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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:
------------------------------------
Attachment: TRITYP4.pdf
DECAHED.pdf
pattern-shading-2-4-idMatrix.pdf
Sorry for bringing bad news, but three other files I tested have no improvement
(decahed and trityp4), or worse - the file pattern-shading-2-4-idMatrix.pdf
displays in about 5 seconds at 96dpi with the current trunk; with your change,
I stopped counting at 60 seconds, so there must be a problem somewhere.
I understand your explanation about the donut this way - if the triangles are
too small, there won't be many different points in a triangle with the same
color. However that explanation probably won't apply to the two files I
mentioned first (which are test files from Adobe). And yes, I agree that our
design with PaintContext and getRaster() shows its weakness with files like
ch14.pdf.
About the stripes in the eci file: this is a problem in axial shading. It is
either the color space (some colorspaces are improperly converted, see
PDFBOX-2142), or an "exotic" transformation matrix, see also PDFBOX-2217 :-( )
> 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, DECAHED.pdf, GWG060_Shading_x1a.pdf, GWG060_Shading_x1a_1.png,
> HSBWHEEL.pdf, McAfee-ShadingType7.pdf, Shadingtype6week1.pdf, TENSOR.pdf,
> TRITYP4.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, ch14.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, example_030.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,
> pattern-shading-2-4-idMatrix.pdf, 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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