2006.04.07 09:56 "Re: [Tiff] LibTiffDelphi problem with WriteEncodedStrip Newbee", by Joris Van Damme

Thorsten,

i want to save images as compressed Tiff. For displaying Images I use the example posted in this list (ReadTiffIntoBitmap) and it really works fine. I read the Faqs, but I can't figure out, how to write compressed Tiff. For example, I want to save an Image as LZW-compressed Tiff. How can I realize that with Delphi/LibTiffDelphi. It may be very easy to make it, but I'm really new in this Tiff-things.

I don't pretend the following to be a universal solution, but it may be
a suitable starting point.

procedure WriteBitmapToTiff(Bitmap: TBitmap; Filename: String);
var
  OpenTiff: PTIFF;
  RowsPerStrip: Longword;
  StripMemory: Pointer;
  StripIndex: Longword;
  StripRowOffset: Longword;
  StripRowCount: Longword;
  ma,mb: PByte;
  nx,ny: Longword;
begin
  if (Bitmap.PixelFormat<>pf24bit) and
     (Bitmap.PixelFormat<>pf32bit) then
    raise Exception.Create('WriteBitmapToTiff is designed for 24bit and
                    32bit bitmaps only');
  RowsPerStrip:=((256*1024) div (Bitmap.Width*3));
  if RowsPerStrip>Bitmap.Height then
    RowsPerStrip:=Bitmap.Height
  else if RowsPerStrip=0 then
    RowsPerStrip:=1;

StripMemory:=GetMemory(RowsPerStrip*Bitmap.Width*3); OpenTiff:=TIFFOpen(PAnsiChar(Filename),'w');

if OpenTiff=nil then
begin
  FreeMemory(StripMemory);
  raise Exception.Create('Unable to create file '''+Filename+'''');
end;

TIFFSetField(OpenTiff,TIFFTAG_IMAGEWIDTH,Bitmap.Width);

TIFFSetField(OpenTiff,TIFFTAG_IMAGELENGTH,Bitmap.Height);

TIFFSetField(OpenTiff,TIFFTAG_PHOTOMETRIC,PHOTOMETRIC_RGB);

TIFFSetField(OpenTiff,TIFFTAG_SAMPLESPERPIXEL,3);

TIFFSetField(OpenTiff,TIFFTAG_BITSPERSAMPLE,8);

TIFFSetField(OpenTiff,TIFFTAG_PLANARCONFIG,PLANARCONFIG_CONTIG);

TIFFSetField(OpenTiff,TIFFTAG_COMPRESSION,COMPRESSION_LZW);

TIFFSetField(OpenTiff,TIFFTAG_PREDICTOR,2);

TIFFSetField(OpenTiff,TIFFTAG_ROWSPERSTRIP,RowsPerStrip); StripIndex:=0;

  StripRowOffset:=0;
  while StripRowOffset<Bitmap.Height do
  begin
    StripRowCount:=RowsPerStrip;
    if StripRowCount>Bitmap.Height-StripRowOffset then
      StripRowCount:=Bitmap.Height-StripRowOffset;
    if Bitmap.PixelFormat=pf24bit then
    begin
      mb:=StripMemory;
      for ny:=StripRowOffset to StripRowOffset+StripRowCount-1 do
      begin
        ma:=Bitmap.ScanLine[ny];
        for nx:=0 to Bitmap.Width-1 do
        begin
          mb^:=PByte(Cardinal(ma)+2)^;
          Inc(mb);
          mb^:=PByte(Cardinal(ma)+1)^;
          Inc(mb);
          mb^:=PByte(Cardinal(ma)+0)^;
          Inc(mb);
          Inc(ma,3);
        end;
      end;
    end
    else
    begin
      mb:=StripMemory;
      for ny:=StripRowOffset to StripRowOffset+StripRowCount-1 do
      begin
        ma:=Bitmap.ScanLine[ny];
        for nx:=0 to Bitmap.Width-1 do
        begin
          mb^:=PByte(Cardinal(ma)+2)^;
          Inc(mb);
          mb^:=PByte(Cardinal(ma)+1)^;
          Inc(mb);
          mb^:=PByte(Cardinal(ma)+0)^;
          Inc(mb);
          Inc(ma,4);
        end;
      end;
    end;
    if TIFFWriteEncodedStrip(OpenTiff,StripIndex,
        StripMemory,StripRowCount*Bitmap.Width*3)=0 then
    begin
      TIFFClose(OpenTiff);
      FreeMemory(StripMemory);
      raise Exception.Create('Failed to write '''+Filename+'''');
    end;
    Inc(StripIndex);
    Inc(StripRowOffset,StripRowCount);
  end;
  TIFFClose(OpenTiff);
  FreeMem(StripMemory);
end;

Best regards,

Joris Van Damme
info@awaresystems.be
http://www.awaresystems.be/
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