取得图片的透明区域

(*//============================================================================

设计思路:～～

就是对画布一行一行的扫描～～

对于不是透明色相连的像素都看成一条条的线段～～

───────── ─ ─── ─────

─────── ──── ───────

─── ─── ── ───────

── ─────────

用这些线段组合成不规则的区域～～

线段就是找到开始位置和结束位置就行了～～

组合区域是最花时间的地方～～

减少组合区域的频率就可以提高运行的速度～～

用线段组合就比用点组合少多了～～

============================================================================//*)

function GraphicToRGN(mGraphic: TGraphic; mTransPoint: TPoint): HRGN;

var

I, J: Integer;

vStart: Integer;

vHandle: HRGN;

vTransColor: TColor;

begin

Result := 0;

if not Assigned(mGraphic) then Exit;

Result := CreateRectRgn(0, 0, 0, 0);

with TBitmap.Create do try

Width := mGraphic.Width;

Height := mGraphic.Height;

Canvas.Draw(0, 0, mGraphic);

vTransColor := Canvas.Pixels[mTransPoint.X, mTransPoint.Y];

for I := 0 to Height - 1 do begin

vStart := 0;

for J := 0 to Width do begin

if (Canvas.Pixels[J, I] <> vTransColor) and (J < Width) then

if vStart < 0 then

vStart := J

else

else if vStart >= 0 then begin

vHandle := CreateRectRgn(vStart, I, J, I + 1);

try

CombineRgn(Result, Result, vHandle, RGN_OR);

finally

DeleteObject(vHandle);

end;

vStart := -1;

end;

end;

end;

finally

Free;

end;

end; { GraphicToRGN }

//Example

procedure TForm1.Button1Click(Sender: TObject);

var

vRGN: HRGN;

begin

BorderStyle := bsNone;

Image1.Left := 0;

Image1.Top := 0;

vRGN := GraphicToRGN(Image1.Picture.Graphic, Point(0, 0));

try

SetWindowRgn(Handle, vRGN, True);

finally

DeleteObject(vRGN);

end;

end;