Re: [iText-questions] About Soft-Mask

[熊田貢]

Mark,

Thank you very much for your detailed explanation.
I made a code attached, but cannot get a result I 
expected.
I would be happy if you point out what is wrong.

> Hello all,
> 
> I have a question about soft-mask.
> I know there is a sample code "SoftMask.java", but I
> want to know how to achieve soft-mask using gradation
> composed of path lines as mask.
> 
> For example, if I have the following mask;
> 
> for(int i=0; i<10; i++) {
>     template.setLineWidth(10-i);
>     template.setGrayStroke(1-(0.1f*i));
>     template.ellipse(0, 0, 100, 100);
>     template.stroke();
> }
> template.ellipse(0, 0, 100, 100);
> template.clip();

Clipping and masking are two different things.
 
> how to apply the mask to a photo?
> Is it impossible?

No, but it isn't directly supported by iText.  You'll need to read the
PDFReference and do some direct PdfDictionary manipulation.

> 
> I tried "PdfGState#setAlphaIsShape(false)", but I could 
> not get good result.
>

You'll need to create an XObject Form (a PdfTemplate) with the mask shape you
want, and build a "soft mask dictionary", as defined in the Pdf Reference
(chapter 7.5, table 7.10).  Something like this:

<<
/Type /Mask 
/S /Luminosity
/G 999 0 R  %% an indirect reference to that XObject Form I mentioned
>>

You then write this dictionary into the PdfGState's /SMask key.

The XObject Form houses your blended path for the mask.  I strongly suggest you
draw it in DeviceG (gray) color.  You'll need to set the PdfTemplate's
PdfTransparencyGroup.


PdfGState state = new PdfGState();
PdfDictionary maskDict = new PdfDictionary();
maskDict.put( PdfName.TYPE, PdfName.MASK );
maskDict.put( PdfName.S, new PdfName( "Luminosity" ) );
maskDict.put( PdfName.G, template.getIndirectReference() );

state.put( PdfName.SMASK, maskDict );

PdfTransparencyGroup transGroup = new PdfTransparencyGroup();
transGroup.put( PdfName.CS, PdfName.DEVICEGRAY );

template.setGroup( transGroup );

That should do it, though I'm none too certain about the DEVICEGRAY entry in the
transGroup.  It may not be necessary, or it may need to be DEFAULTGRAY instead.

(hmm... I really ought to charge for this stuff ;)

--Mark Storer
  Senior Software Engineer
  Cardiff.com

#include <disclaimer>
typedef std::disclaimer<Cardiff> DisCard;


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SoftMaskTest_01.java
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