Wt

h1. Tips and Tricks

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h3. Making a hard-copy of painted graphics

The primary use for the Wt painting API is to paint on a WPaintedWidget. Internally, this uses either a VML, SVG or HTML 5 canvas painting device to deliver the painting to the browser.

It is also possible to paint directly to an SVG image, which is a standardized generic vector graphics format, and increasingly supported by various tools.

You could use the SVG image as a starting point for exporting the painted graphics to raster format. Using the "imagemagick":http://www.imagemagick.org/script/index.php or "graphicsmagick":http://www.graphicsmagick.org/ libraries, you can convert from SVG to other formats using the library API or using the command line 'convert' tool. Using "inkscape":http://www.inkscape.org/, a sophisticated SVG editor, you may get high quality SVG rendering (with, compared to imagemagick, much better font support) from the command-line (see the manpage). Another option may be "librsvg":http://librsvg.sourceforge.net.

The WSvgImage class allows you to easily create an SVG image, and save it to a (file) stream, using the following template:

<pre>

WSvgImage image(400, 300);

WPainter painter(&image);

// paint things on the painter, like you normally do in WPaintedWidget::paintEvent().

//

// e.g. you could do WCartesianChart *c = ...

// c->paint(painter);

painter.end();

std::ofstream f("image.svg");

image.write(f);

f.close();

</pre>