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function IntToByte(i: Integer): Byte;
begin
if i > 255 then
Result := 255
else if i < 0 then
Result := 0
else
Result := i;
end;
procedure BmpAlphaBlend(var dBmp: TBitMap; sBmp: TBitmap; Pos: TPoint; Alpha: integer; TranColor: TColor = -1);
type
tagRGBTRIPLE = packed record
rgbtBlue: Byte;
rgbtGreen: Byte;
rgbtRed: Byte;
end;
TRGBTriple = tagRGBTRIPLE;
PRGBTripleArray = ^TRGBTripleArray;
TRGBTripleArray = array[0..32767] of TRGBTriple;
function GetSLColor(pRGB: TRGBTriple): TColor;
begin
Result := RGB(pRGB.rgbtRed, pRGB.rgbtGreen, pRGB.rgbtBlue);
end;
var
p0, p1: PRGBTripleArray;
r, g, b, p, x, y: Integer;
begin
sBmp.PixelFormat := pf24bit;
dBmp.PixelFormat := pf24bit;
if TranColor = -1 then
TranColor := sBmp.Canvas.Pixels[0, 0];
for y := 0 to sBmp.Height - 1 do
if (y + Pos.y >= 0) and (y + Pos.Y < dBmp.Height) then
begin
p0 := dBmp.ScanLine[y + Pos.y];
p1 := sBmp.ScanLine[y];
for x := 0 to sBmp.Width - 1 do
if (x + pos.X >= 0) and (x + Pos.X < dBmp.Width) then
if GetSLCOlor(p1[x]) <> TranColor then
begin
p0[x + pos.X].rgbtRed := IntToByte((p0[x + pos.X].rgbtRed * (100 - Alpha) +
p1[x].rgbtRed * Alpha) div 100);
p0[x + pos.X].rgbtGreen := IntToByte((p0[x + pos.X].rgbtGreen * (100 - Alpha) +
p1[x].rgbtGreen * Alpha) div 100);
p0[x + pos.X].rgbtBlue := IntToByte((p0[x + pos.X].rgbtBlue * (100 - Alpha) +
p1[x].rgbtBlue * Alpha) div 100);
end;
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
brBmp, srcBmp: TBitmap;
begin
//
brBmp := TBitmap.Create;
brBmp.LoadFromFile('c:\a.bmp');
brBmp.PixelFormat := pf24bit;
srcBmp := TBitmap.Create;
srcBmp.LoadFromFile('c:\b.bmp');
srcBmp.PixelFormat := pf24bit;
BmpAlphaBlend(
brBmp, //背景图(大图,也是结果图)
srcBmp, //需要合成的小图
Point(60, 60), //画小图的坐标
100, //半透明度
-1//需要透明的颜色(用于不规则图形,-1就表示以0,0位置的颜色为透明色)
);
canvas.Draw(0, 0, brBmp);
brBmp.Free;
srcBmp.Free;
end;