Powerpoint

Powerpoint Skill

Create, read, and edit PowerPoint decks — from-scratch generation with pptxgenjs, template-based editing via direct XML manipulation, speaker notes, charts, and design QA. A .pptx is a ZIP archive of XML files.

When to Use

Use this skill any time a .pptx or .potx file is involved in any way — as input, output, or both: creating slide decks, pitch decks, or presentations; reading or extracting text from any .pptx; editing existing presentations; combining or splitting slide files; working with templates (.potx), layouts, speaker notes, or comments. Trigger whenever the user mentions "deck," "slides," "presentation," or references a .pptx/.potx filename.

Prerequisites

npm ls pptxgenjs --depth=0 2>/dev/null | grep -q pptxgenjs || npm install pptxgenjs
pip install "markitdown[pptx]" Pillow defusedxml lxml
which soffice || sudo apt install -y libreoffice     # rendering/QA
which pdftoppm || sudo apt install -y poppler-utils  # PDF → images

macOS: brew install libreoffice poppler. Icons in generated decks additionally use react-icons react react-dom sharp (npm).

Quick Reference

Scripts

Paths are relative to this skill's directory. Everything else is plain Python, node, or shell.

Creating with pptxgenjs — gotchas

Write the script and require('pptxgenjs'). The model knows the API; these are the footguns:

• Set pres.layout before adding slides. The default canvas is LAYOUT_16x9 = 10" × 5.625", not 13.3" wide. Coordinates past the edge are written, not clamped — the shape just isn't on the slide. (LAYOUT_WIDE is 13.3" × 7.5".)
• Hex colors: never #, never 8 digits. color: "FF0000". Both "#FF0000" and alpha baked into the hex ("00000020") corrupt the file. For translucency: transparency: 0-100 on fills and images, opacity: 0.0-1.0 on shadows — each is silently ignored on the other.
• pptxgenjs mutates option objects in place (converts values to EMU on first use). Never share one shadow/options object across two add* calls — build a fresh object each time.
• Shadow offset must be ≥ 0 — a negative offset corrupts the file. To cast a shadow upward, use angle: 270 with a positive offset.
• letterSpacing is silently ignored — the real option is charSpacing.
• Lists: bullet: true on each item, never a literal • (renders double bullets). Set breakLine: true on every array item except the last. Space bulleted paragraphs with paraSpaceAfter, not lineSpacing (huge gaps).
• One new pptxgen() per output file — never reuse an instance.
• rectRadius only works on ROUNDED_RECTANGLE, not RECTANGLE.
• Gradient fills aren't supported — use a gradient image as the background instead.
• Text boxes have built-in internal padding — set margin: 0 whenever text must align with a shape, line, or icon at the same x.
• Speaker notes go in slide.addNotes("...") (plain text, once per slide), never in a text box on the slide.
• Keep charts native. Use addChart() for everything PowerPoint can chart (pass an array of {type, data, options} for combos). For PowerPoint-native features the library doesn't expose (trendlines, error bars), compute the extra series yourself or post-process the generated OOXML — do not fall back to a rendered image. Only chart types PowerPoint has no native form for (Sankey, network, chord) go in as images.
• Default charts render bare — no title, no data labels, dated palette. Set showTitle + title, showValue: true + dataLabelPosition, chartColors: [...] from your palette, and quiet the frame (catAxisLabelColor/valAxisLabelColor, valGridLine: { color, size }, catGridLine: { style: "none" }, showLegend: false for a single series).
• On a stacked bar or column chart, dataLabelPosition must be ctr, inEnd, or inBase. outEnd corrupts the file.
• A combo series using secondaryValAxis/secondaryCatAxis needs both valAxes and catAxes on the chart options, two entries each. Without them pptxgenjs writes axis ids it never declares, and PowerPoint discards that chart and reports the file as corrupt. Supplying only valAxes is not enough.
• After writeFile(), run python scripts/office/validate.py deck.pptx. It reports the two chart faults above and the slide-XML defects PowerPoint refuses, and names the fix for each. Fix them in your generator, not by hand-editing the packed XML.
• Never reorder the children of <p:presentation>. pptxgenjs writes <p:notesMasterIdLst> right after <p:sldIdLst> and points both masters at one theme part. PowerPoint reads that happily — move the element and the same deck becomes unopenable.
• Icons: render react-icons to SVG (ReactDOMServer.renderToStaticMarkup), rasterize with sharp at ≥256px, and insert via addImage({ data: "image/png;base64," + buf.toString("base64") }) — the image/png;base64, prefix is required.

Editing existing decks and templates

Pick layouts first: python scripts/thumbnail.py template.pptx template-thumbs writes a labeled grid of every slide and prints the file(s) it created — template-thumbs.jpg, split into template-thumbs-N.jpg past 12 slides. Always pass that second argument, named after the deck. It defaults to thumbnails, so two decks thumbnailed in one directory silently overwrite each other's grids (template analysis only — visual QA needs the full-resolution renders from Converting to Images; it only accepts .pptx, so copy a .potx to a .pptx name first). Use it with markitdown to map each content section onto a template slide, and vary the layouts — don't put every section on the same title-and-bullets slide.

python3 -c "import sys,zipfile; zipfile.ZipFile(sys.argv[1]).extractall('unpacked')" deck.pptx
python scripts/add_slide.py unpacked/ slide2.xml --after slide2.xml   # duplicate a slide (or slideLayoutN.xml); prints the new slide's path
# reorder / delete slides = edit <p:sldIdLst> in ppt/presentation.xml
python scripts/clean.py unpacked/                                     # after deletions: removes orphaned slides, media, rels
# edit slide content in ppt/slides/slideN.xml
(cd unpacked && rm -f ../out.pptx && zip -Xr ../out.pptx .)           # zip from INSIDE the dir; rm first or deleted parts survive
python scripts/office/validate.py out.pptx --original deck.pptx

• Do all structural work — add, delete, reorder — before editing any slide's content. add_slide.py copies a slide file verbatim, so duplicating after you edit clones the edited content; and clean.py deletes any slide missing from <p:sldIdLst>, including one you just wrote.
• Never copy a slide file by hand — add_slide.py does every registration a new slide needs and reports what it made. It also works directly on a file: add_slide.py deck.pptx slide2.xml -o out.pptx — pass -o, or it rewrites the input deck in place. A duplicated slide still references its source's chart/SmartArt/embedded-object parts rather than cloning them, so editing one slide's chart changes the other's.
• If you use python-pptx, three things it won't do: duplicate a slide (its only entry point is add_slide(layout)), preserve formatting through text_frame.text = "..." (that collapses the paragraph to a single unstyled run — assign run.text instead), or read the SVG/EMF most template art uses (add_picture raises UnidentifiedImageError).
• Legacy .ppt must be converted first: python scripts/office/soffice.py --headless --convert-to pptx file.ppt. .potx templates unpack and pack identically — keep the .potx extension on the output.
• To reuse a template icon or image, duplicate a slide or layout that already contains it.

When filling in a template:

• If you script an XML transform, parse with defusedxml.minidom — round-tripping OOXML through xml.etree.ElementTree rewrites namespace prefixes and corrupts the deck.
• Template slots ≠ source items. If the template shows 4 team members and you have 3, delete the 4th member's entire group (image + text boxes), not just its text — then check for orphaned visuals in QA.
• One <a:p> per list item — never concatenate items into a single paragraph. Copy the sibling <a:pPr> to preserve spacing, and put b="1" on the <a:rPr> of titles, section headers, and inline labels (Status:, Owner:).
• Let bullets inherit from the layout; only add <a:buChar>, <a:buAutoNum> (numbered), or <a:buNone> to override — never a literal • in the text.
• Text with leading or trailing spaces needs xml:space="preserve" on its <a:t>.

Design Ideas

Don't create boring slides. Plain bullets on a white background won't impress anyone. Consider ideas from this list for each slide.

Before Starting

• Pick a bold, content-informed color palette: The palette should feel designed for THIS topic. If swapping your colors into a completely different presentation would still "work," you haven't made specific enough choices.
• Dominance over equality: One color should dominate (60-70% visual weight), with 1-2 supporting tones and one sharp accent. Never give all colors equal weight.
• Dark/light contrast: Dark backgrounds for title + conclusion slides, light for content ("sandwich" structure). Or commit to dark throughout for a premium feel.
• Commit to a visual motif: Pick ONE distinctive element and repeat it — rounded image frames, icons in colored circles. Carry it across every slide. Do not use a color bar or accent stripe as your motif (see Avoid list).

Color Palettes

Choose colors that match your topic — don't default to generic blue. Use these palettes as inspiration:

For Each Slide

Every slide needs a visual element — image, chart, icon, or shape. Text-only slides are forgettable.

Layout options:

• Two-column (text left, illustration on right)
• Icon + text rows (icon in colored circle, bold header, description below)
• 2x2 or 2x3 grid (image on one side, grid of content blocks on other)
• Half-bleed image (full left or right side) with content overlay

Data display:

• Large stat callouts (big numbers 60-72pt with small labels below)
• Comparison columns (before/after, pros/cons, side-by-side options)
• Timeline or process flow (numbered steps, arrows)

Visual polish:

• Icons in small colored circles next to section headers
• Italic accent text for key stats or taglines

Typography

Font names you write into the .pptx are rendered by the user's PowerPoint, not by this environment. Your visual QA renders via LibreOffice, which substitutes fonts it doesn't have — and for some fonts the substitute has different widths, so your QA preview can show text overflow (or fit) that the real deck won't have. To keep your QA trustworthy:

• Safe fonts (render true-to-width in QA and ship with Office): Arial, Calibri, Cambria, Times New Roman, Courier New, Bookman Old Style, Century Schoolbook. Use these for body text and anything where fit matters.
• Headers with personality at zero QA risk: pair a safe-list serif header (Cambria, Bookman Old Style, Century Schoolbook) with a safe-list sans body (Calibri or Arial).
• If the user asks for a font outside the safe list (e.g. Georgia or Trebuchet MS): use it where the user asked, but size those containers with extra slack (~10%) and don't trust QA text-fit on those elements.
• QA-unreliable fonts (substitute has different widths — overflow checks can be wrong): Georgia, Trebuchet MS, Impact, Arial Black, Garamond, Consolas, Palatino Linotype. Calibri Light substitution varies by environment; treat as QA-unreliable.
• Never default to Aptos — Office's post-2023 default has no metric-compatible substitute here and is missing from older Office installs, so it's unreliable on both ends.

Spacing

• 0.5" minimum margins
• 0.3-0.5" between content blocks
• Leave breathing room—don't fill every inch

Avoid (Common Mistakes)

• Don't repeat the same layout — vary columns, cards, and callouts across slides
• Don't center body text — left-align paragraphs and lists; center only titles
• Don't skimp on size contrast — titles need 36pt+ to stand out from 14-16pt body
• Don't default to blue — pick colors that reflect the specific topic
• Don't mix spacing randomly — choose 0.3" or 0.5" gaps and use consistently
• Don't style one slide and leave the rest plain — commit fully or keep it simple throughout
• Don't create text-only slides — add images, icons, charts, or visual elements; avoid plain title + bullets
• Don't forget text box padding — when aligning lines or shapes with text edges, set margin: 0 on the text box or offset the shape to account for padding
• Don't use low-contrast elements — icons AND text need strong contrast against the background
• NEVER use accent lines under titles — these are a hallmark of AI-generated slides; use whitespace or background color instead
• NEVER add decorative color bars or accent stripes — this includes: header/footer bars spanning the slide width, vertical sidebar stripes down one edge of the slide, thin accent stripes along one edge of a card or content block, and "single-side borders" on rectangles. These read as AI-generated filler. If you want to set a card apart, use a subtle background tint, a drop shadow, or an icon — not an edge stripe.
• Don't default to cream/beige backgrounds — when no background is specified, use white (FFFFFF) or the user's brand palette; avoid warm-neutral defaults like F5F5DC, FAF0E6, FAEBD7, FFF8E1
• Don't ship text that overflows its shape — if text doesn't fit, reduce font size, split across slides, or enlarge the container; never leave content cut off or spilling past bounds

QA (Required)

Your first render usually has a few real issues — overlaps, overflow, misalignment. Find and fix those, re-render only the slides you changed, and stop.

Content QA

markitdown output.pptx

Check for missing content, typos, wrong order.

When using templates, check for leftover placeholder text:

markitdown output.pptx | grep -iE "\bx{3,}\b|lorem|ipsum|\bTODO|\[insert|this.*(page|slide).*layout"

If grep returns results, fix them before declaring success.

File QA (required)

python scripts/office/validate.py output.pptx                      # built from scratch
python scripts/office/validate.py output.pptx --original src.pptx  # built from a template

If the deck came from a template, always pass --original. A template may itself contain parts the XSD rejects, so a bare run can report failures you never caused — and a genuine regression can hide among them. --original baselines the schema and slide checks against the template. The structural checks — relationships, content types, charts — ignore --original and report template-inherited problems either way, so read those on their own merits.

pptxgenjs emits chart XML PowerPoint refuses to open, and every other tool accepts: python-pptx opens those decks, LibreOffice renders them, the XSD passes them. Every failure names its fix. Fix it in the generator and rebuild.

Visual QA

Convert the slides to images (see Converting to Images) and inspect every one with vision_analyze. After staring at the generating code you tend to see what you expect rather than what rendered, so look at the images fresh (a delegate_task subagent works well for this). User-visible defects to look for:

• Text overflow or text cut off at a box or slide boundary — check this first. It is the most common defect and always user-visible. (For a font the previewer renders unreliably per Typography, the preview is approximate: trust the ~10% slack you left, not its apparent fit.)
• Overlapping elements (text through shapes, lines through words, stacked elements)
• Source citations or footers colliding with content above
• Elements too close (< 0.3" gaps) or cards/sections nearly touching
• Uneven gaps (large empty area in one place, cramped in another)
• Insufficient margin from slide edges (< 0.5")
• Columns or similar elements not aligned consistently
• Low-contrast text (e.g., light gray text on cream-colored background)
• Template decoration mispositioned after text replacement — e.g., a title underline positioned for one line, but the replaced title wrapped to two
• Low-contrast icons (e.g., dark icons on dark backgrounds without a contrasting circle)
• Text boxes too narrow causing excessive wrapping
• Leftover placeholder content

Converting to Images

Convert presentations to individual slide images for visual inspection:

python scripts/office/soffice.py --headless --convert-to pdf output.pptx
rm -f slide-*.jpg
pdftoppm -jpeg -r 150 output.pdf slide
ls -1 "$PWD"/slide-*.jpg

Pass the absolute paths printed above directly to vision_analyze. The rm clears stale images from prior runs. pdftoppm zero-pads based on page count: slide-1.jpg for decks under 10 pages, slide-01.jpg for 10-99, slide-001.jpg for 100+.

After fixes, rerun all four commands above — the PDF must be regenerated from the edited .pptx before pdftoppm can reflect your changes.

Related skills

docx (Word documents), xlsx (spreadsheets), pdf (PDF work), optional pptx-author (finance-grade model-backed decks).

Source: NousResearch/hermes-agent → skills/productivity/powerpoint/SKILL.md