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https://issues.apache.org/jira/browse/PDFBOX-1915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14045578#comment-14045578
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Tilman Hausherr commented on PDFBOX-1915:
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I see you've been active with refactoring, this is good :-)
Yes the javadocs should be done too. It doesn't have to be long, but it should
be a summary of whats being done / how it is being used by other classes if it
is an interface or an abstract class. Nobody likes to do it, but the more you
wait, the more annoying it becomes to do, so don't wait :-)
Private classes are not required to have a javadoc, but they should have an
explanation if it isn't obvious from the code. Or at least a hint of whats
being done. E.g. " getLen" => length of a line. "isEdgeALine" -> would like to
know.
If you used a wikipedia article, or an online paper as help, include the link
where applicable. I couldn't have done types 1, 4, 5 without wikipedia and at
one university course resource :-)
- CoordinateColorPair.java: classes that are used only by you don't have to be
public. Just leave out the keyword "public".
- PatchMeshesShadingContext.java readPatch(): if I remember this correctly, an
EOF at that place is a bug in the source file (the flag was read successfully
but not the rest), thus LOG.ERROR.
- that "decode" line you commented out: just remove it
- setLevel: this isn't a setter, it isn't a getter, I suggest you name it
"calculateLevel" or whatever. I assume this is what we discussed about here,
i.e. you're making a decision how far you'll chop the patch into triangles
depending on the size of the patch.
- remove classes that have a comment "This class is not used" :-) Just delete
them.
I'll run the code tonight and/or this weekend and give more feedback.
https://www.youtube.com/watch?v=TiqDqd-1pwU
watch at 29:00 he shows the patch on the top right of the file TENSOR.PDF, and
it seems you did the correct implementation :-)
The stuff at 22:00 is also about shading, but I feel that this goes over the
scope of this project. I don't even know if we support "knockout transparency
groups", we just started with transparency groups a week ago or so.
> 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: CIB-coons-vs-tensormesh.pdf, CIB-coonsmesh.pdf,
> CONICAL.pdf, GWG060_Shading_x1a.pdf, GWG060_Shading_x1a_1.png, HSBWHEEL.pdf,
> McAfee-ShadingType7.pdf, Shadingtype6week1.pdf, TENSOR.pdf, XYZsweep.pdf,
> _gwg060_shading_x1a.pdf-1.png, _mcafee-shadingtype7.pdf-1.png,
> asy-coons-but-really-tensor.pdf, asy-tensor-rainbow.pdf, asy-tensor.pdf,
> coons-function.pdf, coons-function.ps, coons-nofunction-CMYK.pdf,
> coons-nofunction-CMYK.ps, coons-nofunction-Duotone.pdf,
> coons-nofunction-Duotone.ps, coons-nofunction-Gray.pdf,
> coons-nofunction-Gray.ps, coons-nofunction-RGB.pdf, coons-nofunction-RGB.ps,
> coons2-function.pdf, coons2-function.ps, coons4-function.ps, crestron-p9.pdf,
> eci_altona-test-suite-v2_technical_H.pdf, failedTest.rar, lamp_cairo.pdf,
> lamp_cairo7_0.png, lamp_cairo7_1.png, lamp_cairo7_1.png,
> lineRasterization.jpg, mcafeeU5.pdf, mcafeeU5_1.png, mcafeeu5.pdf-1.png,
> pass4FlagTest.rar, patchCases.jpg, patchMap.jpg, shading6ContourTest.rar,
> shading6Done.rar, shading7.rar, tensor-nofunction-RGB.pdf,
> tensor-nofunction-RGB.ps, tensor-nofunction-RGB_1.png,
> tensor4-nofunction.pdf, tensor4-nofunction.ps, tensor4-nofunction_1.png,
> updateshading6ContourTest.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
> implemented. 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:
> - 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.
> 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 have
> the shading types that are already implemented.
> Some simple source code to convert to images:
> String filename = "blah.pdf";
> PDDocument document = PDDocument.loadNonSeq(new File(filename), null);
> List<PDPage> pdPages = document.getDocumentCatalog().getAllPages();
> int page = 0;
> for (PDPage pdPage : pdPages)
> {
> ++page;
> BufferedImage bim = RenderUtil.convertToImage(pdPage,
> BufferedImage.TYPE_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 shows
> 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 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.
> https://pdfbox.apache.org/downloads.html#scm
> If you want to see the existing code in the debugger with a Gouraud shading,
> 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"
> (without 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 cubic
> 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,
> french)
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