覆盖模式处理透明

1、创建一个Mark图层

2、对覆盖区域进行行列扫描（使用背景色，设置透明）

  PRGB = ^TRGB;
  TRGB = record
    b, g, r, a: Byte;
  end;
  PRGBArray = ^TRGBArray;
  TRGBArray = array [0 .. 65565] of TRGB;

        
// use cMask image to remove overlaping rTab area
        slPtr := Integer(cBmp.ScanLine[y1]);
        slSize := Integer(cBmp.ScanLine[y1 + 1]) - slPtr;
        slPtr2 := Integer(cMask.ScanLine[y1]);
        slSize2 := Integer(cMask.ScanLine[y1 + 1]) - slPtr2;
        if i > 0 then
        begin
          for h := y1 to y2 - 1 do
          begin
            Row := PRGBArray(slPtr);
            Row2 := PRGBArray(slPtr2);
            for w := 0 to FTabOverLap - 1 do
              if Row2[w + (FTabWidth - FTabOverLap) + 1].g <> 0 then
              begin
                Row[w + x1].r := Byte(FColorBackground);
                Row[w + x1].g := Byte(FColorBackground shr 8);
                Row[w + x1].b := Byte(FColorBackground shr 16);
                Row[w + x1].A := 0;
              end;
            slPtr := slPtr + slSize;
            slPtr2 := slPtr2 + slSize2;
          end;
        end;
        // overlaping rTab area cleared

Delphi 2009 GDI+ Library

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