SVGirl

Overview

SVGirl stands for SVG Instant Rendering Library, and it is a library for parsing SVG files into a simplified internal representation suitable for display or manipulation, derived from libsvgtiny, with focus on minimal dependencies and embedded systems.

The overall idea of the library is to take some SVG as input, and return a list of paths and texts which can be rendered easily. The library does not do the actual rendering.

All supported SVG objects, for example circles, lines, and gradient filled shapes, are converted to flat-filled paths or a fragment of text, and all coordinates are converted, transformed etc. to pixels.

SVGirl is freely redistributed under MIT License

SVG support

SVGirl is initially aiming to implement SVG Tiny, as defined in Scalable Vector Graphics (SVG) Tiny Specification.

SVG Tiny elements supported: defs, g, svg, circle, line, path, polygon, polyline, rect, text

SVG Tiny elements not yet supported: desc, metadata, title, use, a, switch, ellipse, image, font, font-face, font-face-name, font-face-src, glyph, hkern, missing-glyph, animate, animateColor, animateMotion, animateTransform, mpath, set, foreignObject

Additional elements supported: linearGradient, stop

Text support is incomplete: no fonts. linearGradient support is incomplete: They parse, but the internal data structure doesn't (yet) represent the gradient.

The style attribute is supported.

Building SVGirl

Compile all source along with test programs:

make

Launch test suite:

make check

Build reference SVG viewer on X Window System:

make bin/display_x11

Using SVGirl

The interface is in the header svgtiny.h

#include "svgtiny.h"

First create a svgtiny_diagram using svgtiny_create():

struct svgtiny_diagram *diagram;
diagram = svgtiny_create();

This will return a pointer to a new diagram, or NULL if there was not enough memory.

SVGs are parsed from memory using svgtiny_parse():

svgtiny_code code = svgtiny_parse(diagram, buffer, size, url, 1000, 1000);

The arguments are the pointer returned by svgtiny_create(), a buffer containing the SVG data, the size of the SVG in bytes, the url that the SVG came from, and the target viewport width and height in pixels.

The function returns svgtiny_OK if there were no problems, and diagram is updated. The diagram can then be rendered by looping through the array diagram->shape[0..diagram->shape_count]:

for (unsigned int i = 0; i != diagram->shape_count; i++) {

Path shapes have a non-NULL path pointer. The path is an array of floats of length path_length. The array contains segment type codes followed by 0 to 3 pairs of coordinates (depending on the segment type):

• svgtiny_PATH_MOVE x y
• svgtiny_PATH_CLOSE
• svgtiny_PATH_LINE x y
• svgtiny_PATH_BEZIER x1 y1 x2 y2 x3 y3

A path always starts with a MOVE.

The fill and stroke attributes give the colors of the path, or svgtiny_TRANSPARENT if the path is not filled or stroked. Colors are in 0xRRGGBB format (depending on endianness). The macros svgtiny_RED, svgtiny_GREEN, and svgtiny_BLUE can be used to extract the components.

The width of the path is in stroke_width.

Text shapes have a NULL path pointer and a non-NULL text pointer. Text is in UTF-8. The coordinates of the text are in text_x, text_y. Text colors and stroke width are as for paths.

If memory runs out during parsing, svgtiny_parse() returns svgtiny_OUT_OF_MEMORY, but the diagram is still valid up to the point when memory was exhausted, and may safely be rendered.

If there is an error in the SVG (for example, an element is missing an attribute required by the specification), svgtiny_SVG_ERROR is returned, but the diagram is still valid up to the point of the error. The error is recorded in diagram->error_message and the line that caused it in diagram->error_line.

svgtiny_LIBDOM_ERROR indicates that parsing the XML failed. The returned diagram will contain no shapes. svgtiny_NOT_SVG means that the XML did not contain a top-level element.

To free memory used by a diagram, use svgtiny_free():

svgtiny_free(diagram);

For an example, see examples/svgtiny_display_x11.c.