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Date: Sun, 1 Jun 2014 01:29:01 +0000 (UTC)
From: "Shaola Ren (JIRA)" <jira@apache.org>
To: dev@pdfbox.apache.org
Message-ID: <JIRA.12695042.1392312789206.54995.1401586141687@arcas>
In-Reply-To: <JIRA.12695042.1392312789206@arcas>
References: <JIRA.12695042.1392312789206@arcas>
Subject: [jira] [Updated] (PDFBOX-1915) Implement shading with Coons and
 tensor-product patch meshes
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     [ https://issues.apache.org/jira/browse/PDFBOX-1915?page=3Dcom.atlassi=
an.jira.plugin.system.issuetabpanels:all-tabpanel ]

Shaola Ren updated PDFBOX-1915:
-------------------------------

    Attachment: pass4FlagTest.rar

passed the 4 flag test file for shading type 6
code are available at https://bitbucket.org/xinshu/pdfbox.git
for web view https://bitbucket.org/xinshu/pdfbox

> Implement shading with Coons and tensor-product patch meshes
> ------------------------------------------------------------
>
>                 Key: PDFBOX-1915
>                 URL: https://issues.apache.org/jira/browse/PDFBOX-1915
>             Project: PDFBox
>          Issue Type: Improvement
>          Components: Rendering
>    Affects Versions: 1.8.5, 1.8.6, 2.0.0
>            Reporter: Tilman Hausherr
>            Assignee: Shaola Ren
>              Labels: graphical, gsoc2014, java, math, shading
>             Fix For: 2.0.0
>
>         Attachments: CONICAL.pdf, GWG060_Shading_x1a.pdf, HSBWHEEL.pdf, M=
cAfee-ShadingType7.pdf, Shadingtype6week1.pdf, TENSOR.pdf, XYZsweep.pdf, as=
y-coons-but-really-tensor.pdf, asy-tensor-rainbow.pdf, asy-tensor.pdf, coon=
s-function.pdf, coons-function.ps, coons-nofunction-CMYK.pdf, coons-nofunct=
ion-CMYK.ps, coons-nofunction-Duotone.pdf, coons-nofunction-Duotone.ps, coo=
ns-nofunction-Gray.pdf, coons-nofunction-Gray.ps, coons-nofunction-RGB.pdf,=
 coons-nofunction-RGB.ps, coons2-function.pdf, coons2-function.ps, eci_alto=
na-test-suite-v2_technical_H.pdf, lamp_cairo.pdf, pass4FlagTest.rar, patchC=
ases.jpg, patchMap.jpg, shading6ContourTest.rar, shading6Done.rar, updatesh=
ading6ContourTest.rar
>
>
> Of the seven shading methods described in the PDF specification, type 6 (=
Coons patch meshes) and type 7 (Tensor-product patch meshes) haven't been i=
mplemented. I have done type 1, 4 and 5, but I don't know the math for type=
 6 and 7. My math days are decades away.
> Knowledge prerequisites:=20
> - java, although you don't have to be a java ace, just feel confortable
> - math: you should know what "cubic B=C3=A9zier curves", "Degenerate B=C3=
=A9zier curves", "bilinear interpolation", "tensor-product", "affine transf=
orm matrix" and "Bernstein polynomials" are, or be able to learn it
> - maven (basic)
> - svn (basic)
> - an IDE like Netbeans or Eclipse or IntelliJ (basic)
> - ideally, you are either a math student who likes to program, or a compu=
ter science student who is specializing in graphics.
> A first look at PDFBOX: try the command utility here:
> https://pdfbox.apache.org/commandline/#pdfToImage
> and use your favorite PDF, or the PDFs mentioned in PDFBOX-615, these hav=
e the shading types that are already implemented.
> Some simple source code to convert to images:
> String filename =3D "blah.pdf";
> PDDocument document =3D PDDocument.loadNonSeq(new File(filename), null);
> List<PDPage> pdPages =3D document.getDocumentCatalog().getAllPages();
> int page =3D 0;
> for (PDPage pdPage : pdPages)
> {
> ++page;
> BufferedImage bim =3D RenderUtil.convertToImage(pdPage, BufferedImage.TYP=
E_BYTE_BINARY, 300);
> ImageIO.write(bim, "png", new File(filename+page+".png"));
> }
> document.close();
> You are not starting from scratch. The implementation of type 4 and 5 sho=
ws you how to read parameters from the PDF and set the graphics. You don't =
have to learn the complete PDF spec, only 15 pages related to the two shadi=
ng types, and 6 pages about shading in general. The PDF specification is he=
re:
> http://www.adobe.com/devnet/pdf/pdf_reference.html
> The tricky parts are:
> - decide whether a point(x,y) is inside or outside a patch
> - decide the color of a point within the patch
> To get an idea about the code, look at the classes GouraudTriangle, Goura=
udShadingContext, Type4ShadingContext and Vertex here
> https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apach=
e/pdfbox/pdmodel/graphics/shading/
> or download the whole project from the repository.
> https://pdfbox.apache.org/downloads.html#scm
> If you want to see the existing code in the debugger with a Gouraud shadi=
ng, try this file:
> http://asymptote.sourceforge.net/gallery/Gouraud.pdf
> Testing:
> I have attached several example PDFs. To see which one has which shading,=
 open them with an editor like NOTEPAD++, and search for "/ShadingType" (wi=
thout the quotes). If your images are rendering like the example PDFs, then=
 you were successful.
> Optional:
> Review and optimize the complete shading package for speed; implement cub=
ic spline interpolation for type 0 (sampled) functions (that one is really =
low-low priority, see details by looking up "cubic spline interpolation" in=
 the PDF spec, which tells that it is disregarded in printing, and I don't =
have a test PDF).
> Mentor: Tilman Hausherr (European timezone, languages: german, english, f=
rench)


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