一个将图像的某个区域之外的区域变暗的函数

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过程名:    DarkBmp
作者:      不得闲
日期:      2009.02.04
参数:      bmp: TBitmap;var DarkRect: TRect;const DarkValue: Integer;const HighValue: Integer = 0
             DarkRect指定不变暗的区域
             DarkValue: 指定暗化的数量值
             HighValue: 指定矩形区域增亮化的数量值
功能：     将图像的某个区域之外的区域变暗的函数
返回值:    无

procedure DarkBmp(bmp: TBitmap;var DarkRect: TRect;const DarkValue: Integer;const HighValue: Integer = 0);var i,j : integer; pB : PByteArray; BmpFormatXs: Integer; w,h:Integer;begin i := Integer(bmp.PixelFormat); if i < 4 then i := 4 else if i = 4 then inc(i) else if i > 7 then i := 7; BmpFormatXs := i - 3; w:= DarkRect.Right - DarkRect.Left; h:= DarkRect.Bottom - DarkRect.Top; if DarkRect.Right > bmp.Width then begin DarkRect.Left:=bmp.Width - w; DarkRect.Right:=bmp.Width; end; if (DarkRect.Bottom > bmp.Height) then begin DarkRect.Top:= bmp.Height - h; DarkRect.Bottom:=bmp.Height; end; if DarkRect.Left <0 then begin DarkRect.Left:=0; DarkRect.Right:=w; end; if DarkRect.Top <0 then begin DarkRect.Top:=0; DarkRect.Bottom:=h; end; for i := 0 to DarkRect.Top - 1 do begin pb:=bmp.ScanLine[i]; for j:=0 to BmpFormatXs*bmp.Width - 1 do if pb[j]<DarkValue then pb[j]:=0 else dec(pb[j],DarkValue); end; for i := DarkRect.Top to bmp.Height - 1 do begin pb:=bmp.ScanLine[i]; for j:=0 to BmpFormatXs*DarkRect.Left - 1 do if pb[j]<DarkValue then pb[j]:=0 else dec(pb[j],DarkValue); end; for i := DarkRect.Bottom to bmp.Height - 1 do begin pb:=bmp.ScanLine[i]; for j:= BmpFormatXs*DarkRect.Left to BmpFormatXs*bmp.Width - 1 do if pb[j]<DarkValue then pb[j]:=0 else dec(pb[j],DarkValue); end; for i := DarkRect.Top to DarkRect.Bottom - 1 do begin pb:=bmp.ScanLine[i]; for j:= BmpFormatXs*DarkRect.Right to BmpFormatXs*bmp.Width - 1 do if pb[j]<DarkValue then pb[j]:=0 else dec(pb[j],DarkValue) end; if HighValue <> 0 then for i := DarkRect.Top to DarkRect.Bottom - 1 do begin pb:=bmp.ScanLine[i]; for j:= BmpFormatXs*DarkRect.Left to BmpFormatXs*DarkRect.Right - 1 do if pb[j]>(255-DarkValue) then pb[j]:=255 else inc(pb[j],HighValue); end;end; 使用方法：procedure TForm1.Button1Click(Sender: TObject);var bmp: TBitmap; r: TRect;begin bmp := TBitmap.Create; bmp.Assign(Image1.Picture.Bitmap); r := Rect(0,0,50,50); DarkBmp(bmp,r,40,10); Image2.Picture.Bitmap := bmp;end;