Presentation Theme

A presentation theme defines the properties of design elements. When you select a presentation theme, you are essentially choosing a specific set of visual elements and their properties.

In PowerPoint, a theme comprises colors, fonts, background styles, and effects.

theme-constituents

Change Theme Color

A PowerPoint theme uses a specific set of colors for different elements on a slide. If you don’t like the colors, you change them colors by applying new colors for the theme. To allow you select a new theme color, Aspose.Slides provides values under the SchemeColor enumeration.

This C# code shows you how to change the accent color for a theme:

using (Presentation pres = new Presentation())
    
{
    IAutoShape shape = pres.Slides[0].Shapes.AddAutoShape(ShapeType.Rectangle, 10, 10, 100, 100);

    shape.FillFormat.FillType = FillType.Solid;

    shape.FillFormat.SolidFillColor.SchemeColor = SchemeColor.Accent4;
}

You can determine the resulting color’s effective value this way:

var fillEffective = shape.FillFormat.GetEffective();

Console.WriteLine($"{fillEffective.SolidFillColor.Name} ({fillEffective.SolidFillColor})"); // ff8064a2 (Color [A=255, R=128, G=100, B=162])

To further demonstrate the color change operation, we create another element and assign the accent color (from the initial operation) to it. Then we change the color in the theme:

IAutoShape otherShape = pres.Slides[0].Shapes.AddAutoShape(ShapeType.Rectangle, 10, 120, 100, 100);

otherShape.FillFormat.FillType = FillType.Solid;

otherShape.FillFormat.SolidFillColor.SchemeColor = SchemeColor.Accent4;

pres.MasterTheme.ColorScheme.Accent4.Color = Color.Red;

The new color is applied automatically on both elements.

Set Theme Color from Additional Palette

When you apply luminance transformations to the main color, colors from the additional palette are formed. You can then set and get those theme colors.

additional-palette-colors

1- Main theme colors

2 - Colors from the additional palette.

This C# code demonstrates an operation where additional palette colors are obtained from the main theme color and then used in shapes:

using (Presentation presentation = new Presentation())
{
    ISlide slide = presentation.Slides[0];

    // Accent 4
    IShape shape1 = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 10, 10, 50, 50);

    shape1.FillFormat.FillType = FillType.Solid;
    shape1.FillFormat.SolidFillColor.SchemeColor = SchemeColor.Accent4;

    // Accent 4, Lighter 80%
    IShape shape2 = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 10, 70, 50, 50);

    shape2.FillFormat.FillType = FillType.Solid;
    shape2.FillFormat.SolidFillColor.SchemeColor = SchemeColor.Accent4;
    shape2.FillFormat.SolidFillColor.ColorTransform.Add(ColorTransformOperation.MultiplyLuminance, 0.2f);
    shape2.FillFormat.SolidFillColor.ColorTransform.Add(ColorTransformOperation.AddLuminance, 0.8f);

    // Accent 4, Lighter 60%
    IShape shape3 = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 10, 130, 50, 50);

    shape3.FillFormat.FillType = FillType.Solid;
    shape3.FillFormat.SolidFillColor.SchemeColor = SchemeColor.Accent4;
    shape3.FillFormat.SolidFillColor.ColorTransform.Add(ColorTransformOperation.MultiplyLuminance, 0.4f);
    shape3.FillFormat.SolidFillColor.ColorTransform.Add(ColorTransformOperation.AddLuminance, 0.6f);

    // Accent 4, Lighter 40%
    IShape shape4 = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 10, 190, 50, 50);

    shape4.FillFormat.FillType = FillType.Solid;
    shape4.FillFormat.SolidFillColor.SchemeColor = SchemeColor.Accent4;
    shape4.FillFormat.SolidFillColor.ColorTransform.Add(ColorTransformOperation.MultiplyLuminance, 0.6f);
    shape4.FillFormat.SolidFillColor.ColorTransform.Add(ColorTransformOperation.AddLuminance, 0.4f);

    // Accent 4, Darker 25%
    IShape shape5 = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 10, 250, 50, 50);

    shape5.FillFormat.FillType = FillType.Solid;
    shape5.FillFormat.SolidFillColor.SchemeColor = SchemeColor.Accent4;
    shape5.FillFormat.SolidFillColor.ColorTransform.Add(ColorTransformOperation.MultiplyLuminance, 0.75f);

    // Accent 4, Darker 50%
    IShape shape6 = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 10, 310, 50, 50);

    shape6.FillFormat.FillType = FillType.Solid;
    shape6.FillFormat.SolidFillColor.SchemeColor = SchemeColor.Accent4;
    shape6.FillFormat.SolidFillColor.ColorTransform.Add(ColorTransformOperation.MultiplyLuminance, 0.5f);

    presentation.Save("example.pptx", SaveFormat.Pptx);
}

Change Theme Font

To allow you select fonts for themes and other purposes, Aspose.Slides uses these special identifiers (similar to those used in PowerPoint):

  • +mn-lt - Body Font Latin (Minor Latin Font)
  • +mj-lt -Heading Font Latin (Major Latin Font)
  • +mn-ea - Body Font East Asian (Minor East Asian Font)
  • +mj-ea - Body Font East Asian (Minor East Asian Font)

This C# code shows you how to assign the Latin font to a theme element:

IAutoShape shape = pres.Slides[0].Shapes.AddAutoShape(ShapeType.Rectangle, 10, 10, 100, 100);

Paragraph paragraph = new Paragraph();

Portion portion = new Portion("Theme text format");

paragraph.Portions.Add(portion);

shape.TextFrame.Paragraphs.Add(paragraph);

portion.PortionFormat.LatinFont = new FontData("+mn-lt");

This C# code shows you how to change the presentation theme font:

pres.MasterTheme.FontScheme.Minor.LatinFont = new FontData("Arial");

The font in all text boxes will be updated.

Change Theme Background Style

By default, the PowerPoint app provides 12 predefined backgrounds but only 3 from those 12 backgrounds are saved in a typical presentation.

todo:image_alt_text

For example, after you save a presentation in the PowerPoint app, you can run this C# code to find out the number predefined backgrounds in the presentation:

using (Presentation pres = new Presentation("pres.pptx"))

{
    int numberOfBackgroundFills = pres.MasterTheme.FormatScheme.BackgroundFillStyles.Count;

    Console.WriteLine($"Number of background fill styles for theme is {numberOfBackgroundFills}");
}

This C# code shows you how to set the background for a presentation:

pres.Masters[0].Background.StyleIndex = 2;

Index guide: 0 is used for no fill. The index starts from 1.

Change Theme Effect

A PowerPoint theme usually contains 3 values for each style array. Those arrays are combined into these 3 effects: subtle, moderate, and intense. For example, this is the outcome when the effects are applied to a specific shape:

todo:image_alt_text

Using 3 properties (FillStyles, LineStyles, EffectStyles) from the FormatScheme class you can change the elements in a theme (even more flexibly than the options in PowerPoint).

This C# code shows you how to change a theme effect by altering parts of elements:

using (Presentation pres = new Presentation("Subtle_Moderate_Intense.pptx"))
{
    pres.MasterTheme.FormatScheme.LineStyles[0].FillFormat.SolidFillColor.Color = Color.Red;

    pres.MasterTheme.FormatScheme.FillStyles[2].FillType = FillType.Solid;

    pres.MasterTheme.FormatScheme.FillStyles[2].SolidFillColor.Color = Color.ForestGreen;

    pres.MasterTheme.FormatScheme.EffectStyles[2].EffectFormat.OuterShadowEffect.Distance = 10f;

    pres.Save("Design_04_Subtle_Moderate_Intense-out.pptx", SaveFormat.Pptx);
}

The resulting changes in fill color, fill type, shadow effect, etc:

todo:image_alt_text