Some micro optimizations for BlendMaskLine and ReduceOpacity

source/Img32.pas

@@ -1269,6 +1269,8 @@ function BlendMask(bgColor, alphaMask: TColor32): TColor32;
 {$RANGECHECKS OFF} // negative array index is used
 
 procedure BlendMaskLine(bgColor, alphaMask: PColor32; width: nativeint);
+label
+ SkipNone32;
 var
  a: byte;
 begin
@@ -1283,13 +1285,22 @@ procedure BlendMaskLine(bgColor, alphaMask: PColor32; width: nativeint);
  // common values.
  while width < 0 do
  begin
+ // MulTable[0, fgA] -> 0, if bgColor is already 0 => skip
+ while PStaticARGBArray(bgColor)[width].Color = 0 do
+ begin
+SkipNone32:
+ inc(width);
+ if width = 0 then exit;
+ end;
  a := PStaticARGBArray(bgColor)[width].A;
  // MulTable[0, fgA] -> 0 => replace color with 0
  while a = 0 do
  begin
  PStaticColor32Array(bgColor)[width] := 0;
  inc(width);
  if width = 0 then exit;
+ if PStaticARGBArray(bgColor)[width].Color = 0 then
+ goto SkipNone32;
  a := PStaticARGBArray(bgColor)[width].A;
  end;
  // MulTable[255, fgA] -> fgA => replace alpha with fgA
@@ -3707,12 +3718,15 @@ procedure TImage32.ReduceOpacity(opacity: Byte);
 var
  i: Integer;
  c: PARGB;
+ a: Byte;
 begin
  if opacity = 255 then Exit;
  c := PARGB(PixelBase);
  for i := 0 to Width * Height -1 do
  begin
- c.A := MulTable[c.A, opacity];
+ a := c.A;
+ if a <> 0 then
+ c.A := MulTable[a, opacity];
  inc(c);
  end;
  Changed;
@@ -3723,19 +3737,24 @@ procedure TImage32.ReduceOpacity(opacity: Byte; rec: TRect);
 var
  i,j, rw: Integer;
  c: PARGB;
+ a: Byte;
+ lineOffsetInBytes: integer;
 begin
  Types.IntersectRect(rec, rec, bounds);
  if IsEmptyRect(rec) then Exit;
  rw := RectWidth(rec);
  c := @Pixels[rec.Top * Width + rec.Left];
- for i := rec.Top to rec.Bottom -1 do
+ lineOffsetInBytes := (Width - rw) * SizeOf(TARGB);
+ for i := rec.Top to rec.Bottom - 1 do
  begin
  for j := 1 to rw do
  begin
- c.A := MulTable[c.A, opacity];
+ a := c.A;
+ if a <> 0 then
+ c.A := MulTable[a, opacity];
  inc(c);
  end;
- inc(c, Width - rw);
+ inc(PByte(c), lineOffsetInBytes);
  end;
  Changed;
 end;