Manage PowerPoint Presentation Themes in Python

Overview

A presentation theme defines the properties of its design elements. When you select a theme, you’re choosing a coordinated set of visual elements and their properties.

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

theme-constituents

Change the Theme Color

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

This Python code shows how to change a theme’s accent color:

import aspose.pydrawing as draw
import aspose.slides as slides

with slides.Presentation() as presentation:
    slide = presentation.slides[0]

    shape = slide.shapes.add_auto_shape(slides.ShapeType.RECTANGLE, 10, 10, 100, 100)
    shape.fill_format.fill_type = slides.FillType.SOLID
    shape.fill_format.solid_fill_color.scheme_color = slides.SchemeColor.ACCENT4

You can determine the effective value of the resulting color as follows:

fill_effective = shape.fill_format.get_effective()
print("{0} ({1})".format(fill_effective.solid_fill_color.name, fill_effective.solid_fill_color))

# The example output:
#
# ff8064a2 (Color [A=255, R=128, G=100, B=162])

To further demonstrate the color change, we create another element, assign it the accent color from the initial step, and then update the theme color.

other_shape = slide.shapes.add_auto_shape(slides.ShapeType.RECTANGLE, 10, 120, 100, 100)
other_shape.fill_format.fill_type = slides.FillType.SOLID
other_shape.fill_format.solid_fill_color.scheme_color = slides.SchemeColor.ACCENT4

presentation.master_theme.color_scheme.accent4.color = draw.Color.red

The new color is applied automatically to both elements.

Set a Theme Color from the Additional Palette

When you apply luminance transformations to the main theme color (1), colors from the additional palette (2) are generated. You can then set and retrieve those theme colors.

additional-palette-colors

1 — Main theme colors

2 — Colors from the additional palette

This Python code demonstrates how additional-palette colors are derived from the main theme color and then used in shapes:

import aspose.slides as slides

with slides.Presentation() as presentation:
    slide = presentation.slides[0]

    # Accent 4
    shape1 = slide.shapes.add_auto_shape(slides.ShapeType.RECTANGLE, 10, 10, 50, 50)

    shape1.fill_format.fill_type = slides.FillType.SOLID
    shape1.fill_format.solid_fill_color.scheme_color = slides.SchemeColor.ACCENT4

    # Accent 4, Lighter 80%
    shape2 = slide.shapes.add_auto_shape(slides.ShapeType.RECTANGLE, 10, 70, 50, 50)

    shape2.fill_format.fill_type = slides.FillType.SOLID
    shape2.fill_format.solid_fill_color.scheme_color = slides.SchemeColor.ACCENT4
    shape2.fill_format.solid_fill_color.color_transform.add(slides.ColorTransformOperation.MULTIPLY_LUMINANCE, 0.2)
    shape2.fill_format.solid_fill_color.color_transform.add(slides.ColorTransformOperation.ADD_LUMINANCE, 0.8)

    # Accent 4, Lighter 60%
    shape3 = slide.shapes.add_auto_shape(slides.ShapeType.RECTANGLE, 10, 130, 50, 50)

    shape3.fill_format.fill_type = slides.FillType.SOLID
    shape3.fill_format.solid_fill_color.scheme_color = slides.SchemeColor.ACCENT4
    shape3.fill_format.solid_fill_color.color_transform.add(slides.ColorTransformOperation.MULTIPLY_LUMINANCE, 0.4)
    shape3.fill_format.solid_fill_color.color_transform.add(slides.ColorTransformOperation.ADD_LUMINANCE, 0.6)

    # Accent 4, Lighter 40%
    shape4 = slide.shapes.add_auto_shape(slides.ShapeType.RECTANGLE, 10, 190, 50, 50)

    shape4.fill_format.fill_type = slides.FillType.SOLID
    shape4.fill_format.solid_fill_color.scheme_color = slides.SchemeColor.ACCENT4
    shape4.fill_format.solid_fill_color.color_transform.add(slides.ColorTransformOperation.MULTIPLY_LUMINANCE, 0.6)
    shape4.fill_format.solid_fill_color.color_transform.add(slides.ColorTransformOperation.ADD_LUMINANCE, 0.4)

    # Accent 4, Darker 25%
    shape5 = slide.shapes.add_auto_shape(slides.ShapeType.RECTANGLE, 10, 250, 50, 50)

    shape5.fill_format.fill_type = slides.FillType.SOLID
    shape5.fill_format.solid_fill_color.scheme_color = slides.SchemeColor.ACCENT4
    shape5.fill_format.solid_fill_color.color_transform.add(slides.ColorTransformOperation.MULTIPLY_LUMINANCE, 0.75)

    # Accent 4, Darker 50%
    shape6 = slide.shapes.add_auto_shape(slides.ShapeType.RECTANGLE, 10, 310, 50, 50)

    shape6.fill_format.fill_type = slides.FillType.SOLID
    shape6.fill_format.solid_fill_color.scheme_color = slides.SchemeColor.ACCENT4
    shape6.fill_format.solid_fill_color.color_transform.add(slides.ColorTransformOperation.MULTIPLY_LUMINANCE, 0.5)

    presentation.save("example.pptx", slides.export.SaveFormat.PPTX)

Change the Theme Font

To allow you to select fonts for themes and other purposes, Aspose.Slides uses these special identifiers (similar to those 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 — Heading Font East Asian (Major East Asian Font)

This Python code shows how to assign the Latin font to a theme element:

portion = slides.Portion("Theme text format")
portion.portion_format.latin_font = slides.FontData("+mn-lt")

paragraph = slides.Paragraph()
paragraph.portions.add(portion)

shape = slide.shapes.add_auto_shape(slides.ShapeType.RECTANGLE, 10, 10, 100, 100)
shape.text_frame.paragraphs.add(paragraph)

This Python example shows how to change the presentation’s theme font:

presentation.master_theme.font_scheme.minor.latin_font = slides.FontData("Arial")

All text boxes will be updated to the new font.

TIP

For more information, see Master PowerPoint Fonts with Python.

Change the Theme Background Style

By default, PowerPoint provides 12 predefined backgrounds, but a typical presentation stores only 3 of them.

todo:image_alt_text

For example, after you save a presentation in PowerPoint, you can run the following Python code to determine how many predefined backgrounds it contains:

with slides.Presentation() as presentation:
    number_of_background_fills = len(presentation.master_theme.format_scheme.background_fill_styles)
    print(f"Number of theme background fill styles: {number_of_background_fills}")

Using the background_fill_styles property from the FormatScheme class, you can add or access background styles in a PowerPoint theme.

This Python example shows how to set the presentation background:

presentation.masters[0].background.style_index = 2  # 0 denotes no fill; indexing starts at 1.

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For more information, see Manage Presentation Backgrounds in Python.

Change the Theme Effects

A PowerPoint theme typically includes three values in each style array. These arrays combine into three effect levels: subtle, moderate, and intense. For example, here is the result when those effects are applied to a specific shape:

todo:image_alt_text

Using the three properties—FillStyles, LineStyles, and EffectStyles—from the FormatScheme class, you can modify theme elements (even more flexibly than in PowerPoint).

This Python code shows how to change a theme effect by altering parts of those elements:

with slides.Presentation("sample.pptx") as presentation:
    presentation.master_theme.format_scheme.line_styles[0].fill_format.solid_fill_color.color = draw.Color.red
    presentation.master_theme.format_scheme.fill_styles[2].fill_type = slides.FillType.SOLID
    presentation.master_theme.format_scheme.fill_styles[2].solid_fill_color.color = draw.Color.forest_green
    presentation.master_theme.format_scheme.effect_styles[2].effect_format.outer_shadow_effect.distance = 10

    presentation.save("output.pptx", slides.export.SaveFormat.PPTX)

The resulting changes include updates to the fill color, fill type, shadow effect, and other properties:

todo:image_alt_text

FAQ

Can I apply a theme to a single slide without changing the master?

Yes. Aspose.Slides support slide-level theme overrides, so you can apply a local theme to just that slide while keeping the master theme intact (via the SlideThemeManager).

What’s the safest way to carry a theme from one presentation to another?

Clone slides together with their master into the target presentation. This preserves the original master, layouts, and the associated theme so the appearance remains consistent.

How can I see the “effective” values after all inheritance and overrides?

Use the API’s “effective” views for theme/color/font/effect. These return the resolved, final properties after applying the master plus any local overrides.

Manage Presentation Backgrounds in Python