, 0, 0, SRCCopy);
Image1.Refresh;
end;