On 8/17/06, Christopher Barker <[EMAIL PROTECTED]> wrote:
> Hi all,
>
> I seem to be talking to myself here, but if someone (including myself)
> wants to pick this up in the future, it'll be good to have it in the
> archives.
>
> Christopher Barker wrote:
> >> There is also the
> >> wx.Image.SetDataBuffer method, which will have the wxImage use the
> >> buffer passed in without making a copy, but if the buffer doesn't
> >> live as long as the image does it will likely cause a crash.
> >
> > This would probably be the easiest way to get top performance at the
> > moment. If we can make the Agg data a buffer, and somehow do the
> > reference counting right so it doesn't get deleted while the wxImage is
> > still around (that may not be hard -- the wxImage has to be converted to
> > a wxBitmap to be drawn anyway)
>
> I've been suing this for another use, and Robin just added an improved
> version of new wx.Image factory function I wrote for just this purpose:
>
> def ImageFromBuffer(width, height, dataBuffer, alphaBuffer=None):
> """
> Creates a `wx.Image` from the data in dataBuffer. The dataBuffer
> parameter must be a Python object that implements the buffer
> interface, such as a string, array, etc. The dataBuffer object is
> expected to contain a series of RGB bytes and be width*height*3
> bytes long. A buffer object can optionally be supplied for the
> image's alpha channel data, and it is expected to be width*height
> bytes long.
>
> A reference to the data and alpha buffer objects are kept with the
> wx.Image, so that they won't get deleted until after the wx.Image
> is deleted. However please be aware that it is not guaranteed that
> an object won't move its memory buffer to a new location when it
> needs to resize its contents. If that happens then the wx.Image
> will end up referring to an invalid memory location and could cause
> the application to crash. Therefore care should be taken to not
> manipulate the objects used for the data and alpha buffers in a
> way that would cause them to change size.
> """
> image = wx.EmptyImage(width, height)
> image.SetDataBuffer(dataBuffer)
> if alphaBuffer is not None:
> image.SetAlphaBuffer(alphaBuffer)
> image._buffer = dataBuffer
> image._alpha = alphaBuffer
> return image
>
> Does the aggDrawer already implement a Python buffer object? If so,
> using this would be easy. If not, then it probably should, unless we go
> straight to the numpy array protocol.
I haven't had time to thoroughly absorb all your post. From skimming
it looks like we could do a similar approach as the qtagg blitting.
If you look at the else clause in the FigureCanvasQTAgg.paintEvent
method, you'll see we added a to_string method to the BufferRegion
object. Using this string buffer we create a QImage and blit it. It
includes the alpha channel. I'll paste the block of interest to save
you a little digging.
bbox = self.replot
w, h = int(bbox.width()), int(bbox.height())
l, t = bbox.ll().x().get(), bbox.ur().y().get()
reg = self.copy_from_bbox(bbox)
stringBuffer = reg.to_string()
qImage = qt.QImage(stringBuffer, w, h, 32, None, 0,
qt.QImage.IgnoreEndian)
self.pixmap.convertFromImage(qImage, qt.QPixmap.Color)
p.drawPixmap(qt.QPoint(l, self.renderer.height-t), self.pixmap)
- Charlie
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