Comfy-Org/ComfyUI · error · ValueError

Aspect ratio parts must be positive integers, got {a}:{b}.

Error message

Aspect ratio parts must be positive integers, got {a}:{b}.

What it means

Raised by _parse_aspect_ratio_string() in comfy_api_nodes/util/validation_utils.py when both parts parse as integers but one is zero or negative. The helper must return a positive float ratio, so '0:9', '-16:9', or '16:0' are rejected after successful int parsing.

Source

Thrown at comfy_api_nodes/util/validation_utils.py:244

            raise ValueError(f"Aspect ratio `{ar:.2g}` must be {op} {lo:.2g}.")
    if hi is not None:
        if (ar >= hi) if strict else (ar > hi):
            op = "<" if strict else "≤"
            raise ValueError(f"Aspect ratio `{ar:.2g}` must be {op} {hi:.2g}.")


def _parse_aspect_ratio_string(ar_str: str) -> float:
    """Parse 'X:Y' with integer parts into a positive float ratio X/Y."""
    parts = ar_str.split(":")
    if len(parts) != 2:
        raise ValueError(f"Aspect ratio must be 'X:Y' (e.g., 16:9), got '{ar_str}'.")
    try:
        a = int(parts[0].strip())
        b = int(parts[1].strip())
    except ValueError as exc:
        raise ValueError(f"Aspect ratio must contain integers separated by ':', got '{ar_str}'.") from exc
    if a <= 0 or b <= 0:
        raise ValueError(f"Aspect ratio parts must be positive integers, got {a}:{b}.")
    return a / b

View on GitHub (pinned to 1c6d8d45b3)

Solutions

1. Use positive integers on both sides, e.g. '16:9'.
2. If constructing from dimensions, validate both are > 0 before formatting the string.
3. Fix the upstream computation that produced a zero dimension (bad load, empty tensor shape).
4. Guard with a default ratio when dimensions are unknown.

Example fix

# before
w, h = 0, 9
_parse_aspect_ratio_string(f'{w}:{h}')  # ValueError: parts must be positive integers, got 0:9.

# after
assert w > 0 and h > 0, 'dimensions must be positive'
_parse_aspect_ratio_string(f'{w}:{h}')

a, b = (int(p.strip()) for p in ratio_str.split(':'))
if a <= 0 or b <= 0:
    raise ValueError(f'degenerate ratio {ratio_str!r}; both parts must be > 0')

def is_positive_int_ratio(s: str) -> bool:
    parts = s.split(':')
    if len(parts) != 2: return False
    try:
        a, b = int(parts[0].strip()), int(parts[1].strip())
        return a > 0 and b > 0
    except ValueError:
        return False

When it happens

Trigger: Passing '0:0', '16:0', '0:9', or negative components like '-1:1' through validate_aspect_ratio — usually from programmatic construction where a width or height was 0 (e.g. 'derive height from aspect' computed 0).

Common situations: Scripts building the ratio string from image dimensions where one dimension is 0 due to a failed load or a division that collapsed to zero; users experimenting with degenerate values; template substitution inserting an unset variable as 0.

Related errors

• Aspect ratio must be 'X:Y' (e.g., 16:9), got '{ar_str}'.
• Aspect ratio must contain integers separated by ':', got '{a
• Ratios must be positive, got {a}:{b}.
• Aspect ratio `{ar:.2g}` must be {op} {lo:.2g}.
• Aspect ratio `{ar:.2g}` must be {op} {hi:.2g}.

AI-assisted analysis of Comfy-Org/ComfyUI@1c6d8d45b3 (2026-08-14). Data as JSON: /api/errors/996d06950d954e8a. Report an issue: GitHub.