ThorVG

ThorVG is a platform-independent portable library for drawing vector-based scenes and animation. It's open-source software that is freely used by a variety of software platforms and applications. ThorVG provides neat and easy APIs. Its library has no dependencies and keeps a super compact size. It serves as the vector graphics engine for Tizen OS that powers many products.

The following list shows primitives that are supported by ThorVG:

• Shapes: Line, Arc, Curve, Path, Polygon, ...
• Filling: Solid, Linear and Radial Gradient
• Scene Graph & Affine Transformation (translation, rotation, scale, ...)
• Stroking: Width, Join, Cap, Dash
• Composition: Blending, Masking, Path Clipping, ...
• Pictures: TVG, SVG, JPG, PNG, Bitmap

If your program has the main renderer, your program could call ThorVG APIs while switching drawing contexts between the main renderer and ThorVG. During the API calls, ThorVG serializes drawing commands among the volatile paints' nodes then performs synchronous/asynchronous rendering using its backend raster engines. ThorVG supports vector images such as SVG, also expands, supporting other popular formats on demand. On the rendering, it could spawn intermediate frame-buffers for compositing scenes only when it's necessary. The next figure shows you a brief strategy on how to use ThorVG on your system.

Contents

• Building ThorVG
  • Meson Build
• Quick Start
• SVG
• TVG Picture
• Practices
  • Tizen
  • Rive
• Examples
• Tools
  • ThorVG Viewer
  • SVG to PNG
  • SVG to TVG
• API Bindings
• Issues or Feature Requests

Building ThorVG

ThorVG supports meson build system.

Meson Build

Install meson and ninja if not already installed.

Run meson to configure ThorVG:

meson build

Run ninja to build & install ThorVG:

ninja -C build install

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Quick Start

ThorVG renders vector shapes to a given canvas buffer. The following is a quick start to show you how to use the essential APIs.

First, you should initialize the ThorVG engine:

tvg::Initializer::init(tvg::CanvasEngine::Sw, 0);   //engine method, thread count

Then it would be best if you prepared an empty canvas for drawing on it:

static uint32_t buffer[WIDTH * HEIGHT];                                 //canvas target buffer

auto canvas = tvg::SwCanvas::gen();                                     //generate a canvas
canvas->target(buffer, WIDTH, WIDTH, HEIGHT, tvg::SwCanvas::ARGB8888);  //buffer, stride, w, h, Colorspace

Next you can draw multiple shapes on the canvas:

auto rect = tvg::Shape::gen();               //generate a shape
rect->appendRect(50, 50, 200, 200, 20, 20);  //define it as a rounded rectangle (x, y, w, h, rx, ry)
rect->fill(100, 100, 100, 255);              //set its color (r, g, b, a)
canvas->push(move(rect));                    //push the rectangle into the canvas

auto circle = tvg::Shape::gen();             //generate a shape
circle->appendCircle(400, 400, 100, 100);    //define it as a circle (cx, cy, rx, ry)

auto fill = tvg::RadialGradient::gen();      //generate a radial gradient
fill->radial(400, 400, 150);                 //set the radial gradient geometry info (cx, cy, radius)

tvg::Fill::ColorStop colorStops[2];          //gradient colors
colorStops[0] = {0.0, 255, 255, 255, 255};   //1st color values (offset, r, g, b, a)
colorStops[1] = {1.0, 0, 0, 0, 255};         //2nd color values (offset, r, g, b, a)
fill->colorStops(colorStops, 2);             //set the gradient colors info

circle->fill(move(fill));                    //set the circle fill
canvas->push(move(circle));                  //push the circle into the canvas

This code generates the following result:

You can also draw you own shapes and use dashed stroking:

auto path = tvg::Shape::gen();               //generate a path
path->moveTo(199, 34);                       //set sequential path coordinates
path->lineTo(253, 143);
path->lineTo(374, 160);
path->lineTo(287, 244);
path->lineTo(307, 365);
path->lineTo(199, 309);
path->lineTo(97, 365);
path->lineTo(112, 245);
path->lineTo(26, 161);
path->lineTo(146, 143);
path->close();

path->fill(150, 150, 255, 255);              //path color

path->stroke(3);                             //stroke width
path->stroke(0, 0, 255, 255);                //stroke color
path->stroke(tvg::StrokeJoin::Round);        //stroke join style
path->stroke(tvg::StrokeCap::Round);         //stroke cap style

float pattern[2] = {10, 10};                 //stroke dash pattern (line, gap)
path->stroke(pattern, 2);                    //set the stroke pattern

canvas->push(move(path));                    //push the path into the canvas

The code generates the following result:

Now begin rendering & finish it at a particular time:

canvas->draw();
canvas->sync();

Then you can acquire the rendered image from the buffer memory.

Lastly, terminate the engine after its usage:

tvg::Initializer::term(tvg::CanvasEngine::Sw);

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SVG

ThorVG supports SVG (Scalable Vector Graphics) rendering through its SVG interpreter. It satisfies the SVG Tiny Specification to keep it lightweight, so it's useful for the embedded systems. Among the SVG Tiny specs, unsupported features in the ThorVG are the following:

• Animation
• Fonts & Text
• Interactivity
• Multimedia
• Scripting

The following code snippet shows how to draw SVG image using ThorVG:

auto picture = tvg::Picture::gen();         //generate a picture
picture->load("tiger.svg");                 //load SVG file
canvas->push(move(picture));                //push the picture into the canvas

The result:

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TVG Picture

ThorVG provides the designated vector data format which is called TVG Picture. TVG Picture stores a list of properties of the Paint nodes of a scene in binary form. The data saved in a TVG Picture is optimized beforehand, keeping the resulting file small and the data loading process fast and efficient.

To save data in a TVG Picture format, ThorVG uses a dedicated module - TVG Saver. It is responsible for optimizing the data of all the scene-tree nodes and saving them in binary format. In the optimization process, the TVG Saver filters out unused information, removing the duplicated properties, merges the overlapping shapes and compresses the data if possible, but keeping the TVG Pictures compatible with the later version of ThorVG libraries. In case of compression, it uses Lempel-Ziv-Welchi data compression algorithm.

The final data size is smaller in comparison to any other text-based vector data format, such as SVG, which in turn decreases the required application resources. This helps not only reduce the number of I/O operations but also reduces the memory bandwidth while loading the data. Thus this is effective if your program uses a big amount of the vector resources.

Additionally, TVG Picture helps to reduce the resource loading tasks since it can skip interpreting the data stage. That brings the reduced amount of the required runtime memory and rendering tasks that increases the performance.

Utilizing the TVG Picture allows you to reduce the data size and loading time by more than 30%, on average (See More). Note that the charge in the performance rate depends on the resource size and its complexity.

While TVG Saver exports the scene-tree to the TVG Picture data files(TVG), the TVG Loader imports and restores it to the programmable instances. You can quickly use the ThorVG Viewer to convert files from SVG to TVG.

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Practices

Tizen

ThorVG is integrated into the Tizen platform as the vector graphics engine. It's being used for vector primitive drawings and scalable image contents such as SVG and Lottie Animation among the Tizen powered products.

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Rive

We're also building a Rive port that supports Rive Animation run through the ThorVG backend. Rive is a brand new animation platform that supports fancy, user-interactive vector animations. For more details see Rive-Tizen on Github.

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Examples

There are various examples available in thorvg/src/examples to help you understand ThorVG APIs.

To execute these examples, you can build them with the following meson option:

meson -Dexamples=true . build

Note that these examples require the EFL elementary package for launching. If you're using Linux-based OS, you can easily install this package from your OS distribution server. Otherwise, please visit the official EFL page for more information.

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Tools

ThorVG Viewer

ThorVG provides the resource verification tool for the ThorVG Engine. ThorVG viewer does immediate rendering via web browser running on the ThorVG web-assembly binary, allowing real-time editing of the vector elements on it. It doesn't upload your resources to any external server while allowing to export to supported formats such as TVG, so the designer resource copyright is protected.

thorvg-viewer-demo.mp4

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SVG to PNG

ThorVG provides an executable svg2png converter that generates a PNG file from an SVG file.

To use the svg2png, you must turn on this feature in the build option:

meson -Dtools=svg2png . build

Alternatively, you can add the svg2png value to the tools option in meson_option.txt. The build output will be located in {builddir}/src/bin/svg2png/.

To use the svg2png converter you have to pass the SVG files parameter. It can be a file name with the .svg extension or a directory name. Multiple files or directories separated by a space are also accepted. If a directory is passed, the .svg file extension is searched inside it and in all of its subdirectories.

Optionally, the image resolution can be provided in the WxH format (two numbers separated by an x sign) following the -r flag.
The background color can be set with the -b flag. The bgColor parameter should be passed as a three-bytes hexadecimal value in the ffffff format. The default background is transparent.
Both flags, if provided, are applied to all of the .svg files.

The usage examples of the svg2png:

Usage:
    svg2png [SVG files] [-r resolution] [-b bgColor]

Flags:
    -r set the output image resolution.
    -b set the output image background color.

Examples:
    $ svg2png input.svg
    $ svg2png input.svg -r 200x200
    $ svg2png input.svg -r 200x200 -b ff00ff
    $ svg2png input1.svg input2.svg -r 200x200 -b ff00ff
    $ svg2png . -r 200x200

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SVG to TVG

ThorVG provides an executable svg2tvg converter that generates a TVG file from an SVG file.

To use svg2tvg, you must turn on this feature in the build option:

meson -Dtools=svg2tvg . build

Alternatively, you can add the svg2tvg value to the tools option in meson_option.txt. The build output will be located in {builddir}/src/bin/svg2tvg/.

Examples of the usage of the svg2tvg:

Usage:
   svg2tvg [SVG file]

Examples:
    $ svg2tvg input.svg

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API Bindings

Our main development APIs are written in C++, but ThorVG also provides API bindings for C.

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Issues or Feature Requests

For support, please reach us in Gitter.