CFA Phase
Definition
The spatial offset of the CFA mosaic pattern in an image. Pasting a region from a different image or after a non-CFA-aligned crop can introduce a phase shift that breaks the expected periodic pattern.
- Definition
- Spatial offset of the CFA mosaic pattern
- Disrupted by
- Pasting or misaligned cropping
- Detection use
- Splicing and forgery detection
- Underlying pattern
- Typically Bayer RGGB
- Related concept
- CFA inconsistency detection
Common questions
Why does a one-pixel crop offset matter for CFA phase analysis?+
The CFA pattern repeats on a fixed small grid, commonly two by two pixels, so shifting a pasted region by even a single pixel relative to that grid misaligns its phase from the surrounding image, producing a detectable seam in the demosaicing statistics.
Can CFA phase analysis be defeated?+
Yes, a sufficiently careful forger who resamples or re-renders a spliced region to match the target image's CFA grid can reduce or eliminate the phase discontinuity, which is why phase analysis is normally used alongside other tamper-detection methods, not alone.
Related terms
- Camera Noise Model
- A mathematical description of a sensor's noise as a function of signal level, combining signal-dependent shot noise and signal-independent readout noise. The...
- CFA (Colour Filter Array)
- The mosaic of colour filters placed over a sensor so that each photosite captures one colour channel. The Bayer pattern (RGGB arrangement)...
- Demosaicing
- The algorithm used to interpolate full-colour pixel values from the single-channel raw sensor data. Common methods include bilinear interpolation, gradient-based algorithms (AHD,...
- Noise Residual
- The signal remaining after a denoising filter removes the scene component from an image. For PRNU estimation, the residual approximates the sum...
- Steganography
- Concealing one file inside another in a way that hides the existence of the hidden file. LSB image manipulation, JPEG DCT coefficient...