Stretched bitmap on TPrinter

I'm writing a program that prints a bitmap to the printer via TPrinter object. The problem occurs when I "stretch" the bitmap to fit the adequate area on paper. Due to the stretching (bitblts to Printer's DC), dotted patterns appear on the bitmap regions, making them almost gray.

This is an obvius undesired effect. Does anybody knows some approach to help me?

Try this:

procedure DrawImage(Canvas: TCanvas; DestRect: TRect; ABitmap:

TBitmap);

var

Header, Bits: Pointer;

HeaderSize: Integer;

BitsSize: Longint;

begin

GetDIBSizes(ABitmap.Handle, HeaderSize, BitsSize);

Header := MemAlloc(HeaderSize);

Bits := MemAlloc(BitsSize);

try

GetDIB(ABitmap.Handle, ABitmap.Palette, Header^, Bits^);

StretchDIBits(Canvas.Handle, DestRect.Left, DestRect.Top,

DestRect.Right, DestRect.Bottom,

0, 0, ABitmap.Width, ABitmap.Height, Bits,TBitmapInfo(Header^),

DIB_RGB_COLORS, SRCCOPY);

{ you might want to try DIB_PAL_COLORS instead, but this is well

beyond the scope of my knowledge. }

finally

MemFree(Header, HeaderSize);

MemFree(Bits, BitsSize);

end;

{ Print a Bitmap using the whole Printerpage }

procedure PrintBitmap(ABitmap: TBitmap);

var

relheight, relwidth: integer;

begin

screen.cursor := crHourglass;

Printer.BeginDoc;

if ((ABitmap.width / ABitmap.height) > (printer.pagewidth /printer.pageheight)) then

begin

{ Stretch Bitmap to width of Printerpage }

relwidth := printer.pagewidth;

relheight := MulDiv(ABitmap.height, printer.pagewidth,ABitmap.width);

end else

begin

{ Stretch Bitmap to height of Printerpage }

relwidth := MulDiv(ABitmap.width, printer.pageheight, ABitmap.height);

relheight := printer.pageheight;

end;

DrawImage(Printer.Canvas, Rect(0, 0, relWidth, relHeight), ABitmap);

Printer.EndDoc;

screen.cursor := crDefault;

end;