matplotlib.axes.Axes.imshow#

Axes.imshow(X, cmap=None, norm=None, *, aspect=None, interpolation=None, alpha=None, vmin=None, vmax=None, colorizer=None, origin=None, extent=None, interpolation_stage=None, filternorm=True, filterrad=4.0, resample=None, url=None, data=None, **kwargs)[source]#

Display data as an image, i.e., on a 2D regular raster.

The input may either be actual RGB(A) data, or 2D scalar data, which will be rendered as a pseudocolor image. For displaying a grayscale image, set up the colormapping using the parameters cmap='gray', vmin=0, vmax=255.

The number of pixels used to render an image is set by the Axes size and the figure dpi. This can lead to aliasing artifacts when the image is resampled, because the displayed image size will usually not match the size of X (see Image resampling). The resampling can be controlled via the interpolation parameter and/or rcParams["image.interpolation"] (default: 'auto').

Parameters:

Xarray-like or PIL image

The image data. Supported array shapes are:

(M, N): an image with scalar data. The values are mapped to colors using normalization and a colormap. See parameters norm, cmap, vmin, vmax.
(M, N, 3): an image with RGB values (0-1 float or 0-255 int).
(M, N, 4): an image with RGBA values (0-1 float or 0-255 int), i.e. including transparency.

The first two dimensions (M, N) define the rows and columns of the image.

Out-of-range RGB(A) values are clipped.

cmapstr or Colormap, default: rcParams["image.cmap"] (default: 'viridis')

The Colormap instance or registered colormap name used to map scalar data to colors.

This parameter is ignored if X is RGB(A).

normstr or Normalize, optional

The normalization method used to scale scalar data to the [0, 1] range before mapping to colors using cmap. By default, a linear scaling is used, mapping the lowest value to 0 and the highest to 1.

If given, this can be one of the following:

An instance of Normalize or one of its subclasses (see Colormap normalization).
A scale name, i.e. one of "linear", "log", "symlog", "logit", etc. For a list of available scales, call matplotlib.scale.get_scale_names(). In that case, a suitable Normalize subclass is dynamically generated and instantiated.

This parameter is ignored if X is RGB(A).

vmin, vmaxfloat, optional

When using scalar data and no explicit norm, vmin and vmax define the data range that the colormap covers. By default, the colormap covers the complete value range of the supplied data. It is an error to use vmin/vmax when a norm instance is given (but using a str norm name together with vmin/vmax is acceptable).

This parameter is ignored if X is RGB(A).

colorizerColorizer or None, default: None

The Colorizer object used to map color to data. If None, a Colorizer object is created from a norm and cmap.

This parameter is ignored if X is RGB(A).

aspect{'equal', 'auto'} or float or None, default: None

The aspect ratio of the Axes. This parameter is particularly relevant for images since it determines whether data pixels are square.

This parameter is a shortcut for explicitly calling Axes.set_aspect. See there for further details.

'equal': Ensures an aspect ratio of 1. Pixels will be square (unless pixel sizes are explicitly made non-square in data coordinates using extent).
'auto': The Axes is kept fixed and the aspect is adjusted so that the data fit in the Axes. In general, this will result in non-square pixels.

Normally, None (the default) means to use rcParams["image.aspect"] (default: 'equal'). However, if the image uses a transform that does not contain the axes data transform, then None means to not modify the axes aspect at all (in that case, directly call Axes.set_aspect if desired).

interpolationstr, default: rcParams["image.interpolation"] (default: 'auto')

The interpolation method used.

Supported values are 'none', 'auto', 'nearest', 'bilinear', 'bicubic', 'spline16', 'spline36', 'hanning', 'hamming', 'hermite', 'kaiser', 'quadric', 'catrom', 'gaussian', 'bessel', 'mitchell', 'sinc', 'lanczos', 'blackman'.

The data X is resampled to the pixel size of the image on the figure canvas, using the interpolation method to either up- or downsample the data.

If interpolation is 'none', then for the ps, pdf, and svg backends no down- or upsampling occurs, and the image data is passed to the backend as a native image. Note that different ps, pdf, and svg viewers may display these raw pixels differently. On other backends, 'none' is the same as 'nearest'.

If interpolation is the default 'auto', then 'nearest' interpolation is used if the image is upsampled by more than a factor of three (i.e. the number of display pixels is at least three times the size of the data array). If the upsampling rate is smaller than 3, or the image is downsampled, then 'hanning' interpolation is used to act as an anti-aliasing filter, unless the image happens to be upsampled by exactly a factor of two or one.

See Interpolations for imshow for an overview of the supported interpolation methods, and Image resampling for a discussion of image antialiasing.

Some interpolation methods require an additional radius parameter, which can be set by filterrad. Additionally, the antigrain image resize filter is controlled by the parameter filternorm.

interpolation_stage{'auto', 'data', 'rgba'}, default: 'auto'

Supported values:

'data': Interpolation is carried out on the data provided by the user This is useful if interpolating between pixels during upsampling.
'rgba': The interpolation is carried out in RGBA-space after the color-mapping has been applied. This is useful if downsampling and combining pixels visually.
'auto': Select a suitable interpolation stage automatically. This uses 'rgba' when downsampling, or upsampling at a rate less than 3, and 'data' when upsampling at a higher rate.

See Image resampling for a discussion of image antialiasing.

alphafloat or array-like, optional

The alpha blending value, between 0 (transparent) and 1 (opaque). If alpha is an array, the alpha blending values are applied pixel by pixel, and alpha must have the same shape as X.

origin{'upper', 'lower'}, default: rcParams["image.origin"] (default: 'upper')

Place the [0, 0] index of the array in the upper left or lower left corner of the Axes. The convention (the default) 'upper' is typically used for matrices and images.

Note that the vertical axis points upward for 'lower' but downward for 'upper'.

See the origin and extent in imshow tutorial for examples and a more detailed description.

extentfloats (left, right, bottom, top), optional

The bounding box in data coordinates that the image will fill. These values may be unitful and match the units of the Axes. The image is stretched individually along x and y to fill the box.

The default extent is determined by the following conditions. Pixels have unit size in data coordinates. Their centers are on integer coordinates, and their center coordinates range from 0 to columns-1 horizontally and from 0 to rows-1 vertically.

Note that the direction of the vertical axis and thus the default values for top and bottom depend on origin:

For origin == 'upper' the default is (-0.5, numcols-0.5, numrows-0.5, -0.5).
For origin == 'lower' the default is (-0.5, numcols-0.5, -0.5, numrows-0.5).

See the origin and extent in imshow tutorial for examples and a more detailed description.

filternormbool, default: True

A parameter for the antigrain image resize filter (see the antigrain documentation). If filternorm is set, the filter normalizes integer values and corrects the rounding errors. It doesn't do anything with the source floating point values, it corrects only integers according to the rule of 1.0 which means that any sum of pixel weights must be equal to 1.0. So, the filter function must produce a graph of the proper shape.

filterradfloat > 0, default: 4.0

The filter radius for filters that have a radius parameter, i.e. when interpolation is one of: 'sinc', 'lanczos' or 'blackman'.

resamplebool, default: rcParams["image.resample"] (default: True)

When True, use a full resampling method. When False, only resample when the output image is larger than the input image.

urlstr, optional

Set the url of the created AxesImage. See Artist.set_url.

Returns:

AxesImage

Other Parameters:

dataindexable object, optional: If given, all parameters also accept a string s, which is interpreted as data[s] if s is a key in data.
**kwargsArtist properties: These parameters are passed on to the constructor of the AxesImage artist.