Hi Johannes,
According to http://www.pygtk.org/pygtk2reference/class-
gdkpixbuf.html , the pixels_array is a numeric python array (a
predecessor to numpy). The upshot is that perhaps the nice
broadcasting machinery will work fine:
pb_pixels[...] = fits_pixels[..., numpy.newaxis]
This might not work, though. But perhaps it would be possible to make
a numpy array that's really just a view onto the memory of pb_pixels,
or perhaps one could convert fits_pixels into a numeric array...
Hopefully someone on the list can make a suggestion about dealing with
numeric arrays.
Alternately, there are pixbuf methods for reading image data from
strings. You'd just need to get fits_pixels set up properly, then call
tostring() on it, and pass that to the pixbuf. The trick is in setting
up fits_pixels so that its memory layout corresponds to what gtk
wants. Usually, images are stored in memory as (r,g,b) tuples packed
by rows and then columns; this is I assume what GTK wants. So you'd do
something like:
fits_color = numpy.empty((height, width, 3), dtype=numpy.uint8)
fits_color[...] = fits_pixels[..., numpy.newaxis]
fits_string = fits_color.tostring()
pb = gtk.gdk.pixbuf_new_from_data(fits_string, gtk.gdk.COLORSPACE_RGB,
False, 8, 640, 480, 3*640)
Zach
On Apr 28, 2009, at 2:36 AM, Johannes Bauer wrote:
Hello group,
I've been redicted from usenet (Convert numpy.ndarray into normal
array, 75dgm1f16hqn...@mid.dfncis.de) here and hope this is the
right
place.
Basically, what I have is a numpy-Array which I got from a FITS-file
(it's black/white). I want to display that using GTK. Therefore every
color needs to appear three times (to make it look gray R = G = B).
The basic framework looks like
[...]
pb = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB, False, 8, width, height)
pb_pixels = pb.get_pixels_array()
print(type(pb_pixels), pb_pixels.shape, pb_pixels.typecode())
print(type(fits_pixels), fits_pixels.shape, fits_pixels.dtype)
which gives
(type 'array', (480, 640, 3), 'b')
(type 'numpy.ndarray', (480, 640), dtype('uint8'))
so now I need to assign values. Naively I started out with
for x in range(width):
for y in range(height):
pb_pixels[y, x] = fits_pixels[y, x]
which was horribly slow (around 3 seconds). Thanks to the usenet
help, I
now got somewhat better:
fits_colors = numpy.zeros((height, width, 3), dtype=uint8)
for y in range(height):
for x in range(width):
fits_colors[height - y - 1, x] = fits_pixels[y, x]
pb_pixels[:, :] = fits_colors
This also works, and is a lot faster (around 0.7 seconds). However,
there seems to be a better way to do it. I played around with
fits_colors = numpy.fromfunction(lambda y, x, z: fits_pixels[y, x],
(height, width, 3), dtype=uint8)
pb_pixels[:, :] = fits_colors
Which worked somewhat - but gives weird results: The picture is
rotatated 90° to the right and the lower left part is displayed
repeatedly after 256 pixels... (I can make a screenshot if that's
easier). The fromfunction Function is quite fast in my context (around
0.2 second).
How should I solve this problem the right way?
Kind regards,
Johannes
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