Delphi常见图象格式转换技术(二)

(b[0] >= lb) and (b[0] <= hb) then
Break; // pixel is transparent
Inc(x);
end;
{ test to see if we have a non-transparent area in the image }
if x > x0 then
begin
{ increase RgnData by AllocUnit rects if we exceeds maxRects }
if RgnData^.rdh.nCount >= maxRects then
begin
Inc(maxRects,AllocUnit);
ReallocMem(RgnData,SizeOf(RGNDATAHEADER) (SizeOf(TRect) * MaxRects));
end;
{ Add the rect (x0, y)-(x, y 1) as a new visible area in the region }
pr := @RgnData^.Buffer; // Buffer is an array of rects
with RgnData^.rdh do
begin
SetRect(pr[nCount], x0, y, x, y 1);
{ adjust the bound rectangle of the region if we are "out-of-bounds" }
if x0 < rcBound.Left then rcBound.Left := x0;
if y < rcBound.Top then rcBound.Top := y;
if x > rcBound.Right then rcBound.Right := x;
if y 1 > rcBound.Bottom then rcBound.Bottom := y 1;
Inc(nCount);
end;
end; // if x > x0


if RgnData^.rdh.nCount = 2000 then
begin
h := ExtCreateRegion(nil, SizeOf(RGNDATAHEADER) (SizeOf(TRect) * maxRects), RgnData^);
if Result > 0 then
begin // Expand the current region
CombineRgn(Result, Result, h, RGN_OR);
DeleteObject(h);
end
else // First region, assign it to Result
Result := h;
RgnData^.rdh.nCount := 0;
SetRect(RgnData^.rdh.rcBound, MAXLONG, MAXLONG, 0, 0);
end;
Inc(x);
end; // scan every sample byte of the image
Inc(Integer(ScanLinePtr), ScanLineInc);
end;
{ need to call ExCreateRegion one more time because we could have left }
{ a RgnData with less than 2000 rects, so it wasn''''t yet created/combined }
h := ExtCreateRegion(nil, SizeOf(RGNDATAHEADER) (SizeOf(TRect) * MaxRects), RgnData^);
if Result > 0 then
begin
CombineRgn(Result, Result, h, RGN_OR);
DeleteObject(h);
end
else
Result := h;
finally
FreeMem(RgnData,SizeOf(RGNDATAHEADER) (SizeOf(TRect) * MaxRects));
end;

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