1 Using Skia's PDF Backend 2 ======================== 3 4 Here is an example of using Skia's PDF backend (SkPDF) via the 5 SkDocument and SkCanvas APIs. 6 7 <!--?prettify lang=cc?--> 8 9 #include "SkDocument.h" 10 11 void WritePDF(SkWStream* outputStream, 12 const char* documentTitle, 13 void (*writePage)(SkCanvas*, int page), 14 int numberOfPages, 15 SkSize pageSize) { 16 SkDocument::PDFMetadata metadata; 17 metadata.fTitle = documentTitle; 18 metadata.fCreator = "Example WritePDF() Function"; 19 SkTime::DateTime now; 20 SkTime::GetDateTime(&now); 21 metadata.fCreation.fEnabled = true; 22 metadata.fCreation.fDateTime = now; 23 metadata.fModified.fEnabled = true; 24 metadata.fModified.fDateTime = now; 25 sk_sp<SkDocument> pdfDocument = SkDocument::MakePDF( 26 outputStream, SK_ScalarDefaultRasterDPI, metadata, 27 nullptr, true); 28 assert(pdfDocument); 29 30 for (int page = 0; page < numberOfPages; ++page) { 31 SkCanvas* pageCanvas = 32 pdfDocument->beginPage(pageSize.width(), 33 pageSize.height()); 34 writePage(pageCanvas, page); 35 pdfDocument->endPage(); 36 } 37 pdfDocument->close(); 38 } 39 40 * * * 41 42 <span id="limits">SkPDF Limitations</span> 43 ------------------------------------------ 44 45 There are several corners of Skia's public API that SkPDF currently 46 does not handle because either no known client uses the feature or 47 there is no simple PDF-ish way to handle it. 48 49 In this document: 50 51 + **drop** means to draw nothing. 52 53 + **ignore** mean to draw without the effect 54 55 + **expand** means to implement something in a non-PDF-ish way. 56 This may mean to rasterize vector graphics, to expand paths with 57 path effects into many individual paths, or to convert text to 58 paths. 59 60 <style scoped><!-- 61 #pdftable {border-collapse:collapse;} 62 #pdftable tr th, #pdftable tr td {border:#888888 2px solid;padding: 5px;} 63 --></style> 64 <table id="pdftable"> 65 <tr><th>Effect</th> <th>text</th> <th>images</th> <th>everything 66 else</th></tr> 67 <tr><th>SkMaskFilter</th> <td>drop</td> <td>ignore</td> <td>ignore</td></tr> 68 <tr><th>SkPathEffect</th> <td>ignore</td> <td>n/a</td> <td>expand</td></tr> 69 <tr><th>SkColorFilter</th> <td>ignore</td> <td>expand</td> <td>ignore</td></tr> 70 <tr><th>SkImageFilter</th> <td>expand</td> <td>expand</td> <td>expand</td></tr> 71 <tr><th>unsupported SkXferModes</th> <td>ignore</td> <td>ignore</td> <td>ignore</td></tr> 72 <tr><th>non-gradient SkShader</th> <td>expand</td> <td>n/a</td> <td>expand</td></tr> 73 </table> 74 75 Notes: 76 77 - *SkImageFilter*: When SkImageFilter is expanded, text-as-text is lost. 78 79 - *SkXferMode*: The following transfer modes are not natively 80 supported by PDF: DstOver, SrcIn, DstIn, SrcOut, DstOut, SrcATop, 81 DstATop, and Modulate. 82 83 Other limitations: 84 85 - *drawText with VerticalText* drop. No known clients seem to make use 86 of the VerticalText flag. 87 88 - *drawTextOnPath* expand. (Text-as-text is lost.) 89 90 - *drawVertices* drop. 91 92 - *drawPatch* drop. 93 94 * * * 95
