***********
wx.MemoryDC
***********

Inheritance diagram for `wx.MemoryDC`:

|

.. inheritance-diagram:: wx.MemoryDC

|

Description
===========

A memory device context provides a means to draw graphics onto a bitmap. When drawing in to a mono-bitmap, using 
``wx.WHITE``, ``wx.WHITE_PEN`` and ``wx.WHITE_BRUSH`` will draw the background colour (i.e. 0) whereas all other 
colours will draw the foreground colour (i.e. 1).


.. seealso:: `wx.Bitmap <wx.Bitmap.html>`_, `wx.DC <wx.DC.html>`_


Derived From
^^^^^^^^^^^^^

* `wx.DC <wx.DC.html>`_ 
* `wx.Object <wx.Object.html>`_ 


Known Subclasses
^^^^^^^^^^^^^^^^

`wx.BufferedDC <wx.BufferedDC.html>`_, `wx.BufferedPaintDC <wx.BufferedPaintDC.html>`_

Remarks
^^^^^^^

A bitmap must be selected into the new memory DC before it may be used for anything.  

Typical usage is as follows::


    # Create a memory DC   
    temp_dc = wx.MemoryDC()
    temp_dc.SelectObject(test_bitmap)

    # We can now draw into the memory DC...   
    DrawSomething(temp_dc)

    # Copy from this DC to another DC.   
    old_dc.Blit(250, 50, BITMAP_WIDTH, BITMAP_HEIGHT, temp_dc, 0, 0) 

    temp_dc.SelectObject(wx.NullBitmap)


.. note:: Note that the memory DC **must** be deleted (or the bitmap selected out of it) before a bitmap can be reselected 
   into another memory DC.


Methods Summary
^^^^^^^^^^^^^^^

* `__init__ <#__init__>`_ 
* `SelectObject <#SelectObject>`_ 
* `SelectObjectAsSource <#SelectObjectAsSource>`_ 

Class API
=========

Methods
^^^^^^^


.. method:: __init__(bitmap=wx.NullBitmap)

   Constructs a new memory device context.
   
   Use the `Ok` member to test whether the constructor was successful in
   creating a usable device context. If a bitmap is not given to this
   constructor then don't forget to select a bitmap into the DC before
   drawing on it.
   
   **Parameters:**

   * `bitmap` (`wx.Bitmap <wx.Bitmap.html>`_)

   |

   **Returns:**

   `wx.MemoryDC <wx.MemoryDC.html>`_
 

--------

.. method:: SelectObject(bitmap)

   Works exactly like `SelectObjectAsSource <#SelectObjectAsSource>`_ but this is the function you should use when you select a 
   bitmap because you want to modify it, e.g. drawing on this DC.

   Be careful to use this function and not `SelectObjectAsSource <#SelectObjectAsSource>`_ when you want to modify the bitmap 
   you are selecting otherwise you may incurr in some problems related to `wx.Bitmap` being a reference counted object.

   **Parameters:**

   * `bitmap` (`wx.Bitmap <wx.Bitmap.html>`_) 


.. seealso:: `wx.DC.DrawBitmap <wx.DC.html#DrawBitmap>`_
  

--------

.. method:: SelectObjectAsSource(bitmap)

   Selects the given bitmap into the device context, to use as the memory bitmap. Selecting the bitmap into a memory DC allows you 
   to draw into the DC (and therefore the bitmap) and also to use `wx.DC.Blit <wx.DC.html#Blit>`_ to copy the bitmap to a window. 
   For this purpose, you may find `wx.DC.DrawIcon <wx.DC.html#DrawIcon>`_ easier to use instead.

   If the argument is `wx.NullBitmap` (or some other uninitialised `wx.Bitmap`) the current bitmap is selected out of the device context, 
   and the original bitmap restored, allowing the current bitmap to be destroyed safely.

   **Parameters:**

   * `bitmap` (`wx.Bitmap <wx.Bitmap.html>`_) 


.. seealso:: `SelectObject <#SelectObject>`_