Question

I am learning wxPython. My question is how create bit map. I have R, G, B values for each pixel but I don’t know how create bit map from it. I tried use wx.BitmapFromBuffer, I don’t understand how should I create this buffer. I went through each pixel and in linear way put in list R, G, B components, but it did not draw what I expected. Do you understand how the buffer should be constructed?.

I don’t want draw each pixel on bitmap using wx.MemoryDC because it is too slow.

Thank you!

Edit:
I use approach from wxPython demo – RawBitmapAccess.

    buf = numpy.empty((w,h,3), numpy.uint8)
    n = 29000
    for i in xrange(w):
        for j in xrange(h):
            r = int(n*255*field[j,i])
            if r > 253: 
                r = 253
            buf[i, j, 0] = int(r)
            buf[i, j, 1] = int(r)
            buf[i, j, 2] = int(b)
            #dc.SetPen(wx.Pen(wx.Colour(r,r,b)))
            #dc.DrawPoint(i,j)
    bmp = wx.BitmapFromBuffer(w, h, buf)
    gc = wx.GraphicsContext.Create(dc)
    gc.DrawBitmap(bmp, 0, 0, w, h)

If I uncomment my old way of drawing (two commented lines in the loop) then I got what I want – one fuzzy ball. If I don’t uncomment them that I have odd picture – it is splitted vertically for several fragments, each have it own fuzzy ball, plus it look like that there is vertical lines of missed pixels.
I use buffer in the same way as in demo program. Why I get weird picture?

Edit2:
I figure out it. I should swap i and j in the loop.

Answer 1

As I posted in my previous answer, this is done using numpy, and there’s an example in the demo call RawBitmapAccess. The code basically looks like,

def MakeBitmap2(self, red, green, blue, alpha=128):
    # Make an array of bytes that is DIM*DIM in size, with enough
    # slots for each pixel to have a RGB and A value
    #arr = makeByteArray( (DIM,DIM, 4) )
    arr = numpy.empty((DIM,DIM, 4), numpy.uint8)

    # just some indexes to keep track of which byte is which
    R, G, B, A = range(4)

    # initialize all pixel values to the values passed in
    arr[:,:,R] = red
    arr[:,:,G] = green
    arr[:,:,B] = blue
    arr[:,:,A] = alpha

    # Set the alpha for the border pixels to be fully opaque
    arr[0,     0:DIM, A] = wx.ALPHA_OPAQUE  # first row
    arr[DIM-1, 0:DIM, A] = wx.ALPHA_OPAQUE  # last row
    arr[0:DIM, 0,     A] = wx.ALPHA_OPAQUE  # first col
    arr[0:DIM, DIM-1, A] = wx.ALPHA_OPAQUE  # last col

    # finally, use the array to create a bitmap
    bmp = wx.BitmapFromBufferRGBA(DIM, DIM, arr)
    return bmp