Module capacity 

Ghost mode capacity estimation.

Estimates the maximum plaintext message size that can be embedded in a given JPEG cover image using Ghost mode. The estimate accounts for:

• Number of usable (non-WET) AC coefficients
• Minimum capacity ratio to ensure reliable STC embedding
• Frame overhead (length, salt, nonce, auth tag, CRC)

Functions

estimate_capacity

Estimate Ghost mode capacity (standard J-UNIWARD).

estimate_capacity_si

Estimate Ghost mode capacity with SI-UNIWARD (“Deep Cover”).

estimate_capacity_with_shadows

Estimate Ghost primary capacity accounting for shadow position overhead.

estimate_shadow_capacity

Estimate shadow layer capacity for a JPEG image.