visual-design（视觉设计）

Visual Design for Presentations

Effective visual design combines diagrams, images, and consistent theming to create engaging, professional, accessible presentations. Master mermaid diagrams, stock photography, AI image generation, colorblind-safe palettes, and visual cohesion.

Evidence-based accessibility: This skill incorporates research-based best practices for accessible visual design. See references/presentation-best-practices.md for full guidelines.

Mermaid Diagrams

Mermaid provides text-based diagramming that renders beautifully in Slidev and exports well.

Flowcharts

Best for: Processes, decision trees, workflows

Basic syntax:

graph TD
    A[Start] --> B{Decision}
    B -->|Yes| C[Action 1]
    B -->|No| D[Action 2]
    C --> E[End]
    D --> E

Direction options:

• graph TD - Top to bottom
• graph LR - Left to right
• graph RL - Right to left
• graph BT - Bottom to top

Node shapes:

graph LR
    A[Rectangle]
    B(Rounded)
    C([Stadium])
    D[[Subroutine]]
    E[(Database)]
    F((Circle))
    G>Flag]
    H{Diamond}
    I{{Hexagon}}

Arrow types:

graph LR
    A-->B      %% Solid arrow
    C-.->D     %% Dotted arrow
    E==>F      %% Thick arrow
    G-.-H      %% Dotted line
    I---J      %% Solid line

Edge labels:

graph LR
    A -->|Label text| B
    B -.->|Another label| C

Sequence Diagrams

Best for: API calls, interactions, communication flows

sequenceDiagram
    participant Client
    participant Server
    participant Database

    Client->>Server: HTTP Request
    Server->>Database: Query
    Database-->>Server: Results
    Server-->>Client: HTTP Response

Message types:

• -> Solid line
• --> Dotted line
• ->> Solid arrow
• -->> Dotted arrow

Activation boxes:

sequenceDiagram
    Client->>+Server: Request
    Server->>+Database: Query
    Database-->>-Server: Data
    Server-->>-Client: Response

Notes:

sequenceDiagram
    Client->>Server: Request
    Note right of Server: Processing
    Server->>Database: Query
    Note over Client,Server: Communication

Class Diagrams

Best for: Object-oriented design, data models, architecture

classDiagram
    class User {
        +String name
        +String email
        +login()
        +logout()
    }

    class Order {
        +int orderId
        +Date date
        +calculateTotal()
    }

    User "1" --> "*" Order : places

Relationships:

• <|-- Inheritance
• *-- Composition
• o-- Aggregation
• --> Association
• -- Link
• ..|> Realization
• .. Dependency

Visibility:

• + Public
• - Private
• # Protected
• ~ Package

State Diagrams

Best for: State machines, lifecycle, status changes

stateDiagram-v2
    [*] --> Draft
    Draft --> Review
    Review --> Approved
    Review --> Rejected
    Rejected --> Draft
    Approved --> Published
    Published --> [*]

With descriptions:

stateDiagram-v2
    [*] --> Idle
    Idle --> Processing : Start
    Processing --> Complete : Success
    Processing --> Error : Failure
    Error --> Idle : Retry
    Complete --> [*]

ER Diagrams

Best for: Database schemas, data relationships

erDiagram
    CUSTOMER ||--o{ ORDER : places
    ORDER ||--|{ LINE-ITEM : contains
    PRODUCT ||--o{ LINE-ITEM : includes

    CUSTOMER {
        string name
        string email
        int customerId
    }

    ORDER {
        int orderId
        date orderDate
        float total
    }

Relationship types:

• ||--|| One to one
• ||--o{ One to many
• }o--o{ Many to many
• ||--o| Zero or one

Gantt Charts

Best for: Timelines, project schedules, roadmaps

gantt
    title Project Timeline
    dateFormat YYYY-MM-DD

    section Phase 1
    Task 1           :a1, 2024-01-01, 30d
    Task 2           :after a1, 20d

    section Phase 2
    Task 3           :2024-02-01, 25d
    Task 4           :2024-02-15, 20d

Theming Diagrams

Apply consistent colors:

%%{init: {'theme':'base', 'themeVariables': {
  'primaryColor':'#3b82f6',
  'primaryTextColor':'#fff',
  'primaryBorderColor':'#2563eb',
  'lineColor':'#6b7280',
  'secondaryColor':'#8b5cf6',
  'tertiaryColor':'#f59e0b'
}}}%%
graph TD
    A[Start] --> B[Process]
    B --> C[End]

Theme presets:

• default - Standard colors
• dark - Dark mode
• forest - Green tones
• neutral - Grayscale
• base - Customizable (use themeVariables)

Diagram Selection Guide

Process or workflow? → Flowchart

• Shows steps and decisions
• Linear or branching paths
• Start and end points clear

System interaction? → Sequence Diagram

• Shows communication between components
• Time-ordered messages
• Request/response patterns

Data structure? → Class or ER Diagram

• Shows entities and relationships
• Object-oriented design
• Database schema

State changes? → State Diagram

• Shows status transitions
• Lifecycle representation
• Finite states

Timeline or schedule? → Gantt Chart

• Shows tasks over time
• Dependencies and milestones
• Project planning

Complex architecture? → Component + Flowchart

• Multiple diagram types
• Different abstraction levels
• Layered view

Stock Photography

Image Selection Criteria

Relevance:

• Directly related to slide content
• Reinforces message
• Doesn't distract

Quality:

• Minimum 1920x1080 resolution
• Sharp, well-lit
• Professional composition

Tone:

• Matches presentation style
• Appropriate for audience
• Consistent emotional impact

Diversity:

• Inclusive representation
• Varied perspectives
• Authentic, not staged

Unsplash Search Strategies

Concept-based searches:

• "team collaboration"
• "data visualization"
• "technology innovation"
• "business meeting"
• "cloud computing abstract"

Color-specific searches:

• "blue technology"
• "minimal white background"
• "dark professional"

Orientation searches:

• Add "landscape" for 16:9 slides
• Add "portrait" for split layouts

Quality indicators:

• High view count
• Professional photographer
• Editorial collection

Pexels Alternative

Similar to Unsplash, good backup source:

• Free for commercial use
• No attribution required (but appreciated)
• Good for videos too

Attribution

Include in presenter notes or final slide:

<!--
Image credits:
- Photo by [Photographer Name] on Unsplash
- https://unsplash.com/photos/[photo-id]
-->

Image Optimization

Before using:

• Resize to 1920x1080 maximum
• Compress to reduce file size
• Save in appropriate format (JPG for photos, PNG for graphics)

Tools:

• ImageMagick: convert input.jpg -resize 1920x1080 output.jpg
• Online: TinyPNG, Squoosh

AI Image Generation

DALL-E 3 Prompting

Structure:

[Subject] + [Style] + [Composition] + [Colors] + [Details] + [Quality]

Examples:

Technical presentation:

Isometric illustration of cloud infrastructure, interconnected servers
and databases, modern tech style, blue and purple gradient, clean
minimal design, high detail, professional quality

Business presentation:

Professional photograph of diverse business team in modern office,
collaborating around laptop, natural lighting, corporate environment,
blue and gray tones, shallow depth of field, high resolution

Data visualization:

Abstract data visualization, flowing connections and nodes,
information network concept, gradient from blue to cyan,
dark background, glowing elements, futuristic style, 16:9 ratio

Best practices:

• Be specific about style (photo, illustration, 3D render)
• Specify aspect ratio (16:9 for slides)
• Include lighting details for realism
• Mention color palette for consistency
• Add quality descriptors (high detail, professional)

Midjourney Prompting

Structure:

/imagine [description] --ar 16:9 --v 6 --style [style]

Examples:

Concept illustration:

/imagine neural network visualization, interconnected nodes and
pathways, abstract tech concept, electric blue and cyan,
dark background, volumetric lighting --ar 16:9 --v 6 --style raw

Architectural diagram:

/imagine microservices architecture diagram, isometric view,
containerized applications, kubernetes cluster, technical illustration,
blue white color scheme, clean lines --ar 16:9 --v 6

Parameters:

• --ar 16:9 Aspect ratio for slides
• --v 6 Version 6 (latest)
• --style raw Less artistic, more literal
• --q 2 Quality (1-2, higher = better)
• --s 50 Stylization (0-1000, lower = literal)

Stable Diffusion Prompting

Positive prompt:

professional business chart visualization, clean modern design,
blue gradient background, data analytics concept, high quality,
detailed, 4k resolution, trending on artstation

Negative prompt:

blurry, low quality, text, watermark, signature, distorted,
ugly, bad anatomy, poorly drawn

Settings:

• Steps: 30-50
• CFG Scale: 7-12
• Size: 1024x576 (16:9) or 1920x1080

AI Image Best Practices

Do:

• Generate multiple variations
• Iterate on prompts
• Specify technical requirements
• Match presentation theme
• Use consistent style across slides

Don't:

• Use first result without review
• Mix incompatible styles
• Include text in AI images (often garbled)
• Over-complicate prompts
• Ignore licensing terms

Visual Theme Development

Color Palettes

Corporate/Professional:

Primary: #1e40af (Deep Blue)
Secondary: #6b7280 (Gray)
Accent: #3b82f6 (Bright Blue)
Background: #ffffff (White)
Text: #1f2937 (Dark Gray)

Tech/Modern:

Primary: #3b82f6 (Blue)
Secondary: #8b5cf6 (Purple)
Accent: #06b6d4 (Cyan)
Background: #0f172a (Dark Navy)
Text: #f8fafc (Light)

Academic/Formal:

Primary: #1e3a8a (Navy)
Secondary: #991b1b (Maroon)
Accent: #92400e (Brown)
Background: #fef3c7 (Cream)
Text: #1c1917 (Black)

Creative/Energetic:

Primary: #dc2626 (Red)
Secondary: #f59e0b (Amber)
Accent: #8b5cf6 (Purple)
Background: #ffffff (White)
Text: #18181b (Black)

Color Theory

Complementary: Opposite on color wheel

• High contrast
• Energetic feel
• Use sparingly

Analogous: Adjacent on color wheel

• Harmonious
• Pleasing to eye
• Professional look

Monochromatic: Variations of single hue

• Cohesive
• Sophisticated
• Easy to execute

Triadic: Three equally spaced colors

• Vibrant
• Balanced
• Needs careful use

Applying Theme Consistency

Diagrams: Use theme colors in all mermaid diagrams Images: Apply filters or overlays to match palette Backgrounds: Stick to theme backgrounds throughout Text: Consistent heading and body colors Icons: Single style (outline vs filled), matching colors

Icon Systems

Styles:

• Outline (modern, clean)
• Filled (bold, impactful)
• Flat (minimalist)
• 3D (depth, realistic)

Sources:

• Heroicons (outline/filled, free)
• Feather Icons (minimalist, free)
• Font Awesome (comprehensive, free tier)
• Material Icons (Google, free)

Consistency rules:

• Single icon style per presentation
• Consistent size (e.g., all 24px)
• Theme-matched colors
• Same stroke weight

Visual Composition

Rule of Thirds

Divide slide into 3x3 grid:

• Place important elements at intersections
• Align content along grid lines
• Creates balanced, professional look

Visual Weight

Distribute elements evenly:

• Heavy elements (images, dark colors) balance with light elements
• Symmetrical or asymmetrical balance
• Avoid one heavy corner

Focal Point

Guide viewer's eye:

• Size: Larger elements draw attention
• Color: Bright or contrasting colors stand out
• Position: Center or rule-of-thirds points
• Isolation: White space around element

Contrast

Create visual hierarchy:

• Light vs dark
• Large vs small
• Bold vs thin
• Color vs grayscale

Image + Text Integration

Text Overlays on Images

Ensure readability:

---
background: './image.jpg'
class: text-center
---

<div class="backdrop-blur-sm bg-black/50 p-8">
  <h1 class="text-white text-6xl font-bold">
    Readable Title
  </h1>
</div>

Techniques:

• Dark overlay (30-70% opacity)
• Blur background behind text
• Position text in clear area
• Add drop shadow to text

Split Layouts

Image + text side-by-side:

---
layout: image-right
image: './diagram.png'
---

# Content Here

- Point 1
- Point 2
- Point 3

Balance:

• Equal visual weight on each side
• Complementary content
• Clear relationship between image and text

Visual Hierarchy

Size Hierarchy

Title (H1): 44-60pt
Subtitle (H2): 32-40pt
Section (H3): 24-32pt
Body: 18-24pt
Caption: 14-18pt

Color Hierarchy

Primary: Headlines, key data
Secondary: Subheadings, supporting text
Tertiary: Captions, notes
Neutral: Body text, backgrounds

Weight Hierarchy

Bold: Titles, emphasis, CTAs
Regular: Body text, most content
Light: Captions, metadata, fine print

Best Practices (Evidence-Based)

Diagrams

✅ Do:

• Choose diagram type matching content (flowchart for process, sequence for interaction)
• Apply theme colors consistently via mermaid init directive
• Keep diagrams simple (max 7-9 nodes - cognitive load research)
• Label clearly with readable font sizes (match slide minimum 18pt)
• Use directional flow (typically left-to-right or top-to-bottom)
• Progressive disclosure for complex diagrams (build across multiple slides)
• Test colorblind-safe (use patterns/shapes + color, not color alone)

❌ Don't:

• Overcomplicate with too many connections (cognitive overload)
• Use too many colors (stick to theme palette: 2 main + 1-2 accents)
• Make text too small (minimum 18pt equivalent in diagrams)
• Create bidirectional spaghetti (unclear flow)
• Ignore alignment (clean grid-based layout)
• Rely on color alone (add labels, patterns, icons for colorblind accessibility)

Images

✅ Do:

• Use high-resolution (1920x1080+)
• Match presentation tone
• Ensure diversity and inclusion
• Provide attribution
• Optimize file size

❌ Don't:

• Use pixelated or blurry images
• Choose cliché stock photos
• Ignore licensing
• Use inconsistent styles
• Overload with images

Color (Accessibility Required)

✅ Do:

• Define palette upfront (2 main colors + 1-2 accents = 3-4 total)
• Ensure contrast ratios (from research):

- Normal text (<24pt): Minimum 4.5:1 - Large text (≥24pt): Minimum 3:1 - Test with tools: WebAIM Contrast Checker, Colorblind Web Page Filter

• Use colorblind-safe palettes:

- Use ColorBrewer (colorbrewer2.org) for verified palettes - Common safe combinations: Blue + Orange, Purple + Green, Blue + Red - AVOID: Red + Green (most common colorblindness)

• Don't rely on color alone:

- Add patterns in charts (stripes, dots, hatching) - Use labels and icons alongside colors - Differentiate with size/shape + color

• Use consistently throughout (same meaning = same color)
• Test on different displays (projector, laptop, mobile)

❌ Don't:

• Use random colors (establish theme palette first)
• Rely on color alone (excludes 8% of males with colorblindness)
• Create low contrast (<4.5:1 fails accessibility standards)
• Mix too many palettes (max 3-4 colors total)
• Ignore accessibility (legal requirement in many contexts)
• Use red+green together without additional differentiation

Theme

✅ Do:

• Establish visual identity
• Apply consistently
• Create templates
• Document color codes
• Test in different contexts

❌ Don't:

• Change style mid-presentation
• Mix incompatible aesthetics
• Ignore brand guidelines
• Over-decorate
• Sacrifice readability for style

Quick Reference

Mermaid Diagram Types

Flowchart: graph TD
Sequence: sequenceDiagram
Class: classDiagram
State: stateDiagram-v2
ER: erDiagram
Gantt: gantt

Color Palette Templates (Colorblind-Safe)

Blue + Orange (Recommended - Universally accessible):

primary: "#3b82f6"      # Blue (trust, tech)
secondary: "#f97316"    # Orange (energy, action)
neutral: "#6b7280"      # Gray (backgrounds)
text: "#1f2937"         # Dark gray (body text)
background: "#ffffff"   # White (slide background)

# Contrast ratios:
# Blue on white: 8.6:1 ✓
# Orange on white: 3.4:1 (use for headings ≥24pt) ✓
# Text on white: 16.1:1 ✓

Purple + Teal (Professional, modern):

primary: "#8b5cf6"      # Purple (creative, innovative)
secondary: "#14b8a6"    # Teal (calm, balanced)
neutral: "#64748b"      # Slate gray
text: "#0f172a"         # Near black
background: "#ffffff"   # White

Dark Mode (High contrast):

primary: "#60a5fa"      # Light blue (readable on dark)
secondary: "#fbbf24"    # Amber (attention)
neutral: "#475569"      # Slate (dividers)
text: "#f1f5f9"         # Light gray (body text)
background: "#0f172a"   # Very dark blue

# Note: Dark mode requires ≥7:1 contrast for text

Verification checklist:

• Contrast ratios verified (4.5:1+ for normal, 3:1+ for large text)
• Tested with colorblind simulator
• Colors have distinct meaning (not red/green for pass/fail)
• Patterns/icons supplement color in charts
• Palette documented for consistency

Image Checklist

• High resolution (1920x1080+)
• Relevant to content
• Matches presentation tone
• Properly attributed
• Optimized file size
• Accessible (alt text in notes)

For advanced mermaid syntax and visual design principles, consult the Mermaid documentation (https://mermaid.js.org/) and design resources like Refactoring UI.