To Canvas JSON Skill

This skill enables skills-compatible agents to create and edit valid JSON Canvas files (.canvas) used in Obsidian and other applications.

Overview

JSON Canvas is an open file format for infinite canvas data. Canvas files use the .canvas extension and contain valid JSON following the JSON Canvas Spec 1.0.

File Structure

A canvas file contains two top-level arrays:

{
  "nodes": [],
  "edges": []
}

• nodes (optional): Array of node objects
• edges (optional): Array of edge objects connecting nodes

Nodes

Nodes are objects placed on the canvas. There are four node types:

• text - Text content with Markdown
• file - Reference to files/attachments
• link - External URL
• group - Visual container for other nodes

Z-Index Ordering

Nodes are ordered by z-index in the array:

• First node = bottom layer (displayed below others)
• Last node = top layer (displayed above others)

Generic Node Attributes

All nodes share these attributes:

Text Nodes

Text nodes contain Markdown content.

{
  "id": "6f0ad84f44ce9c17",
  "type": "text",
  "x": 0,
  "y": 0,
  "width": 400,
  "height": 200,
  "text": "# Hello World\n\nThis is **Markdown** content."
}

File Nodes

File nodes reference files or attachments (images, videos, PDFs, notes, etc.).

{
  "id": "a1b2c3d4e5f67890",
  "type": "file",
  "x": 500,
  "y": 0,
  "width": 400,
  "height": 300,
  "file": "Attachments/diagram.png"
}

{
  "id": "b2c3d4e5f6789012",
  "type": "file",
  "x": 500,
  "y": 400,
  "width": 400,
  "height": 300,
  "file": "Notes/Project Overview.md",
  "subpath": "#Implementation"
}

Link Nodes

Link nodes display external URLs.

{
  "id": "c3d4e5f678901234",
  "type": "link",
  "x": 1000,
  "y": 0,
  "width": 400,
  "height": 200,
  "url": "https://obsidian.md"
}

Group Nodes

Group nodes are visual containers for organizing other nodes.

{
  "id": "d4e5f6789012345a",
  "type": "group",
  "x": -50,
  "y": -50,
  "width": 1000,
  "height": 600,
  "label": "Project Overview",
  "color": "4"
}

{
  "id": "e5f67890123456ab",
  "type": "group",
  "x": 0,
  "y": 700,
  "width": 800,
  "height": 500,
  "label": "Resources",
  "background": "Attachments/background.png",
  "backgroundStyle": "cover"
}

Background Styles

Edges

Edges are lines connecting nodes.

{
  "id": "f67890123456789a",
  "fromNode": "6f0ad84f44ce9c17",
  "toNode": "a1b2c3d4e5f67890"
}

{
  "id": "0123456789abcdef",
  "fromNode": "6f0ad84f44ce9c17",
  "fromSide": "right",
  "fromEnd": "none",
  "toNode": "b2c3d4e5f6789012",
  "toSide": "left",
  "toEnd": "arrow",
  "color": "1",
  "label": "leads to"
}

Side Values

End Shapes

Colors

The canvasColor type can be specified in two ways:

Hex Colors

{
  "color": "#FF0000"
}

Preset Colors

{
  "color": "1"
}

Note: Specific color values for presets are intentionally undefined, allowing applications to use their own brand colors.

Complete Examples

Simple Canvas with Text and Connections

{
  "nodes": [
    {
      "id": "8a9b0c1d2e3f4a5b",
      "type": "text",
      "x": 0,
      "y": 0,
      "width": 300,
      "height": 150,
      "text": "# Main Idea\n\nThis is the central concept."
    },
    {
      "id": "1a2b3c4d5e6f7a8b",
      "type": "text",
      "x": 400,
      "y": -100,
      "width": 250,
      "height": 100,
      "text": "## Supporting Point A\n\nDetails here."
    },
    {
      "id": "2b3c4d5e6f7a8b9c",
      "type": "text",
      "x": 400,
      "y": 100,
      "width": 250,
      "height": 100,
      "text": "## Supporting Point B\n\nMore details."
    }
  ],
  "edges": [
    {
      "id": "3c4d5e6f7a8b9c0d",
      "fromNode": "8a9b0c1d2e3f4a5b",
      "fromSide": "right",
      "toNode": "1a2b3c4d5e6f7a8b",
      "toSide": "left"
    },
    {
      "id": "4d5e6f7a8b9c0d1e",
      "fromNode": "8a9b0c1d2e3f4a5b",
      "fromSide": "right",
      "toNode": "2b3c4d5e6f7a8b9c",
      "toSide": "left"
    }
  ]
}

Project Board with Groups

{
  "nodes": [
    {
      "id": "5e6f7a8b9c0d1e2f",
      "type": "group",
      "x": 0,
      "y": 0,
      "width": 300,
      "height": 500,
      "label": "To Do",
      "color": "1"
    },
    {
      "id": "6f7a8b9c0d1e2f3a",
      "type": "group",
      "x": 350,
      "y": 0,
      "width": 300,
      "height": 500,
      "label": "In Progress",
      "color": "3"
    },
    {
      "id": "7a8b9c0d1e2f3a4b",
      "type": "group",
      "x": 700,
      "y": 0,
      "width": 300,
      "height": 500,
      "label": "Done",
      "color": "4"
    },
    {
      "id": "8b9c0d1e2f3a4b5c",
      "type": "text",
      "x": 20,
      "y": 50,
      "width": 260,
      "height": 80,
      "text": "## Task 1\n\nImplement feature X"
    },
    {
      "id": "9c0d1e2f3a4b5c6d",
      "type": "text",
      "x": 370,
      "y": 50,
      "width": 260,
      "height": 80,
      "text": "## Task 2\n\nReview PR #123",
      "color": "2"
    },
    {
      "id": "0d1e2f3a4b5c6d7e",
      "type": "text",
      "x": 720,
      "y": 50,
      "width": 260,
      "height": 80,
      "text": "## Task 3\n\n~~Setup CI/CD~~"
    }
  ],
  "edges": []
}

Research Canvas with Files and Links

{
  "nodes": [
    {
      "id": "1e2f3a4b5c6d7e8f",
      "type": "text",
      "x": 300,
      "y": 200,
      "width": 400,
      "height": 200,
      "text": "# Research Topic\n\n## Key Questions\n\n- How does X affect Y?\n- What are the implications?",
      "color": "5"
    },
    {
      "id": "2f3a4b5c6d7e8f9a",
      "type": "file",
      "x": 0,
      "y": 0,
      "width": 250,
      "height": 150,
      "file": "Literature/Paper A.pdf"
    },
    {
      "id": "3a4b5c6d7e8f9a0b",
      "type": "file",
      "x": 0,
      "y": 200,
      "width": 250,
      "height": 150,
      "file": "Notes/Meeting Notes.md",
      "subpath": "#Key Insights"
    },
    {
      "id": "4b5c6d7e8f9a0b1c",
      "type": "link",
      "x": 0,
      "y": 400,
      "width": 250,
      "height": 100,
      "url": "https://example.com/research"
    },
    {
      "id": "5c6d7e8f9a0b1c2d",
      "type": "file",
      "x": 750,
      "y": 150,
      "width": 300,
      "height": 250,
      "file": "Attachments/diagram.png"
    }
  ],
  "edges": [
    {
      "id": "6d7e8f9a0b1c2d3e",
      "fromNode": "2f3a4b5c6d7e8f9a",
      "fromSide": "right",
      "toNode": "1e2f3a4b5c6d7e8f",
      "toSide": "left",
      "label": "supports"
    },
    {
      "id": "7e8f9a0b1c2d3e4f",
      "fromNode": "3a4b5c6d7e8f9a0b",
      "fromSide": "right",
      "toNode": "1e2f3a4b5c6d7e8f",
      "toSide": "left",
      "label": "informs"
    },
    {
      "id": "8f9a0b1c2d3e4f5a",
      "fromNode": "4b5c6d7e8f9a0b1c",
      "fromSide": "right",
      "toNode": "1e2f3a4b5c6d7e8f",
      "toSide": "left",
      "toEnd": "arrow",
      "color": "6"
    },
    {
      "id": "9a0b1c2d3e4f5a6b",
      "fromNode": "1e2f3a4b5c6d7e8f",
      "fromSide": "right",
      "toNode": "5c6d7e8f9a0b1c2d",
      "toSide": "left",
      "label": "visualized by"
    }
  ]
}

Flowchart

{
  "nodes": [
    {
      "id": "a0b1c2d3e4f5a6b7",
      "type": "text",
      "x": 200,
      "y": 0,
      "width": 150,
      "height": 60,
      "text": "**Start**",
      "color": "4"
    },
    {
      "id": "b1c2d3e4f5a6b7c8",
      "type": "text",
      "x": 200,
      "y": 100,
      "width": 150,
      "height": 60,
      "text": "Step 1:\nGather data"
    },
    {
      "id": "c2d3e4f5a6b7c8d9",
      "type": "text",
      "x": 200,
      "y": 200,
      "width": 150,
      "height": 80,
      "text": "**Decision**\n\nIs data valid?",
      "color": "3"
    },
    {
      "id": "d3e4f5a6b7c8d9e0",
      "type": "text",
      "x": 400,
      "y": 200,
      "width": 150,
      "height": 60,
      "text": "Process data"
    },
    {
      "id": "e4f5a6b7c8d9e0f1",
      "type": "text",
      "x": 0,
      "y": 200,
      "width": 150,
      "height": 60,
      "text": "Request new data",
      "color": "1"
    },
    {
      "id": "f5a6b7c8d9e0f1a2",
      "type": "text",
      "x": 400,
      "y": 320,
      "width": 150,
      "height": 60,
      "text": "**End**",
      "color": "4"
    }
  ],
  "edges": [
    {
      "id": "a6b7c8d9e0f1a2b3",
      "fromNode": "a0b1c2d3e4f5a6b7",
      "fromSide": "bottom",
      "toNode": "b1c2d3e4f5a6b7c8",
      "toSide": "top"
    },
    {
      "id": "b7c8d9e0f1a2b3c4",
      "fromNode": "b1c2d3e4f5a6b7c8",
      "fromSide": "bottom",
      "toNode": "c2d3e4f5a6b7c8d9",
      "toSide": "top"
    },
    {
      "id": "c8d9e0f1a2b3c4d5",
      "fromNode": "c2d3e4f5a6b7c8d9",
      "fromSide": "right",
      "toNode": "d3e4f5a6b7c8d9e0",
      "toSide": "left",
      "label": "Yes",
      "color": "4"
    },
    {
      "id": "d9e0f1a2b3c4d5e6",
      "fromNode": "c2d3e4f5a6b7c8d9",
      "fromSide": "left",
      "toNode": "e4f5a6b7c8d9e0f1",
      "toSide": "right",
      "label": "No",
      "color": "1"
    },
    {
      "id": "e0f1a2b3c4d5e6f7",
      "fromNode": "e4f5a6b7c8d9e0f1",
      "fromSide": "top",
      "fromEnd": "none",
      "toNode": "b1c2d3e4f5a6b7c8",
      "toSide": "left",
      "toEnd": "arrow"
    },
    {
      "id": "f1a2b3c4d5e6f7a8",
      "fromNode": "d3e4f5a6b7c8d9e0",
      "fromSide": "bottom",
      "toNode": "f5a6b7c8d9e0f1a2",
      "toSide": "top"
    }
  ]
}

ID Generation

Node and edge IDs must be unique strings. Obsidian generates 16-character hexadecimal IDs:

"id": "6f0ad84f44ce9c17"
"id": "a3b2c1d0e9f8g7h6"
"id": "1234567890abcdef"

This format is a 16-character lowercase hex string (64-bit random value).

Dimension Calculation Script

Use scripts/calculate_canvas_dimensions.py to automatically calculate correct dimensions:

# Calculate dimensions and write to new file
python scripts/calculate_canvas_dimensions.py input.canvas -o output.canvas

# Calculate dimensions in place
python scripts/calculate_canvas_dimensions.py input.canvas --in-place

# Options
python scripts/calculate_canvas_dimensions.py input.canvas --no-heights    # Keep text heights
python scripts/calculate_canvas_dimensions.py input.canvas --widths        # Also calc widths
python scripts/calculate_canvas_dimensions.py input.canvas --no-groups     # Keep group sizes
python scripts/calculate_canvas_dimensions.py input.canvas --no-reflow     # Don't shift groups

The script performs three passes:

1. Text heights: Calculates heights based on content (headers, code blocks, tables, lists)
2. Group bounds: Calculates group dimensions to contain all child nodes with padding
3. Reflow: Shifts groups vertically to prevent overlaps (maintains 50px gap)

Always run this script after creating or modifying a canvas to ensure proper sizing.

Layout Guidelines

Positioning

• Coordinates can be negative (canvas extends infinitely)
• x increases to the right
• y increases downward
• Position refers to top-left corner of node

Content-Based Height Calculation

IMPORTANT: Always calculate height based on actual content to ensure all text is visible.

Height Formula

height = PADDING + (line_count * LINE_HEIGHT) + HEADER_EXTRA + CODE_BLOCK_EXTRA + TABLE_EXTRA

Constants:

Calculating Line Count

1. Count explicit newlines: text.count('\n') + 1
2. Account for text wrapping: For width W, estimate wrapped lines per logical line:
   • Regular text: ~8-10 chars per 100px width
   • Code: ~7-8 chars per 100px width (monospace)
   • For width 300px: ~24-30 chars before wrap

Quick Reference

Examples

Simple text (3 lines):

"# Title\n\nTwo lines of content."
Lines: 3 (title + blank + content)
Height: 24 + (3 × 22) + 16 = 106 → round to 110

Code block:

"## Config\n\n```python\nx = 1\ny = 2\nz = 3\n```"
Lines: 7 total, 3 code lines
Height: 24 + (2 × 22) + 12 + 16 + (3 × 20) = 138 → round to 140

Table:

"| Col A | Col B |\n|-------|-------|\n| val1 | val2 |\n| val3 | val4 |"
Header: 1, Separator: skip, Data rows: 2
Height: 24 + 32 + (2 × 28) = 112 → round to 120

Width Guidelines for Readable Content

Maximum Height

For very long content, cap height at 800px and accept that users will scroll in Obsidian. Better to have scrollable content than a canvas that's hard to navigate.

height = min(calculated_height, 800)

Recommended Sizes (Static Fallback)

When content length is unknown, use these defaults:

Group Sizing Based on Children

IMPORTANT: Group dimensions must contain all child nodes with padding.

Group Height Formula

group_height = (max_child_bottom - group_y) + BOTTOM_PADDING

Where:

• max_child_bottom = max(child_y + child_height) for all children
• BOTTOM_PADDING = 40-60px

Group Positioning

1. Set group y = first_child_y - 60 (for label + top padding)
2. Set group x = min(child_x) - 50 (left padding)
3. Calculate width from rightmost child: max(child_x + child_width) - group_x + 50
4. Calculate height from bottom child: max(child_y + child_height) - group_y + 50

Example

Children positions:

• Node A: y=700, height=340 → bottom at 1040
• Node B: y=700, height=360 → bottom at 1060

Group calculation:

• group_y = 700 - 60 = 640
• group_height = 1060 - 640 + 50 = 470

Spacing

• Leave 50-60px padding inside groups (top, bottom, sides)
• Space nodes 50-100px apart for readability
• Align nodes to grid (multiples of 10 or 20) for cleaner layouts
• Leave 50-100px gap between adjacent groups

Validation Rules

1. All id values must be unique across nodes and edges
2. fromNode and toNode must reference existing node IDs
3. Required fields must be present for each node type
4. type must be one of: text, file, link, group
5. backgroundStyle must be one of: cover, ratio, repeat
6. fromSide, toSide must be one of: top, right, bottom, left
7. fromEnd, toEnd must be one of: none, arrow
8. Color presets must be "1" through "6" or valid hex color

References

• JSON Canvas Spec 1.0
• JSON Canvas GitHub