SVG Architecture Diagram

Create professional technical architecture diagrams using pure SVG, rendered to high-res PNG via Playwright.

Why SVG (not CSS positioning or AI image generation)

Approach	Lines/Arrows	Text Quality	Precision
----------	-------------	-------------	-----------
SVG (this skill)	✅ Perfect: , ,	✅ Crisp at any size	✅ Pixel-perfect
CSS absolute positioning	❌ Hacky: borders, pseudo-elements	✅ OK	❌ Hard to align
AI image generation	❌ No control	❌ Garbled text	❌ No precision

Quick Start

Step 1: Plan the diagram

Identify:

Modules — group related components (color-coded)
Hierarchy — top-to-bottom flow (user → core → subsystems → output)
Connections — data flow (solid lines), feedback (dashed lines)

Step 2: Create the HTML file

Write a single HTML file with an inline SVG. Standard canvas: 1600×1000px.

<!DOCTYPE html>
<html><head>
<meta charset="UTF-8">
<style>
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');
* { margin: 0; padding: 0; box-sizing: border-box; }
body { width: 1600px; height: 1000px; background: #fafafa; overflow: hidden; }
</style>
</head><body>
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1600 1000" width="1600" height="1000">
  <defs>
    <!-- Arrow markers — one per color -->
    <marker id="arr-indigo" markerWidth="8" markerHeight="6" refX="7" refY="3" orient="auto">
      <path d="M0,0 L8,3 L0,6 Z" fill="#6366f1"/>
    </marker>
    <!-- Shadow filter -->
    <filter id="shadow" x="-4%" y="-4%" width="108%" height="108%">
      <feDropShadow dx="0" dy="2" stdDeviation="4" flood-color="#000" flood-opacity="0.08"/>
    </filter>
  </defs>

  <!-- Diagram content here -->

</svg>
</body></html>

Step 3: Build the diagram using these SVG patterns

Filled header card (module title):

<rect x="X" y="Y" width="W" height="40" rx="10" fill="#6366f1" filter="url(#shadow)"/>
<text x="CENTER" y="Y+25" text-anchor="middle" font-size="13" font-weight="700" fill="#fff">🔄 Module Name</text>

Outlined detail card (sub-component):

<rect x="X" y="Y" width="W" height="65" rx="10" fill="#fff" stroke="#6366f1" stroke-width="2" filter="url(#shadow)"/>
<text x="X+20" y="Y+22" font-size="12" font-weight="700" fill="#6366f1">Component Title</text>
<text x="X+20" y="Y+40" font-size="11" fill="#6b7280">Description line 1</text>
<text x="X+20" y="Y+55" font-size="10" fill="#9ca3af">Metadata / specs</text>

Connection line (with arrow):

<line x1="FROM_X" y1="FROM_Y" x2="TO_X" y2="TO_Y" stroke="#6366f1" stroke-width="2" marker-end="url(#arr-indigo)"/>

Curved connection (L-shape or bend):

<path d="M startX,startY L midX,midY L endX,endY" stroke="#6366f1" stroke-width="2" fill="none" marker-end="url(#arr-indigo)"/>

Dashed feedback line:

<path d="M x1,y1 L x2,y2" stroke="#8b5cf6" stroke-width="2" fill="none" stroke-dasharray="6,4" marker-end="url(#arr-purple)"/>

Connection label:

<text x="MID_X" y="MID_Y-5" font-size="10" fill="#6366f1" font-weight="500">label text</text>

Step 4: Screenshot with Playwright

from playwright.sync_api import sync_playwright
with sync_playwright() as p:
    browser = p.chromium.launch()
    page = browser.new_page(
        viewport={"width": 1600, "height": 1000},
        device_scale_factor=4,  # 4x ultra-high res (default)
    )
    page.goto("file:///path/to/diagram.html", wait_until="networkidle")
    page.wait_for_timeout(1500)
    page.screenshot(path="diagram.png", full_page=True)
    browser.close()

Or use the bundled script: scripts/screenshot.py [output.png]

Design System

See references/design-system.md for the complete color palette, card styles, arrow markers, and text sizing rules.

Critical Rules (prevent common issues)

Text Overflow Prevention

Max characters per line at font-size 11px ≈ 7px/char:

300px container → max 37 chars
340px container → max 43 chars
440px container → max 57 chars

Long text → split into multiple elements with Y offset +15px each
Always leave 20px padding on each side of text inside cards
Test at 1x scale before generating final 4x screenshot

Connection Line Rules

Never use CSS for connections — always SVG or
One per color — define in , reference with marker-end
Straight lines when possible; use L-segments for bends
Avoid crossing lines — rearrange layout if lines would cross
Label every connection — brief verb/noun near the midpoint
⚠️ Minimum 20px gap between vertically stacked cards — Arrow markers are 8px long. If the gap between cards is less than 20px, the arrow will completely cover the line, making it look like "arrow only, no line". Use card height 34px + gap 22px = 56px per step.
Connection line length must be at least 17px — This ensures 9px visible line + 8px arrow marker. Example: card bottom at y=324, next card top at y=346, line from y1=324 to y2=343 (19px).
Never make line length < marker size (8px) — The line will be invisible.

Layout Rules

Top-to-bottom primary flow (input at top, output at bottom/right)
Left-right symmetry when possible
Group related modules vertically (e.g., memory layers stacked)
Minimum 20px gap between vertically stacked cards (see Connection Line Rules)
Color-code by function — see design system for standard palette
Include a legend (bottom-right corner) explaining colors and line types
Include a title (top center) and source attribution (bottom center)

Font Rules

Font family: font-family="Inter, 'PingFang SC', 'Microsoft YaHei', sans-serif" — set on root or first
Load Inter via Google Fonts in

SVG Architecture Diagram

概述

SVG Architecture Diagram

Why SVG (not CSS positioning or AI image generation)

Quick Start

Step 1: Plan the diagram

Step 2: Create the HTML file

Step 3: Build the diagram using these SVG patterns

Step 4: Screenshot with Playwright

Design System

Critical Rules (prevent common issues)

Text Overflow Prevention

Connection Line Rules

Layout Rules

Font Rules