Text Rendering using TrueType Font | C++

Rendering Text

In order to render text, the Rendering subsystem requires the implementation of Aspose.Font.Rendering.IGlyphOutlinePainter interface to draw glyph. This can be achieved using the following steps.

1. Implement the IGlyphOutlinePainter methods by creating a class GlyphOutlinePainter which requires object of type System.Drawing.Drawing2D.GraphicsPath for graphic drawing objectives. The implementation is as illustrated below.

   For complete examples and data files, please go to https://github.com/aspose-font/Aspose.Font-for-C
    RenderingText::GlyphOutlinePainter::GlyphOutlinePainter(System::SharedPtr<System::Drawing::Drawing2D::GraphicsPath> path)
    {
        _path = path;
    }
    
    void RenderingText::GlyphOutlinePainter::MoveTo(System::SharedPtr<Aspose::Font::RenderingPath::MoveTo> moveTo)
    {
        _path->CloseFigure();
        _currentPoint.set_X((float)moveTo->get_X());
        _currentPoint.set_Y((float)moveTo->get_Y());
    }
    
    void RenderingText::GlyphOutlinePainter::LineTo(System::SharedPtr<Aspose::Font::RenderingPath::LineTo> lineTo)
    {
        float x = (float)lineTo->get_X();
        float y = (float)lineTo->get_Y();
        _path->AddLine(_currentPoint.get_X(), _currentPoint.get_Y(), x, y);
        _currentPoint.set_X(x);
        _currentPoint.set_Y(y);
    }
    
    void RenderingText::GlyphOutlinePainter::CurveTo(System::SharedPtr<Aspose::Font::RenderingPath::CurveTo> curveTo)
    {
        float x3 = (float)curveTo->get_X3();
        float y3 = (float)curveTo->get_Y3();
        
        _path->AddBezier(_currentPoint.get_X(), _currentPoint.get_Y(), (float)curveTo->get_X1(), (float)curveTo->get_Y1(), (float)curveTo->get_X2(), (float)curveTo->get_Y2(), x3, y3);
        
        _currentPoint.set_X(x3);
        _currentPoint.set_Y(y3);
    }
    
    void RenderingText::GlyphOutlinePainter::ClosePath()
    {
        _path->CloseFigure();
    }
    
    System::Object::shared_members_type Aspose::Font::Examples::WorkingWithTrueTypeAndOpenTypeFonts::RenderingText::GlyphOutlinePainter::GetSharedMembers()
    {
        auto result = System::Object::GetSharedMembers();
        
        result.Add("Aspose::Font::Examples::WorkingWithTrueTypeAndOpenTypeFonts::RenderingText::GlyphOutlinePainter::_path", this->_path);
        result.Add("Aspose::Font::Examples::WorkingWithTrueTypeAndOpenTypeFonts::RenderingText::GlyphOutlinePainter::_currentPoint", this->_currentPoint);
        
        return result;
    }

2. Create method DrawText() which draws specified text into System.Drawing.Bitmap object and saves resultant bitmap on Disc. This will include the following steps:

• Iterate all symbols in text string.
• Get glyph identifier for every processed symbol - gid.
• Create object of type GlyphOutlinePainter which is required by rendering subsystem to draw current glyph.
• Create object of type Aspose.Font.Renderers.GlyphOutlineRenderer, and pass just created object of type GlyphOutlinePainter into constructor for GlyphOutlineRenderer. This object GlyphOutlineRenderer intended to render specified glyph.
• Render current processed glyph using method GlyphOutlineRenderer.RenderGlyph(). Aspose.Fonts.Matrix object is used to specify glyph coordinates. Glyph to render is specified by gid parameter.

Auxillary steps for this strategy

• Glyph coordinate for ‘Y’ axis is constant for this code snippet.
• Glyph coordinate for ‘X’ axis is calculated for every processed glyph.
• Both ‘X’ and ‘Y’ coordinates are passed into object Aspose.Fonts.Matrix which is used by GlyphOutlineRenderer to draw glyph.
• Distance between just processed and previous glyphs is calculated on every iteration step. This distance affects every glyph ‘X’ coordinate.
• Object of type GlyphOutlinePainter draws glyph with the help of GlyphOutlinePainter not into Bitmap directly, but into object GraphicsPath, which was passed into constructor for GlyphOutlinePainter, so we use object of type System.Drawing.Graphics to draw GraphicsPath into Bitmap.
• Method FontWidthToImageWith() which calculates glyph width for bitmap coordinate system.

Implementation of DrawText method is as shown below.

1. create utility method to calculate font width to image width as shown in the code sample below

   For complete examples and data files, please go to https://github.com/aspose-font/Aspose.Font-for-C
     double RenderingText::FontWidthToImageWith(double width, int32_t fontSourceResulution, double fontSize, double dpi /* = 300*/)
     {
         double resolutionCorrection = dpi / 72;
         // 72 is font's internal dpi
         return (width / fontSourceResulution) * fontSize * resolutionCorrection;
     }

Calling the Rendering Text functionality

To use the above implementations, the following sample code can be executed from the Main method of a console based application.

For complete examples and data files, please go to https://github.com/aspose-font/Aspose.Font-for-C
System::String dataDir = RunExamples::GetDataDir_Data();
    
System::String fileName1 = dataDir + u"Montserrat-Bold.ttf";
//Font file name with full path
System::SharedPtr<FontDefinition> fd1 = System::MakeObject<FontDefinition>(Aspose::Font::FontType::TTF, System::MakeObject<FontFileDefinition>(u"ttf", System::MakeObject<FileSystemStreamSource>(fileName1)));
System::SharedPtr<TtfFont> ttfFont1 = System::DynamicCast_noexcept<Aspose::Font::Ttf::TtfFont>(Aspose::Font::Font::Open(fd1));
    
System::String fileName2 = dataDir + u"Lora-Bold.ttf";
//Font file name with full path
System::SharedPtr<FontDefinition> fd2 = System::MakeObject<FontDefinition>(Aspose::Font::FontType::TTF, System::MakeObject<FontFileDefinition>(u"ttf", System::MakeObject<FileSystemStreamSource>(fileName2)));
System::SharedPtr<TtfFont> ttfFont2 = System::DynamicCast_noexcept<Aspose::Font::Ttf::TtfFont>(Aspose::Font::Font::Open(fd2));
    
DrawText(u"Hello world", ttfFont1, 14, System::Drawing::Brushes::get_White(), System::Drawing::Brushes::get_Black(), dataDir + u"hello1_montserrat_out.jpg");
DrawText(u"Hello world", ttfFont2, 14, System::Drawing::Brushes::get_Yellow(), System::Drawing::Brushes::get_Red(), dataDir + u"hello2_lora_out.jpg");