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2014.02.04 23:29 "[Tiff] LibTiffDelphi and 1bit tiff", by Martin Masci
2014.02.04 23:41 "Re: [Tiff] LibTiffDelphi and 1bit tiff", by Bob Friesenhahn
2014.02.05 15:35 "Re: [Tiff] LibTiffDelphi and 1bit tiff", by Martin

2014.02.04 23:29 "[Tiff] LibTiffDelphi and 1bit tiff", by Martin Masci

Hi,
I'm using LibTiffDelphi to convert a bitmap image to 1bit tiff image.This is my code:

var  OpenTiff: PTIFF;  RowSize: Longword;  RowsPerStrip: Longword;  StripMemory: Pointer;  StripIndex: Longword;  StripRowOffset: Longword;  StripRowCount: Longword;  mb: PByte;  ny: Longword;  dpi: Double;begin  if (Bitmap.PixelFormat<>pf1bit) then    raise Exception.Create('WriteBitmapToTiff is designed for singlebit bitmaps only');

InvertRect(Bitmap.Canvas.Handle, Bitmap.Canvas.ClipRect); RowSize:=((Bitmap.Width+7) div 8); RowsPerStrip:=((256*1024) div RowSize);

  if RowsPerStrip>Bitmap.Height then    RowsPerStrip:=Bitmap.Height  else if RowsPerStrip=0 then    RowsPerStrip:=1;

StripMemory:=GetMemory(RowsPerStrip*RowSize); OpenTiff:=TIFFOpen(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_MINISWHITE); TIFFSetField(OpenTiff,TIFFTAG_SAMPLESPERPIXEL,1); TIFFSetField(OpenTiff,TIFFTAG_BITSPERSAMPLE,1); TIFFSetField(OpenTiff,TIFFTAG_PLANARCONFIG,PLANARCONFIG_CONTIG); TIFFSetField(OpenTiff,TIFFTAG_COMPRESSION,COMPRESSION_CCITTFAX4);

  // deve essere un double, se si usa un integer non funziona  dpi := 200;  TIFFSetField(OpenTiff,TIFFTAG_XRESOLUTION, dpi);  TIFFSetField(OpenTiff,TIFFTAG_YRESOLUTION, dpi);  TIFFSetField(OpenTiff,TIFFTAG_RESOLUTIONUNIT,RESUNIT_INCH);  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;

      mb:=StripMemory;

      for ny:=StripRowOffset to StripRowOffset+StripRowCount-1 do        begin          CopyMemory(mb,Bitmap.ScanLine[ny],RowSize);          Inc(mb,RowSize);        end;

      if TIFFWriteEncodedStrip(OpenTiff,StripIndex,          StripMemory,StripRowCount*RowSize)=-1 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;

Now I need control threshold to change contrast. In FreeImage for example I can use Threshold(Value) function to change threshold from 0 to 255 value.
How can I edit threshold with LibTiffDelphi?
Thanks