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For a 2D image,`px.imshow` uses a colorscale to map scalar data to colors. The default colorscale is the one of the active template (see[the tutorial on templates](/python/templates/)).

For a 2D image,`px.imshow` uses a colorscale to map scalar data to colors. The default colorscale is the one of the active template (see[the tutorial on templates](/python/templates/)).

import plotly.expressas px

It is also possible to use the`go.Image` trace from the low-level`graph_objects` API in order to display image data. Note that`go.Image` only accepts multichannel images. For single images, use[`go.Heatmap`](/python/heatmaps).

Note that the`go.Image` trace is different from the`go.layout.Image` class, which can be used for[adding background images or logos to figures](/python/images).

Note that the`go.Image` trace is different from the`go.layout.Image` class, which can be used for[adding background images or logos to figures](/python/images).

import plotly.graph_objectsas go

The data range and color range are mapped together using the parameters`zmin` and`zmax`, which correspond respectively to the data values mapped to black`[0, 0, 0]` and white`[255, 255, 255]`, or to the extreme colors of the colorscale in the case on single-channel data.

The data range and color range are mapped together using the parameters`zmin` and`zmax`, which correspond respectively to the data values mapped to black`[0, 0, 0]` and white`[255, 255, 255]`, or to the extreme colors of the colorscale in the case on single-channel data.

For single-channel data, the defaults values of`zmin` and`zmax` used by`px.imshow` and`go.Heatmap` are the extrema of the data range. For multichannel data,`px.imshow` and`go.Image` use slightly different default values for`zmin` and`zmax`. For`go.Image`, the default value is`zmin=[0, 0, 0]` and`zmax=[255, 255, 255]`, no matter the data type. On the other hand,`px.imshow` adapts the default`zmin` and`zmax` to the data type:

- for integer data types,`zmin` and`zmax` correspond to the extreme values of the data type, for example 0 and 255 for`uint8`, 0 and 65535 for`uint16`, etc.

from skimageimport data

img= data.camera()

fig= px.imshow(img,color_continuous_scale='gray')

fig.add_trace(go.Contour(z=img,showscale=False,

fig.add_trace(go.Contour(z=img,showscale=False,

contours=dict(start=0,end=70,size=70,coloring='lines'),

line_width=2))

fig.add_trace(go.Scatter(x=[230],y=[100],marker=dict(color='red',size=16)))

fig.add_trace(go.Image(z=img),1,1)

for channel, colorinenumerate(['red','green','blue']):

fig.add_trace(go.Histogram(x=img[..., channel].ravel(),opacity=0.5,

fig.add_trace(go.Histogram(x=img[..., channel].ravel(),opacity=0.5,

marker_color=color,name='%s channel'%color),1,2)

fig.update_layout(height=400)

fig.show()