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April 2005

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2005.04.28 13:40 "Delphi 7, TIFF G3/4, Multipage", by Matthias Lach

2005.04.29 16:09 "Re: Delphi 7, TIFF G3/4, Multipage", by Joris Van Damme

2005.04.29 16:09 "Re: Delphi 7, TIFF G3/4, Multipage", by Joris Van Damme

Matthias,

> I can open and see my file with
> "image1.Picture.Bitmap:= ReadTiffIntoBitmap(filename);"
> and can see the TIFF in my Image-Obj on the Form.

ReadTiffIntoBitmap is not part of LibTiffDelphi. It is thus helpful to mention
where it came from...

http://www.asmail.be/msg0055571626.html

ReadTiffIntoBitmap returns a TBitmap. Your calling code now 'owns' the TBitmap.
The statement 'Picture.Bitmap:=x' is the same as 'Picture.Assign(x)'. It does
not transfer ownership of the TBitmap to the TImage, but makes a 'deep copy'
instead (which boils down to incrementation of some usage counters and only a
copy of some small upper-level objects, so is still fast). As a result, your
calling code still owns the original TBitmap... and it fails to Destroy it.
Potentially huge memory leak.

Instead, do something like...
var
  m: TBitmap;
begin
  {add error handling too!!!!!!}
  m:=ReadTiffIntoBitmap(filename);
  image1.Picture.Assign(m);
  m.Free;

> - how can i make a the opened file fit into my Image-Obj ?

TImage has properties like Stretched and stuff... see your Delphi docs.

> - show width, hight, resolution, and pages! (multi-/single-page)

Ask the value of individual tags in a TIFF IFD with TIFFGetField.

For instance, to open a TIFF file, retrieve first page image width, and next
close it again, use this:

var
  OpenTiff: PTIFF;
  FirstPageWidth,FirstPageHeight: Cardinal;
begin
  OpenTiff:=TIFFOpen(Filename,'r');
  if OpenTiff=nil then raise Exception.Create(
           'Unable to open file '''+Filename+'''');
  TIFFGetField(OpenTiff,TIFFTAG_IMAGEWIDTH,@FirstPageWidth);
  TIFFGetField(OpenTiff,TIFFTAG_IMAGELENGTH,@FirstPageHeight);
  TIFFClose(OpenTiff);
  {FirstPageWidth and FirstPageHeigth are now what you are after}

The thing to remember here, is that a TIFF 'image header' is not a fixed set of
fields, like is the case with most image file formats. Instead, it's a set of
tags, and it can contain any tags the writer choose to write. For an overview of
most known tags, see http://www.awaresystems.be/imaging/tiff/tifftags.html.

> - how to cut off lines ?
> - how to raotate?

These are not things that are the responsability of LibTiff. Remember, LibTiff
is a TIFF codec, which means it is able to decode and encode a TIFF file, not
actually do image editing.

The proper way, is to delegate such stuff to things like TBitmap and such. In
Delphi, you would probably do this to open a TIFF, read the first page into a
TBitmap, and next make a second TBitmap that does not include upper two lines
(but this is from the top of my head, and I don't usually use this stuff, so
beware)

var
  m: TBitmap;
  n: TBitmap;
begin
  m:=ReadTiffIntoBitmap(filename);
  n:=TBitmap.Create;
  n.PixelFormat:=m.PixelFormat;
  n.Width:=m.Width;
  n.Height:=m.Height-2;
  n.Canvas.Draw(0,-2,m);
  m.Destroy;
  {n is now your image decoded from filename TIFF file, minus upper two lines}
  {you now own n here, and need to destroy or something in the end}

Same principle goes for rotating and stuff, you don't want to depend on
LibTiffDelphi for that, you'll need to read the Delphi docs and play around with
TBitmap and stuff.

> - what would be the way to handle mulit-part-tiffs?

See http://www.remotesensing.org/libtiff/man/index.html, and more specifically
http://www.remotesensing.org/libtiff/man/TIFFReadDirectory.3tiff.html and
related.



Joris Van Damme
info@awaresystems.be
http://www.awaresystems.be/
Download your free TIFF tag viewer for windows here:
http://www.awaresystems.be/imaging/tiff/astifftagviewer.html