ComfyUI Smart Aspect Ratio

A ComfyUI custom node that converts a megapixel target and aspect ratio into pixel dimensions (width × height). The ratio can be fixed, randomized, or detected automatically from a connected prompt.

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Features

• 23 aspect ratios from 1:1 to 32:9 (portrait, square, landscape)
• Prompt-based detection — connect your text prompt and the node picks the right ratio automatically
• Explicit ratio override — writing 16:9 anywhere in the prompt forces that exact ratio
• Keyword matching — terms like cinematic, widescreen, portrait, or anamorphic map to weighted ratio pools
• Randomization — seed-controlled random ratio when nothing is detected
• Editable keyword rules — click Edit Keywords on the node to add, remove, or modify rules live

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Installation

Via ComfyUI Manager: search for Smart Resolution.

Manual:

cd ComfyUI/custom_nodes
git clone https://github.com/YOUR_GITHUB_USERNAME/comfyui-ResolutionAndAspectRatio

Restart ComfyUI. The node appears under the Resolution category.

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Inputs

Input	Type	Description
megapixels	Dropdown	Target image size, 0.1–2.5 MP
aspect_ratio	Dropdown	Fallback ratio when detection is off or finds nothing
divisible_by	Dropdown	Round dimensions to this multiple (8 / 16 / 32 / 64)
keyword_mode	Dropdown	Controls which prompt keywords trigger detection
randomize	Boolean	Pick a random ratio when no keyword/prompt match fires
seed	INT	Controls which ratio is picked when randomizing
prompt	STRING (optional)	Text to scan — connect to the same node as your CLIP encoder

Outputs

Output	Description
width	Image width in pixels
height	Image height in pixels
ratio	Selected ratio with detection source, e.g. 16:9 (cinematic)

divisible_by 64 works for most models (SD 1.5, SDXL). Use 8 or 16 for custom VAEs.

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Ratio Detection

Detection runs in this priority order:

1. Explicit ratio in the prompt — 16:9 anywhere forces that exact ratio
2. Keyword match — picks from a weighted pool based on matched term
3. Fallback — fixed aspect_ratio dropdown, or random if Randomize is on

The ratio output string shows what triggered the selection: 21:9 (from prompt), 16:9 (cinematic), etc. Connect it to a Show Text node to monitor it.

Keyword Mode

Mode	What triggers
Off	Nothing — uses fixed or random ratio
AR only	Only explicit ratios written in the prompt
Limited keywords (default)	Explicit ratios + unambiguous AR terms
All keywords	Explicit ratios + all rules including content words

Limited keywords only matches terms that clearly describe a format (widescreen, anamorphic, ultrawide). All keywords also catches content words like cinematic, portrait, poster, or phone.

Default Keyword Rules

Words	Ratio pool	Mode
anamorphic	21:9	Limited+
imax	4:3	Limited+
ultrawide	21:9 32:9	Limited+
widescreen	16:9 19:9 21:9	Limited+
panorama, panoramic	16:9 19:9 21:9 32:9	Limited+
square, avatar, thumbnail	1:1	All
mobile, phone, smartphone	9:16 9:19 9:21	All
poster	2:3 3:4 4:5	All
cinematic	16:9 21:9 32:9	All
banner	16:9 21:9 32:9	All
wallpaper	16:9 21:9 32:9	All
landscape, horizontal, wide angle, wide shot	All landscape ratios	All
portrait, vertical, tall	All portrait ratios	All

When a keyword maps to multiple ratios, one is picked by weighted random using the seed. Change the seed for a different pick within the same pool.

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Editing Keywords

Click Edit Keywords on the node to open the live editor. Each rule has:

• Words — comma-separated trigger words/phrases (case-insensitive, phrase-aware)
• Ratios — comma-separated ratio pool, or $LANDSCAPE / $PORTRAIT for the full sets
• Weights — optional; controls probability of each ratio (leave blank for equal chance)
• Category — limited = active in Limited + All modes; all = active in All mode only

Changes are saved to keywords.json in the node folder and take effect immediately.

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Supported Aspect Ratios

Portrait: 2:3 3:4 3:5 4:5 5:7 5:8 7:9 9:16 9:19 9:21 9:32

Square: 1:1

Landscape: 3:2 4:3 5:3 5:4 7:5 8:5 9:7 16:9 19:9 21:9 32:9

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License

MIT