powerpoint

PowerPoint Skill

Generates, updates, and manages PowerPoint slide decks using python-pptx with YAML-driven content and styling definitions.

Overview

This skill provides Python scripts that consume YAML configuration files to produce PowerPoint slide decks. Each slide is defined by a content.yaml file describing its layout, text, and shapes. A style.yaml file defines dimensions, template configuration, layout mappings, metadata, and defaults.

SKILL.md covers technical reference: prerequisites, commands, script architecture, API constraints, and troubleshooting. For conventions and design rules (element positioning, visual quality, color and contrast, contextual styling), follow pptx.instructions.md.

Prerequisites

PowerShell

The Invoke-PptxPipeline.ps1 script handles virtual environment creation and dependency installation automatically via uv sync. Requires uv, Python 3.11+, and PowerShell 7+.

Installing uv

If uv is not installed:

# macOS / Linux
curl -LsSf https://astral.sh/uv/install.sh | sh
 
# Windows
powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"
 
# Via pip (fallback)
pip install uv

System Dependencies (Export and Validation)

The Export and Validate actions require LibreOffice for PPTX-to-PDF conversion and optionally pdftoppm from poppler for PDF-to-JPG rendering. When pdftoppm is not available, PyMuPDF handles the image rendering.

The Validate action's vision-based checks require the GitHub Copilot CLI for model access.

Copilot CLI (Vision Validation)

The validate_slides.py script uses the GitHub Copilot SDK to send slide images to vision-capable models. The Copilot CLI must be installed and authenticated:

Required Files

• style.yaml — Dimensions, defaults, template configuration, and metadata
• content.yaml — Per-slide content definition (text, shapes, images, layout)
• (Optional) content-extra.py — Custom Python for complex slide drawings

Content Directory Structure

All slide content lives under the working directory's content/ folder:

Global Style Definition (style.yaml)

The global style.yaml defines dimensions, template configuration, layout mappings, metadata, and defaults. Color and font choices are specified per-element in each slide's content.yaml rather than centralized in the style file.

See the style.yaml template for the full template, field reference, and usage instructions.

Per-Slide Content Definition (content.yaml)

Each slide's content.yaml defines layout, text, shapes, and positioning. All position and size values are in inches. Color values use #RRGGBB hex format or @theme_name references.

Text contract: markdown-like list lines in textbox.text and shape.text are interpreted as PowerPoint lists during rendering. Unordered markers (-, +, *) become bulleted paragraphs, ordered markers (1., 1)) become auto-numbered paragraphs, and leading indentation maps to paragraph level.

See the content.yaml template for the full template, supported element types, supported shape types, and usage instructions.

Complex Drawings (content-extra.py)

When a slide requires complex drawings that cannot be expressed through content.yaml element definitions, create a content-extra.py file in the slide folder. The render() function signature is fixed. The build script calls it after placing standard content.yaml elements.

See the content-extra.py template for the full template, function parameters, and usage guidelines.

Security Validation

Before executing a content-extra.py file, the build script performs AST-based static analysis to reject dangerous code. Validation runs automatically unless the --allow-scripts flag is passed.

Allowed imports:

• pptx and all pptx.* submodules
• Safe standard-library modules (e.g., math, copy, json, re, pathlib, collections, itertools, functools, typing, enum, dataclasses, decimal, fractions, string, textwrap)

Blocked imports:

• subprocess, os, shutil, socket, ctypes, signal, multiprocessing, threading, http, urllib, ftplib, smtplib, imaplib, poplib, xmlrpc, webbrowser, code, codeop, compileall, py_compile, zipimport, pkgutil, runpy, ensurepip, venv, sqlite3, tempfile, shelve, dbm, pickle, marshal, importlib, sys, telnetlib
• Any third-party package not on the allowlist

Blocked builtins:

• Dangerous: eval, exec, __import__, compile, breakpoint
• Indirect bypass: getattr, setattr, delattr, globals, locals, vars

Runtime namespace restriction:

Even after AST validation passes, the executed module runs in a restricted namespace where __builtins__ is limited to safe builtins only. The dangerous and indirect-bypass builtins listed above are removed from the module namespace before execution (__import__ is kept because the import machinery requires it; the AST checker blocks direct __import__() calls).

--allow-scripts flag:

Pass --allow-scripts to skip AST validation and namespace restriction for trusted content. This flag is required when a content-extra.py script legitimately needs blocked imports or builtins.

When validation fails, the build raises ContentExtraError with a message identifying the violation and file path.

Script Reference

All operations are available through the PowerShell orchestrator (Invoke-PptxPipeline.ps1) or directly via the Python scripts. The PowerShell script manages the Python virtual environment and dependency installation automatically via uv sync.

Build a Slide Deck

Reads all content/slide-*/content.yaml files in numeric order and generates the complete deck. Executes content-extra.py files when present.

Build from a Template

[!WARNING] --template creates a NEW presentation inheriting only slide masters, layouts, and theme from the template. All existing slides are discarded. Use --source for partial rebuilds.

Loads slide masters and layouts from the template PPTX. Layout names in each slide's content.yaml resolve against the template's layouts, with optional name mapping via the layouts section in style.yaml. Populate themed layout placeholders using the placeholders section in content YAML.

Update Specific Slides

[!IMPORTANT] Use --source (not --template) for partial rebuilds. Combining --template and --source is not supported.

Opens the existing deck, clears shapes on the specified slides, rebuilds them in-place from their content.yaml, and saves. All other slides remain untouched. After building, verify the output slide count matches the original deck.

Extract Content from Existing PPTX

Extracts text, shapes, images, and styling from an existing PPTX into the content/ folder structure. Creates content.yaml files for each slide and populates the global/style.yaml from detected patterns.

Extract Specific Slides

Extracts only the specified slides (plus the global style). Useful for targeted updates on large decks.

Extraction Limitations

• Picture shapes that reference external (linked) images instead of embedded blobs are recorded with path: LINKED_IMAGE_NOT_EMBEDDED. The script does not crash but the image must be re-embedded manually.
• When text elements inherit font, size, or color from the slide master or layout, the extraction records no inline styling. Content YAML for these elements needs explicit font properties added before rebuild.
• The detect_global_style() function uses frequency analysis across all slides. For decks with mixed styling, review and adjust style.yaml values manually after extraction.

Validate a Deck

The Validate action runs a two- or three-step pipeline:

1. Export — Clears stale slide images from the output directory, then renders slides to JPG images via LibreOffice (PPTX → PDF → JPG). When -Slides is used, output images are named to match original slide numbers (e.g., slide-023.jpg for slide 23), not sequential PDF page numbers.
2. PPTX validation — Checks PPTX-only properties (validate_deck.py) for speaker notes and slide count.
3. Vision validation (optional) — Sends slide images to a vision-capable model via the Copilot SDK (validate_slides.py) for visual quality checks. Runs when -ValidationPrompt or -ValidationPromptFile is provided.

For validation criteria (element positioning, visual quality, color contrast, content completeness), see pptx.instructions.md Validation Criteria.

Built-in System Message

The validate_slides.py script includes a built-in system message that focuses on issue detection only (not full slide description). It checks overlapping elements, text overflow/cutoff, decorative line mismatch after title wraps, citation/footer collisions, tight spacing, uneven gaps, insufficient edge margins, alignment inconsistencies, low contrast, narrow text boxes, and leftover placeholders. For dense slides, near-edge placement or tight boundaries are acceptable when readability is not materially affected. The -ValidationPrompt parameter provides supplementary user-level context and does not need to repeat these checks.

Validate with Vision Checks

Vision validation results are written to validation-results.json in the image output directory, containing raw model responses per slide with quality findings. Per-slide response text is also written to slide-NNN-validation.txt files next to each slide image.

Validate Specific Slides

Validates only the specified slides. When content directories cover fewer slides than the PPTX, the slide count check reports an informational note rather than an error.

validate_slides.py CLI Reference

validate_deck.py CLI Reference

Validation Outputs

When run through the pipeline, validation produces these files in the image output directory:

Per-slide vision text files are written alongside their corresponding slide-NNN.jpg images, enabling agents to read validation findings for individual slides without parsing the consolidated JSON file.

Validation Scope for Changed Slides

When validating after modifying or adding specific slides, always validate a block that includes one slide before and one slide after the changed or added slides. This catches edge-proximity issues, transition inconsistencies, and spacing problems that arise between adjacent slides.

For example, when slides 5 and 6 were changed, validate slides 4 through 7:

Export Slides to Images

Converts specified slides to JPG images for visual inspection. The PowerShell orchestrator handles both steps automatically, clears stale images before exporting, names output images to match original slide numbers when -Slides is used, and uses a PyMuPDF fallback when pdftoppm is not installed.

When running the two-step process manually (outside the pipeline), note that render_pdf_images.py uses sequential numbering by default. Pass --slide-numbers to map output images to original slide positions:

Dependencies: Requires LibreOffice for PPTX-to-PDF conversion and either pdftoppm (from poppler) or pymupdf (pip) for PDF-to-JPG rendering.

Dry-Run Validation

Validates content files without producing a PPTX. Parses all content.yaml files, checks for speaker notes, runs AST validation on content-extra.py scripts, and counts image assets. Exit codes:

• code 0: no errors found
• code 1: one or more slide-level content errors (YAML parse failures, invalid scripts)
• code 2: configuration error (e.g., no slide content found in the content directory)

Generate Theme Variants

Generates themed content directories from a base content directory using a color mapping YAML file. The themes YAML defines color replacement tables:

Each theme gets its own output directory with remapped content.yaml, style.yaml, and content-extra.py files. Images are copied as-is. Run build_deck.py on each themed directory to produce the PPTX.

Embed Audio

Embeds WAV audio files into PPTX slides. Audio files are matched to slides by naming convention (slide-001.wav, slide-002.wav, etc.). The audio icon is placed off-screen (below the slide boundary) to keep it hidden during presentation. Pass --slides to embed audio on specific slides only.

Dependencies: Requires pillow (pip install pillow) for poster frame generation.

[!NOTE] WAV files are embedded uncompressed. For large narrated decks, consider pre-compressing audio before embedding to manage PPTX file size.

Export Slides to SVG

Exports slides to SVG format via LibreOffice (PPTX → PDF) and PyMuPDF (PDF → SVG). Output files are named slide-NNN.svg. Pass --slides to export specific slides. Dependencies: Requires LibreOffice and pymupdf.

Script Architecture

The build and extraction scripts use shared modules in the scripts/ directory:

python-pptx Constraints

• python-pptx does NOT support SVG images. Always convert to PNG via cairosvg or Pillow.
• python-pptx cannot create new slide masters or layouts programmatically. Use blank layouts or start from a template PPTX with the --template argument.
• Transitions and animations are preserved when opening and saving existing files, but cannot be created or modified via the API.
• When extracting content, slide master and layout inheritance means many text elements have no inline styling. Add explicit font properties in content YAML before rebuilding.
• The Export and Validate actions require LibreOffice for PPTX-to-PDF conversion. The PowerShell orchestrator checks for LibreOffice availability before starting and provides platform-specific install instructions if missing.
• Accessing background.fill on slides with inherited backgrounds replaces them with NoFill. Check slide.follow_master_background before accessing the fill property.
• Gradient fills use the python-pptx GradientFill API with GradientStop objects. Each stop specifies a position (0–100) and a color.
• Theme colors resolve via MSO_THEME_COLOR enum. Brightness adjustments apply through the color format's brightness property.
• Template-based builds load layouts by name or index. Layout name resolution falls back to index 6 (blank) when no match is found.

Security Considerations

This skill processes PDF files via PyMuPDF, which wraps the MuPDF C library. MuPDF parses untrusted binary structures (cross-reference tables, stream objects, font definitions) and historical CVEs have shown that memory-safety bugs in C parsers can lead to crashes, memory disclosure, or in rare cases code execution.

Mitigations in place

• scripts/pdf_safety.py validates every PDF (existence, regular-file, size <= 100 MB, %PDF- magic bytes, page count <= 1000) before calling fitz.open().
• All fitz operations are wrapped in safe_open_pdf(), which converts MuPDF exceptions into typed PdfSafetyError subclasses (PdfTooLargeError, PdfInvalidFormatError, PdfTooManyPagesError, PdfParseError, PdfRenderError).
• pymupdf is version-pinned in pyproject.toml (>=1.27.1,<2.0) to track security fixes without silently adopting a major-version API change.

Defense-in-depth note: the 5-byte %PDF- magic check is a necessary but not sufficient guarantee of structural validity. A crafted small file that begins with %PDF- still reaches the MuPDF parser, where memory-safety bugs may exist. Callers MUST keep PyMuPDF patched against the latest advisories (tracked via microsoft/hve-core#1020 / pip-audit) and continue to treat such inputs as untrusted. The PdfSafetyError hierarchy (PdfTooLargeError, PdfInvalidFormatError, PdfTooManyPagesError, PdfParseError, PdfRenderError) is one defense layer alongside the version pin and CVE monitoring; no single layer is sufficient on its own.

Accepted risk

These mitigations reduce but do not eliminate the C-extension attack surface. Consumers SHOULD treat PDF inputs from outside this skill's PPTX-to-PDF pipeline as untrusted and apply additional sandboxing (subprocess, container) before feeding adversarial input.

Update policy

Re-check NVD and OSV advisories for MuPDF and PyMuPDF quarterly and on every pip-audit alert.

Cross-references

• microsoft/hve-core#1018 — original hardening request
• microsoft/hve-core#1020 — pip-audit CI for ongoing CVE monitoring (separate effort)

Troubleshooting

Environment Recovery

When scripts fail due to missing modules, import errors, or a corrupt virtual environment, recover with:

This recreates the virtual environment from scratch using pyproject.toml as the single source of truth. The Invoke-PptxPipeline.ps1 orchestrator runs uv sync automatically on each invocation unless -SkipVenvSetup is passed.

When uv itself is not available, install it first (see Installing uv above), then retry. When Python 3.11+ is not available, run uv python install 3.11 to have uv fetch and manage the interpreter.