StainTools

Tools for stain normalization and augmentation in Python (tested on 3.5). GitHub repository here.

Latest build:

Install

pip install staintools

Note: StainTools requires the SPAMS (SPArse Modeling Software) package. Please find out about this here. This may be easily installed via conda. For example, see here.

Example usage

Please see demo.ipynb here.

Docs

Made with Sphinx and Read the Docs here.

Contents

Normalization

Abstract base classes

Normalizer abstract base classes

class staintools.normalization.normalizer_abc.FancyNormalizer(**kwargs)

Abstract class for a ‘fancy’ normalizer (inherits from Normalizer). Adds methods for stain matrix and source concentration estimation.

fetch_target_stains()

Fetch the target stain matrix and convert from OD to RGB. Must call fit first (this builds the stain matrix).

Returns:

fit(target)

Fit to a target image.

Parameters:target – Target image RGB uint8. Returns:

static get_concentrations(I, stain_matrix, lamda=0.01)

Get the concentration matrix. Suppose the input image is H x W x 3 (uint8). Define Npix = H * W. Then the concentration matrix is Npix x 2 (or we could reshape to H x W x 2). The first element of each row is the Hematoxylin concentration. The second element of each row is the Eosin concentration.

We do this by ‘solving’ OD = C*S (Matrix product) where OD is optical density (Npix x 3), C is concentration (Npix x 2) and S is stain matrix (2 x 3). See docs for spams.lasso.

We restrict the concentrations to be positive and penalise very large concentration values, so that background pixels (which can not easily be expressed in the Hematoxylin-Eosin basis) have low concentration and thus appear white.

Parameters:

• I – Image. A np array HxWx3 of type uint8.
• stain_matrix – a 2x3 stain matrix. First row is Hematoxylin stain vector, second row is Eosin stain vector.

Returns:

The Nx2 concentration matrix, where N=H*W is number of pixels.

get_stain_matrix(I, *args)

Estimate stain matrix given an image and relevant method parameters

hematoxylin(I)

Hematoxylin channel extraction.

Parameters:I – Image RGB uint8. Returns:

transform(I)

Transform an image.

Parameters:I – Image RGB uint8. Returns:

class staintools.normalization.normalizer_abc.Normaliser(**kwargs)

Abstract base class for normalizers. Defines some necessary methods to be considered a normalizer.

fit(target)

Fit the normalizer to an target image

transform(I)

Transform an image to the target stain

Reinhard method

class staintools.normalization.reinhard.ReinhardNormalizer(**kwargs)

Normalize a patch stain to the target image using the method of: E. Reinhard, M. Adhikhmin, B. Gooch, and P. Shirley, ‘Color transfer between images’, IEEE Computer Graphics and Applications, vol. 21, no. 5, pp. 34–41, Sep. 2001.

fit(target)

Fit to a target image

Parameters:target – Image RGB uint8. Returns:

get_mean_std(I)

Get mean and standard deviation of each channel.

Parameters:I – Image RGB uint8. Returns:

static lab_split(I)

Convert from RGB uint8 to LAB and split into channels.

Parameters:I – Image RGB uint8. Returns:

static merge_back(I1, I2, I3)

Take seperate LAB channels and merge back to give RGB uint8.

Parameters:

• I1 – L
• I2 – A
• I3 – B

Returns:

Image RGB uint8.

transform(I)

Transform an image.

Parameters:I – Image RGB uint8. Returns:

Macenko method

class staintools.normalization.macenko.MacenkoNormalizer(**kwargs)

Stain normalization based on the method of: M. Macenko et al., ‘A method for normalizing histology slides for quantitative analysis’, in 2009 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, 2009, pp. 1107–1110.

fit(target)

Fit to a target image.

Parameters:target – Image RGB uint8. Returns:

static get_stain_matrix(I, beta=0.15, alpha=1)

Get the stain matrix (2x3). First row H and second row E. See the original paper for details.

Parameters:

• I – Image RGB uint8.
• beta –
• alpha –

Returns:

transform(I)

Transform an image.

Parameters:I – Image RGB uint8. Returns:

Vahadane method

class staintools.normalization.vahadane.VahadaneNormalizer(**kwargs)

Stain normalization inspired by method of: A. Vahadane et al., ‘Structure-Preserving Color Normalization and Sparse Stain Separation for Histological Images’, IEEE Transactions on Medical Imaging, vol. 35, no. 8, pp. 1962–1971, Aug. 2016.

static get_stain_matrix(I, threshold=0.8, lamda=0.1)

Get 2x3 stain matrix. First row H and second row E. See the original paper for details. Also see spams docs.

Parameters:

• I – Image RGB uint8.
• threshold –
• lamda –

Returns:

Utils

Visualization Utils

Visualization utilities.

staintools.utils.visual.build_stack(images)

Build a stack of images from a tuple/list of images.

Parameters:images – A tuple/list of images. Returns:

staintools.utils.visual.patch_grid(ims, width=5, sub_sample=False, rand=False, save_name=None)

Display a grid of patches.

Parameters:

• ims – A patch ‘stack’
• width – Images per row.
• sub_sample – Should we take a subsample?
• rand – Randomize subsample?

Returns:

staintools.utils.visual.read_image(path)

Read an image to RGB uint8. Read with opencv (cv) and covert from BGR colorspace to RGB.

Parameters:path – The path to the image. Returns:RGB uint8 image.

staintools.utils.visual.show(image, now=True, fig_size=(10, 10))

Show an image (np.array). Caution! Rescales image to be in range [0,1].

Parameters:

• image –
• now – plt.show() now?
• fig_size – Figure size.

Returns:

staintools.utils.visual.show_colors(C)

Visualize rows of C as colors (RGB)

Parameters:C – An array N x 3 where the rows are considered as RGB colors. Returns:

Misc Utils

Other utilities.

staintools.utils.misc.OD_to_RGB(OD)

Convert from optical density (OD_RGB) to RGB RGB = 255 * exp(-1*OD_RGB)

Parameters:OD – Optical denisty RGB image. Returns:Image RGB uint8.

staintools.utils.misc.RGB_to_OD(I)

Convert from RGB to optical density (OD_RGB) space. RGB = 255 * exp(-1*OD_RGB).

Parameters:I – Image RGB uint8. Returns:Optical denisty RGB image.

staintools.utils.misc.array_equal(A, B, eps=1e-09)

Are arrays A and B equal?

Parameters:

• A – Array.
• B – Array.
• eps – Tolerance.

Returns:

True/False.

staintools.utils.misc.check_image(x)

Check if is an image. If gray make sure it is ‘squeezed’ correctly.

Parameters:x – Input. Returns:True/False.

staintools.utils.misc.is_gray_image(x)

Is x a gray image?

Parameters:x – Input. Returns:True/False.

staintools.utils.misc.is_image(x)

Is x an image? i.e. numpy array of 2 or 3 dimensions.

Parameters:x – Input. Returns:True/False.

staintools.utils.misc.is_uint8_image(x)

Is x a uint8 image?

Parameters:x – Input. Returns:True/False.

staintools.utils.misc.normalize_rows(A)

Normalize the rows of an array.

Parameters:A – An array. Returns:Array with rows normalized.

staintools.utils.misc.notwhite_mask(I, thresh=0.8)

Get a binary mask where true denotes ‘not white’. Specifically, a pixel is not white if its luminance (in LAB color space) is less than the specified threshold.

Parameters:

• I – RGB uint 8 image.
• thresh – Luminosity threshold.

Returns:

Binary mask where true denotes ‘not white’.

staintools.utils.misc.remove_zeros(I)

Remove zeros in an image, replace with 1’s.

Parameters:I – An Array. Returns:New array where 0’s have been replaced with 1’s.

staintools.utils.misc.sign(x)

Returns the sign of x.

Parameters:x – A scalar x. Returns:The sign of x in (+1, -1, 0).

staintools.utils.misc.standardize_brightness(I, percentile=95)

Standardize brightness.

Parameters:I – Image uint8 RGB. Returns:Image uint8 RGB with standardized brightness.

Indices and tables

• Index
• Module Index
• Search Page