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https://issues.apache.org/jira/browse/PDFBOX-1915?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tilman Hausherr updated PDFBOX-1915:
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Attachment: XYZsweep.pdf
lamp_cairo.pdf
asy-coons-but-really-tensor.pdf
asy-tensor.pdf
> 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: 2.0.0
> Reporter: Tilman Hausherr
> Labels: graphical, gsoc2014, java, math, shading
> Attachments: XYZsweep.pdf, asy-coons-but-really-tensor.pdf,
> asy-tensor.pdf, lamp_cairo.pdf
>
>
> 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
> implemented. I have done type 4 and 5, but I don't know the math for type 6
> and 7. My math days are decades away.
> Knowledge prerequisites:
> - java, although you don't have to be a java ace, just feel confortable
> - math: you should know what "cubic Bézier curves", "Degenerate Bézier
> curves, "bilinear interpolation", "tensor-product", "affine transform 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 computer
> science student who is specializing in graphics.
> You are not starting from scratch. The implementation of type 4 and 5 shows
> you how to do the basics (read the parameters from the PDF, set the
> graphics), except for the math. You don't have to learn the complete PDF
> spec, only 15 pages related to the two shading types, and 6 pages about
> shading in general. The PDF specification is here:
> 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,
> GouraudShadingContext, Type4ShadingContext and Vertex here
> https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/graphics/shading/
> or download the whole project from the repository.
> Testing:
> I will attach several example PDFs. To see which one has which shading, open
> them with an editor like NOTEPAD++, and search for "/ShadingType" (without
> the quotes). If your images are rendering like the example PDFs, then you
> were successful.
> Optional:
> Review and optimize the complete shading package
> Mentor: Tilman Hausherr (European timezone, languages: german, english,
> french)
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