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diff --git a/docs/design/understanding/svg.xml b/docs/design/understanding/svg.xml new file mode 100644 index 000000000..7fd19f369 --- /dev/null +++ b/docs/design/understanding/svg.xml @@ -0,0 +1,57 @@ +<?xml version="1.0" standalone="no"?> +<!-- Overview --> +<document> + <header> + <title>SVG</title> + <subtitle>All you wanted to know about SVG and FOP !</subtitle> + <authors> <person name="Keiron Liddle" email="keiron@aftexsw.com"/> + </authors> + </header> + <body><s1 title="SVG"> + <p>SVG is rendered through Batik.</p><p>The XML from the XSL:FO document + is converted into an SVG DOM with batik. This DOM is then set as the Document + on the Foreign Object area in the Area Tree.</p><p>This DOM is then available to + be rendered by the renderer.</p><p>SVG is rendered in the renderers via an + XMLHandler in the FOUserAgent. This XML handler is used to render the SVG. The + SVG is rendered by using batik. Batik converts the SVG DOM into an internal + structure that can be drawn into a Graphics2D. So for PDF we use a + PDFGraphics2D to draw into.</p><p>This creates the necessary PDF information to + create the SVG image in the PDF document.</p><p>Most of the work is done in the + PDFGraphics2D class. There are also a few bridges that are plugged into batik + to provide different behaviour for some SVG elements.</p><s2 + title="Text Drawing"><p>Normally batik converts text into a set of curved + shapes. </p><p>This is handled as any other shapes when rendering to the output. This + is not always desirable as the shapes have very fine curves. This can cause the + output to look a bit bad in PDF and PS (it can be drawn properly but is not by + default). These curves also require much more data than the original + text.</p><p>To handle this there is a PDFTextElementBridge that is set when + using the bridge in batik. If the text is simple enough for the text to be + drawn in the PDF as with all other text then this sets the TextPainter to use + the PDFTextPainter. This inserts the text directly into the PDF using the + drawString method on the PDFGraphics2D.</p><p>Text is considered simple if the + font is available, the font size is useable and there are no tspans or other + complications. This can make the resulting PDF significantly + smaller.</p></s2><s2 title="PDF Links"><p>To support links in PDF another batik + element bridge is used. The PDFAElementBridge creates a PDFANode which inserts + a link into the PDF document via the PDFGraphics2D.</p><p>Since links are + positioned on the page without any transforms then we need to transform the + coordinates of the link area so that they match the current position of the a + element area. This transform may also need to account for the svg being + positioned on the page.</p></s2><s2 title="Images"><p>Images are normally drawn + into the PDFGraphics2D. This then creates a bitmap of the image data that can + be inserted into the PDF document. </p><p>As PDF can support jpeg images then another + element bridge is used so that the jpeg can be directly inserted into the + PDF.</p></s2><s2 title="PDF Transcoder"><p>Batik provides a mechanism to + convert SVG into various formats. Through FOP we can convert an SVG document + into a single paged PDF document. The page contains the SVG drawn as best as + possible on the page. There is a PDFDocumentGraphics2D that creates a + standalone PDF document with a single page. This is then drawn into by batik in + the same way as with the PDFGraphics2D.</p></s2><s2 + title="Other Outputs"><p>When rendering to AWT the SVG is simply drawn onto the + awt canvas using batik.</p><p>The PS Renderer uses a similar technique as the + PDF Renderer.</p><p>The SVG Renderer simply embeds the SVG inside an svg + element.</p></s2><s2 title="Associated Tasks"><ul><li>To get accurate drawing + pdf transparency is needed.</li><li>The drawRenderedImage methods need + implementing.</li><li>Handle colour space better.</li><li>Improve link handling + with pdf.</li><li>Improve image handling.</li></ul></s2></s1> + </body></document>
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