Working with Gradient in PostScript | C++

Add Gradient in PS Document

In this article, we consider the ways how a gradient can be used in PS documents.

The gradient is a smooth transition of one color to another. It is used for making the drawn pictures more realistic. As gradient is a kind of paint, it is expectedly that in C++ it is implemented as a subclass of System.Drawing.Brush. Actually, C++ platform has two such brushes:

• System.Drawing.LinearGradientBrush
• System.Drawing.PathGradientBrush

In order to set paint or a stroke in PsDocument we must pass an object of System.Drawing.Brush class for a painting and an object of System.Drawing.Pen for stroking into respective methods. Aspose.Page for C++ library processes all subclasses of System.Drawing.Brush that are offered by the C++ platform. These are System.Drawing.SolidBrush, System.Drawing.TextureBrush, System.Drawing.LinearGradientBrush, System.Drawing.PathGradientBrush and System.Drawing.HatchBrush. System.Drawing.Pen class cannot be extended because it is sealed, but it contains System.Drawing.Brush as a property and, thus, Aspose.Page for C++ library can also use a complete set of brushes also for drawing lines and outlining shapes and text.

In order to paint graphics objects with a gradient in Aspose.Page for C++ library it is necessary to create System.Drawing.LinearGradientBrush or System.Drawing.PathGradientBrush and pass it to SetPaint() or one of the FillText() or FillAndStrokeText() methods which accept System.Drawing.Brush as a parameter.

In order to outline graphics objects with a gradient in Aspose.Page for C++ library someone should create System.Drawing.LinearGradientBrush or System.Drawing.PathGradientBrush, then create System.Drawing.Pen with this brush and, finally, pass it to SetStroke() or one of the OutlineText() or FillAndStrokeText() methods which accepts System.Drawing.Pen as a parameter.

In the example below we demonstrate how to fill a shape and a text and outline the text with a gradient.

An algorithm for painting graphics objects with a gradient in a new PS document includes the following steps:

1. Create an output stream for the resulting PS file.
2. Create PsSaveOptions.
3. Create PsDocument with the already created output stream and save options.
4. Create the necessary graphics path or font in dependence on what object we are going to fill or outline.
5. Create an object of System.Drawing.LinearGradientBrush or System.Drawing.PathGradientBrush in dependence on the wishful form of a gradient.
6. Set the necessary transformation on this brush.
7. Set the gradient brush as the current paint in PsDocument
8. Fill the graphics path with current paint or fill a text. If we use one of the methods for filling the text that accepts System.Drawing.Brush as a parameter, the previous point can be ignored.
9. Close the page.
10. Save the document.

If we need stroking (outlining) graphics objects with a gradient instead of the last 4 points following will be:

8. Create the System.Drawing.Pen object with the gradient brush.

9. Set this pen as the current stroke in PsDocument.

10. Outline the graphics path with the current stroke or outline the text. If we use one of the methods for outlining the text that accepts System.Drawing.Pen as a parameter, previous point can be ignored.

11. Close the page.

12. Save the document.
    

We offer 5 code snippets that demonstrate a usage of different gradients.

In this code snippet we create horizontal linear gradient from two colors, fill a rectangle, fill a text, outline a text with this gradient.

    // The path to the documents directory.
    System::String dataDir = RunExamples::GetDataDir_WorkingWithGradient();
    
    //Create output stream for PostScript document
    {
        System::SharedPtr<System::IO::Stream> outPsStream = System::MakeObject<System::IO::FileStream>(dataDir + u"HorizontalGradient_outPS.ps", System::IO::FileMode::Create);
        // Clearing resources under 'using' statement
        System::Details::DisposeGuard<1> __dispose_guard_0({ outPsStream});
        // ------------------------------------------
        
        try
        {
            //Create save options with A4 size
            System::SharedPtr<PsSaveOptions> options = System::MakeObject<PsSaveOptions>();
            
            // Create new 1-paged PS Document
            System::SharedPtr<PsDocument> document = System::MakeObject<PsDocument>(outPsStream, options, false);
            
            float offsetX = 200.0f;
            float offsetY = 100.0f;
            float width = 200.0f;
            float height = 100.0f;
            
            //Create graphics path from the first rectangle
            System::SharedPtr<System::Drawing::Drawing2D::GraphicsPath> path = System::MakeObject<System::Drawing::Drawing2D::GraphicsPath>();
            path->AddRectangle(System::Drawing::RectangleF(offsetX, offsetY, width, height));
            
            //Create linear gradient brush with rectangle as a bounds, start and end colors
            System::SharedPtr<System::Drawing::Drawing2D::LinearGradientBrush> brush = System::MakeObject<System::Drawing::Drawing2D::LinearGradientBrush>(System::Drawing::RectangleF(0.0f, 0.0f, width, height), System::Drawing::Color::FromArgb(150, 0, 0, 0), System::Drawing::Color::FromArgb(50, 40, 128, 70), 0.f);
            //Create a transform for brush. X and Y scale component must be equal to width and height of the rectangle correspondingly.
            //Translation components are offsets of the rectangle
            System::SharedPtr<System::Drawing::Drawing2D::Matrix> brushTransform = System::MakeObject<System::Drawing::Drawing2D::Matrix>(width, 0.0f, 0.0f, height, offsetX, offsetY);
            //Set transform
            brush->set_Transform(brushTransform);
            
            //Set paint
            document->SetPaint(brush);
            
            //Fill the rectangle
            document->Fill(path);
            
            //Fill text with gradient
            System::SharedPtr<System::Drawing::Font> font = System::MakeObject<System::Drawing::Font>(u"Arial", 96.0f, System::Drawing::FontStyle::Bold);
            document->FillAndStrokeText(u"ABC", font, 200.0f, 300.0f, brush, System::MakeObject<System::Drawing::Pen>(System::MakeObject<System::Drawing::SolidBrush>(System::Drawing::Color::get_Black()), 2.0f));
            
            //Set current stroke
            document->SetStroke(System::MakeObject<System::Drawing::Pen>(brush, 5.0f));
            //Outline text with gradient
            document->OutlineText(u"ABC", font, 200.0f, 400.0f);
            
            //Close current page
            document->ClosePage();
            
            //Save the document
            document->Save();
        }
        catch(...)
        {
            __dispose_guard_0.SetCurrentException(std::current_exception());
        }
    }

The result of running this code is appeared as

In this code snippet we create a vertical linear gradient from 5 colors and fill a rectangle with this gradient.

    // The path to the documents directory.
    System::String dataDir = RunExamples::GetDataDir_WorkingWithGradient();
    
    //Create output stream for PostScript document
    {
        System::SharedPtr<System::IO::Stream> outPsStream = System::MakeObject<System::IO::FileStream>(dataDir + u"VerticalGradient_outPS.ps", System::IO::FileMode::Create);
        // Clearing resources under 'using' statement
        System::Details::DisposeGuard<1> __dispose_guard_0({ outPsStream});
        // ------------------------------------------
        
        try
        {
            //Create save options with A4 size
            System::SharedPtr<PsSaveOptions> options = System::MakeObject<PsSaveOptions>();
            
            // Create new 1-paged PS Document
            System::SharedPtr<PsDocument> document = System::MakeObject<PsDocument>(outPsStream, options, false);
            
            float offsetX = 200.0f;
            float offsetY = 100.0f;
            float width = 200.0f;
            float height = 100.0f;
            
            //Create graphics path from the first rectangle
            System::SharedPtr<System::Drawing::Drawing2D::GraphicsPath> path = System::MakeObject<System::Drawing::Drawing2D::GraphicsPath>();
            path->AddRectangle(System::Drawing::RectangleF(offsetX, offsetY, width, height));
            
            //Create an array of interpolation colors
            System::ArrayPtr<System::Drawing::Color> colors = System::MakeArray<System::Drawing::Color>({System::Drawing::Color::get_Red(), System::Drawing::Color::get_Green(), System::Drawing::Color::get_Blue(), System::Drawing::Color::get_Orange(), System::Drawing::Color::get_DarkOliveGreen()});
            System::ArrayPtr<float> positions = System::MakeArray<float>({0.0f, 0.1873f, 0.492f, 0.734f, 1.0f});
            System::SharedPtr<System::Drawing::Drawing2D::ColorBlend> colorBlend = System::MakeObject<System::Drawing::Drawing2D::ColorBlend>();
            colorBlend->set_Colors(colors);
            colorBlend->set_Positions(positions);
            
            //Create linear gradient brush with rectangle as a bounds, start and end colors
            System::SharedPtr<System::Drawing::Drawing2D::LinearGradientBrush> brush = System::MakeObject<System::Drawing::Drawing2D::LinearGradientBrush>(System::Drawing::RectangleF(0.0f, 0.0f, width, height), System::Drawing::Color::get_Beige(), System::Drawing::Color::get_DodgerBlue(), 0.f);
            //Set interpolation colors
            brush->set_InterpolationColors(colorBlend);
            //Create a transform for brush. X and Y scale component must be equal to width and height of the rectangle correspondingly.
            //Translation components are offsets of the rectangle
            System::SharedPtr<System::Drawing::Drawing2D::Matrix> brushTransform = System::MakeObject<System::Drawing::Drawing2D::Matrix>(width, 0.0f, 0.0f, height, offsetX, offsetY);
            //Rotate transform to get colors change in vertical direction from up to down
            brushTransform->Rotate(90.0f);
            //Set transform
            brush->set_Transform(brushTransform);
            
            //Set paint
            document->SetPaint(brush);
            
            //Fill the rectangle
            document->Fill(path);
            
            //Close current page
            document->ClosePage();
            
            //Save the document
            document->Save();
        }
        catch(...)
        {
            __dispose_guard_0.SetCurrentException(std::current_exception());
        }
    }

Here comes the result:

In this code snippet we create a diagonal linear gradient from 2 colors and fill a rectangle with this gradient.

    // The path to the documents directory.
    System::String dataDir = RunExamples::GetDataDir_WorkingWithGradient();
    
    //Create output stream for PostScript document
    {
        System::SharedPtr<System::IO::Stream> outPsStream = System::MakeObject<System::IO::FileStream>(dataDir + u"DiagonaGradient_outPS.ps", System::IO::FileMode::Create);
        // Clearing resources under 'using' statement
        System::Details::DisposeGuard<1> __dispose_guard_0({ outPsStream});
        // ------------------------------------------
        
        try
        {
            //Create save options with A4 size
            System::SharedPtr<PsSaveOptions> options = System::MakeObject<PsSaveOptions>();
            
            // Create new 1-paged PS Document
            System::SharedPtr<PsDocument> document = System::MakeObject<PsDocument>(outPsStream, options, false);
            
            float offsetX = 200.0f;
            float offsetY = 100.0f;
            float width = 200.0f;
            float height = 100.0f;
            
            //Create graphics path from the first rectangle
            System::SharedPtr<System::Drawing::Drawing2D::GraphicsPath> path = System::MakeObject<System::Drawing::Drawing2D::GraphicsPath>();
            path->AddRectangle(System::Drawing::RectangleF(offsetX, offsetY, width, height));
            
            //Create linear gradient brush with rectangle as a bounds, start and end colors
            System::SharedPtr<System::Drawing::Drawing2D::LinearGradientBrush> brush = System::MakeObject<System::Drawing::Drawing2D::LinearGradientBrush>(System::Drawing::RectangleF(0.0f, 0.0f, width, height), System::Drawing::Color::FromArgb(255, 255, 0, 0), System::Drawing::Color::FromArgb(255, 0, 0, 255), 0.f);
            
            //Create a transform for brush. X and Y scale component must be equal to width and height of the rectangle correspondingly.
            //Translation components are offsets of the rectangle                
            System::SharedPtr<System::Drawing::Drawing2D::Matrix> brushTransform = System::MakeObject<System::Drawing::Drawing2D::Matrix>(width, 0.0f, 0.0f, height, offsetX, offsetY);
            //Rotate gradient, than scale and translate to get visible color transition in required rectangle
            brushTransform->Rotate(-45.0f);
            float hypotenuse = (float)System::Math::Sqrt(200 * 200 + 100 * 100);
            float ratio = hypotenuse / 200;
            brushTransform->Scale(-ratio, 1.0f);
            brushTransform->Translate(100 / brushTransform->get_Elements()[0], 0.0f);
            
            //Set transform
            brush->set_Transform(brushTransform);
            
            //Set paint
            document->SetPaint(brush);
            
            //Fill the rectangle
            document->Fill(path);
            
            //Close current page
            document->ClosePage();
            
            //Save the document
            document->Save();
        }
        catch(...)
        {
            __dispose_guard_0.SetCurrentException(std::current_exception());
        }
    }

Here comes the result:

In this code snippet we create a radial gradient from 2 colors and fill a circle with this gradient.

    // The path to the documents directory.
    System::String dataDir = RunExamples::GetDataDir_WorkingWithGradient();
    
    //Create output stream for PostScript document
    {
        System::SharedPtr<System::IO::Stream> outPsStream = System::MakeObject<System::IO::FileStream>(dataDir + u"RadialGradient1_outPS.ps", System::IO::FileMode::Create);
        // Clearing resources under 'using' statement
        System::Details::DisposeGuard<1> __dispose_guard_0({ outPsStream});
        // ------------------------------------------
        
        try
        {
            //Create save options with A4 size
            System::SharedPtr<PsSaveOptions> options = System::MakeObject<PsSaveOptions>();
            
            // Create new 1-paged PS Document
            System::SharedPtr<PsDocument> document = System::MakeObject<PsDocument>(outPsStream, options, false);
            
            float offsetX = 200.0f;
            float offsetY = 100.0f;
            float width = 200.0f;
            float height = 200.0f;
            
            //Create graphics path from the rectangle bounds
            System::Drawing::RectangleF bounds(offsetX, offsetY, width, height);
            System::SharedPtr<System::Drawing::Drawing2D::GraphicsPath> path = System::MakeObject<System::Drawing::Drawing2D::GraphicsPath>();
            path->AddEllipse(bounds);
            
            //Create and fill color blend object
            System::ArrayPtr<System::Drawing::Color> colors = System::MakeArray<System::Drawing::Color>({System::Drawing::Color::get_White(), System::Drawing::Color::get_White(), System::Drawing::Color::get_Blue()});
            System::ArrayPtr<float> positions = System::MakeArray<float>({0.0f, 0.2f, 1.0f});
            System::SharedPtr<System::Drawing::Drawing2D::ColorBlend> colorBlend = System::MakeObject<System::Drawing::Drawing2D::ColorBlend>();
            colorBlend->set_Colors(colors);
            colorBlend->set_Positions(positions);
            
            System::SharedPtr<System::Drawing::Drawing2D::GraphicsPath> brushRect = System::MakeObject<System::Drawing::Drawing2D::GraphicsPath>();
            brushRect->AddRectangle(System::Drawing::RectangleF(0.0f, 0.0f, width, height));
            
            //Create path gradient brush with rectangle as a bounds
            System::SharedPtr<System::Drawing::Drawing2D::PathGradientBrush> brush = System::MakeObject<System::Drawing::Drawing2D::PathGradientBrush>(brushRect);
            //Set interpolation colors
            brush->set_InterpolationColors(colorBlend);
            //Create a transform for brush. X and Y scale component must be equal to width and height of the rectangle correspondingly.
            //Translation components are offsets of the rectangle
            System::SharedPtr<System::Drawing::Drawing2D::Matrix> brushTransform = System::MakeObject<System::Drawing::Drawing2D::Matrix>(width, 0.0f, 0.0f, height, offsetX, offsetY);
            //Set transform
            brush->set_Transform(brushTransform);
            
            //Set paint
            document->SetPaint(brush);
            
            //Fill the rectangle
            document->Fill(path);
            
            //Close current page
            document->ClosePage();
            
            //Save the document
            document->Save();
        }
        catch(...)
        {
            __dispose_guard_0.SetCurrentException(std::current_exception());
        }
    }
}

The result

In this code snippet we create a radial gradient from 6 colors and fill a rectangle with this gradient.

    // The path to the documents directory.
    System::String dataDir = RunExamples::GetDataDir_WorkingWithGradient();
    
    //Create output stream for PostScript document
    {
        System::SharedPtr<System::IO::Stream> outPsStream = System::MakeObject<System::IO::FileStream>(dataDir + u"RadialGradient2_outPS.ps", System::IO::FileMode::Create);
        // Clearing resources under 'using' statement
        System::Details::DisposeGuard<1> __dispose_guard_0({ outPsStream});
        // ------------------------------------------
        
        try
        {
            //Create save options with A4 size
            System::SharedPtr<PsSaveOptions> options = System::MakeObject<PsSaveOptions>();
            
            // Create new 1-paged PS Document
            System::SharedPtr<PsDocument> document = System::MakeObject<PsDocument>(outPsStream, options, false);
            
            float offsetX = 200.0f;
            float offsetY = 100.0f;
            float width = 200.0f;
            float height = 200.0f;
            
            //Create graphics path from the rectangle bounds
            System::Drawing::RectangleF bounds(offsetX, offsetY, width, height);
            System::SharedPtr<System::Drawing::Drawing2D::GraphicsPath> path = System::MakeObject<System::Drawing::Drawing2D::GraphicsPath>();
            path->AddRectangle(bounds);
            
            //Create and fill color blend object
            System::ArrayPtr<System::Drawing::Color> colors = System::MakeArray<System::Drawing::Color>({System::Drawing::Color::get_Green(), System::Drawing::Color::get_Blue(), System::Drawing::Color::get_Black(), System::Drawing::Color::get_Yellow(), System::Drawing::Color::get_Beige(), System::Drawing::Color::get_Red()});
            System::ArrayPtr<float> positions = System::MakeArray<float>({0.0f, 0.2f, 0.3f, 0.4f, 0.9f, 1.0f});
            System::SharedPtr<System::Drawing::Drawing2D::ColorBlend> colorBlend = System::MakeObject<System::Drawing::Drawing2D::ColorBlend>();
            colorBlend->set_Colors(colors);
            colorBlend->set_Positions(positions);
            
            System::SharedPtr<System::Drawing::Drawing2D::GraphicsPath> brushRect = System::MakeObject<System::Drawing::Drawing2D::GraphicsPath>();
            brushRect->AddRectangle(System::Drawing::RectangleF(0.0f, 0.0f, width, height));
            
            //Create path gradient brush with rectangle as a bounds
            System::SharedPtr<System::Drawing::Drawing2D::PathGradientBrush> brush = System::MakeObject<System::Drawing::Drawing2D::PathGradientBrush>(brushRect);
            //Set interpolation colors
            brush->set_InterpolationColors(colorBlend);
            //Create a transform for brush. X and Y scale component must be equal to width and height of the rectangle correspondingly.
            //Translation components are offsets of the rectangle
            System::SharedPtr<System::Drawing::Drawing2D::Matrix> brushTransform = System::MakeObject<System::Drawing::Drawing2D::Matrix>(width, 0.0f, 0.0f, height, offsetX, offsetY);
            //Set transform
            brush->set_Transform(brushTransform);
            
            //Set paint
            document->SetPaint(brush);
            
            //Fill the rectangle
            document->Fill(path);
            
            //Close current page
            document->ClosePage();
            
            //Save the document
            document->Save();
        }
        catch(...)
        {
            __dispose_guard_0.SetCurrentException(std::current_exception());
        }
    }
}

The result

See working with gradient in PS documents in .NET or Java.

You can download examples and data files from GitHub.