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Merged
merged 12 commits into from
Nov 12, 2019
Merged

new tutorial on displaying image data #163

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cfac436
new tutorial on displaying image data
emmanuelle Nov 1, 2019
2056d13
minor changes
emmanuelle Nov 5, 2019
10d64b9
minor changes
emmanuelle Nov 6, 2019
4654c06
updated how to disable ticks
emmanuelle Nov 6, 2019
f97dfc4
zmax update
emmanuelle Nov 7, 2019
4f3bc89
new tutorial on displaying image data
emmanuelle Nov 1, 2019
67c1830
minor changes
emmanuelle Nov 5, 2019
cc59b3c
minor changes
emmanuelle Nov 6, 2019
9d01e29
updated how to disable ticks
emmanuelle Nov 6, 2019
4e93741
zmax update
emmanuelle Nov 7, 2019
7696258
Merge branch 'image' of https://github.com/plotly/plotly.py-docs into…
emmanuelle Nov 12, 2019
bd06f3b
fix color_continuous_scale
emmanuelle Nov 12, 2019
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zmax update
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@emmanuelle
emmanuelle committed Nov 7, 2019
commit f97dfc40bad7acf84b9f6a7a27dcd81efb709ecd
12 changes: 8 additions & 4 deletions python/imshow.md
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Expand Up @@ -82,7 +82,7 @@ For a 2D image, `px.imshow` uses a colorscale to map scalar data to colors. The
```python
import plotly.express as px
import numpy as np
img = np.arange(100).reshape((10, 10))
img = np.arange(15**2).reshape((15, 15))
fig = px.imshow(img)
fig.show()
```
Expand Down Expand Up @@ -116,11 +116,11 @@ fig.show()

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.

`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 single-channel data, the defaults values of `zmin` and `zmax` used by `px.imshow` and `go.Heatmap` are the 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.
- for float numbers, when the data range is more arbitrary, the minimum and maximum values of the image (across all channels) is used.
- for float numbers, the maximum value of the data is computed, and zmax is 1 if the max is smaller than 1, 255 if the max is smaller than 255, etc. (with higher thresholds 2**16 - 1 and 2**32 -1).

These defaults can be overriden by setting the values of `zmin` and `zmax`. For `go.Image`, `zmin` and `zmax` need to be given for all channels, whereas it is also possible to pass a scalar value (used for all channels) go `px.imshow`.
These defaults can be overriden by setting the values of `zmin` and `zmax`. For `go.Image`, `zmin` and `zmax` need to be given for all channels, whereas it is also possible to pass a scalar value (used for all channels) to `px.imshow`.

```python
import plotly.express as px
Expand Down Expand Up @@ -189,3 +189,7 @@ fig.show()
#### Reference
See https://plot.ly/python/reference/#image for more information and chart attribute options!


```python
fig = px.imshow
```