sporco.metric

Image quality metrics and related functions

Note that the well-known SSIM metric is not implemented here as it is available in a number of other Python packages, including:

• scikit-image

• PyMetrikz

• Video Quality Metrics

• pyssim

Some implementations are also available in unpackaged collections of Python code:

• src

• python

Functions

mae(vref, vcmp)	Compute Mean Absolute Error (MAE) between two images.
mse(vref, vcmp)	Compute Mean Squared Error (MSE) between two images.
snr(vref, vcmp)	Compute Signal to Noise Ratio (SNR) of two images.
psnr(vref, vcmp[, rng])	Compute Peak Signal to Noise Ratio (PSNR) of two images.
isnr(vref, vdeg, vrst)	Compute Improvement Signal to Noise Ratio (ISNR) for reference, degraded, and restored images.
bsnr(vblr, vnsy)	Compute Blurred Signal to Noise Ratio (BSNR) for a blurred and noisy image.
pamse(vref, vcmp[, rescale])	Compute Perceptual-fidelity Aware Mean Squared Error (PAMSE) IQA metric [61].
gmsd(vref, vcmp[, rescale, returnMap])	Compute Gradient Magnitude Similarity Deviation (GMSD) IQA metric [62].

Function Descriptions

sporco.metric.mae(vref, vcmp)

Compute Mean Absolute Error (MAE) between two images.

Parameters:

vrefarray_like

Reference image

vcmparray_like

Comparison image

Returns:

xfloat

MAE between vref and vcmp

sporco.metric.mse(vref, vcmp)

Compute Mean Squared Error (MSE) between two images.

Parameters:

vrefarray_like

Reference image

vcmparray_like

Comparison image

Returns:

xfloat

MSE between vref and vcmp

sporco.metric.snr(vref, vcmp)

Compute Signal to Noise Ratio (SNR) of two images.

Parameters:

vrefarray_like

Reference image

vcmparray_like

Comparison image

Returns:

xfloat

SNR of vcmp with respect to vref

sporco.metric.psnr(vref, vcmp, rng=None)

Compute Peak Signal to Noise Ratio (PSNR) of two images. The PSNR calculation defaults to using the less common definition in terms of the actual range (i.e. max minus min) of the reference signal instead of the maximum possible range for the data type (i.e. \(2^b-1\) for a \(b\) bit representation).

Parameters:

vrefarray_like

Reference image

vcmparray_like

Comparison image

rngNone or int, optional (default None)

Signal range, either the value to use (e.g. 255 for 8 bit samples) or None, in which case the actual range of the reference signal is used

Returns:

xfloat

PSNR of vcmp with respect to vref

sporco.metric.isnr(vref, vdeg, vrst)

Compute Improvement Signal to Noise Ratio (ISNR) for reference, degraded, and restored images.

Parameters:

vrefarray_like

Reference image

vdegarray_like

Degraded image

vrstarray_like

Restored image

Returns:

xfloat

ISNR of vrst with respect to vref and vdeg

sporco.metric.bsnr(vblr, vnsy)

Compute Blurred Signal to Noise Ratio (BSNR) for a blurred and noisy image.

Parameters:

vblrarray_like

Blurred noise free image

vnsyarray_like

Blurred image with additive noise

Returns:

xfloat

BSNR of vnsy with respect to vblr and vdeg

sporco.metric.pamse(vref, vcmp, rescale=True)

Compute Perceptual-fidelity Aware Mean Squared Error (PAMSE) IQA metric [61]. This implementation is a translation of the reference Matlab implementation provided by the authors of [61].

Parameters:

vrefarray_like

Reference image

vcmparray_like

Comparison image

rescalebool, optional (default True)

Rescale inputs so that vref has a maximum value of 255, as assumed by reference implementation

Returns:

scorefloat

PAMSE IQA metric

sporco.metric.gmsd(vref, vcmp, rescale=True, returnMap=False)

Compute Gradient Magnitude Similarity Deviation (GMSD) IQA metric [62]. This implementation is a translation of the reference Matlab implementation provided by the authors of [62].

Parameters:

vrefarray_like

Reference image

vcmparray_like

Comparison image

rescalebool, optional (default True)

Rescale inputs so that vref has a maximum value of 255, as assumed by reference implementation

returnMapbool, optional (default False)

Flag indicating whether quality map should be returned in addition to scalar score

Returns:

scorefloat

GMSD IQA metric

quality_mapndarray

Quality map