[wxPython-users] graphics class definitions

[Christopher Barker]

Karl Kobata wrote:
> Will someone explain if the DC subclasses stores data as bmp or vector
> graphics?

not a simple answer....

> It seems that wx.MemoryDC specifically says graphics are stored it bitmap
> form, but the others do not.  So does this mean, wx.ClientDC, wx.PaintDC,
> wx.PrinterDC, wx.ScreenDC, wx.WindowDC, and wx.GraphicsContext store
> graphics in vector format?

No, it means that they don't store the graphics at all. They are 
renderers -- they render both vector and bitmap graphics to various 
devices in various ways. A wx.MemoryDC renders to a wx.Bitmap object 
(which then can store the result as a bitmap), the wx.clientDC, 
wx.PaintDC, wx.ScreenDC all render to the screen, and don't store 
anything themselves. The wx.PrinterDC renders to the printer device, and 
doesn't store anything.

a wx.GraphicsContext is a similar concept -- it is a rendering interface 
that can render to various different things. It is similar to a DC, 
except that it is newer and more sophisticated. It's a bit harder to 
use, can have poorer performance, but give additional capabilities, 
notably real alpha blending and anti-aliasing.

See:
http://wiki.wxpython.org/RecipesImagesAndGraphics?highlight=%28graphics%29

for some background.

-Chris

PS: FloatCanvas stores drawings as vector data and handles zooming, etc 
for you. It does its actual rendering with DCs, though it can optionally 
use GraphicsContext.



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