Add short description of example

Author: j9ac9k

doc/source/api_reference/graphicsItems/imageitem.rst

@@ -24,19 +24,19 @@ individual :python:`[R,G,B]` or :python:`[R,G,B,A]` channels/components.
 Notes
 -----
 
+:class:`~pyqtgraph.ImageItem` is frequently used in conjunction with
+:class:`~pyqtgraph.ColorBarItem` to provide a color map display and interactive level
+adjustments, or with :class:`~pyqtgraph.HistogramLUTItem` or
+:class:`~pyqtgraph.HistogramLUTWidget` for a full GUI to control the levels and lookup
+table used to display the image.
+
 An image can be placed into a plot area of a given extent directly through the
 :meth:`ImageItem.setRect <pyqtgraph.ImageItem.setRect>` method or the ``rect`` keyword.
 This is internally realized through assigning a :class:`QTransform`. For other
 translation, scaling or rotations effects that persist for all later image data, the
 user can also directly define and assign such a transform, as shown in the example
 below.
 
-:class:`~pyqtgraph.ImageItem` is frequently used in conjunction with
-:class:`~pyqtgraph.ColorBarItem` to provide a color map display and interactive level
-adjustments, or with :class:`~pyqtgraph.HistogramLUTItem` or
-:class:`~pyqtgraph.HistogramLUTWidget` for a full GUI to control the levels and lookup
-table used to display the image.
-
 Performance
 -----------
 
@@ -53,8 +53,8 @@ The following guidance should be observed if performance is an important factor
     :python:`pyqtgraph.setConfigOption('imageAxisOrder', 'row-major')`
 
 * Use C-contiguous image data.
-* For 1 or 3 channel data, use `uint8`, `uint16`, `float32`, or `float64` 
-  ``image`` dtype.
+* For 1 or 3 channel data, use `uint8`, `uint16`, `float32`, or `float64` ``image``
+  dtype.
 * For 4-channel data, use `uint8` or `uint16` with :python:`levels=None`.
 * ``levels`` should be set to (even if to ``None``) to avoid autoLevels sampling.
 * ``levels`` should be single channel or ``None``.
@@ -65,8 +65,8 @@ The following guidance should be observed if performance is an important factor
   * :func:`ImageItem.setLookupTable <pyqtgraph.ImageItem.setLookupTable>` with 
     :python:`ColorMap.getLookupTable(nPts=256)` (default is :python:`nPts=512`)
 
-* For floating point ``image`` arrays, prefer `float32` dtype to `float64`
-  and avoid ``NaN`` values.
+* For floating point ``image`` arrays, prefer `float32` dtype to `float64` and avoid
+  ``NaN`` values.
 * Enable Numba with :python:`pyqtgraph.setConfigOption('useNumba', True)`
 
   * JIT compilation will only accelerate repeated image display.
@@ -89,6 +89,10 @@ do not call :func:`~pyqtgraph.functions.makeARGB`.
 Examples
 --------
 
+In the following example, it is demonstrated how a user scale and translate a
+:class:`~pyqtgraph.ImageItem` within a :class:`~pyqtgraph.ViewBox` to occupy a specific
+position and size.
+
 .. literalinclude:: /images/gen_example_imageitem_transform.py
     :lines: 19-28
     :dedent: 8