viewing rotated pixels possible with mpl?

Hi, this is a question I have posted earlier, but

    > unfortunately I didn't get any answer. if anybody has any
    > hint on how to do this, I would be most graceful!! Thanks
    > in advance!

I looked at this a bit -- the underlying image extension code handles
image rotations but it is not exposed at the python level. I spent
some time working on an image class that would handle rotations (in
this test code below I just hardcoded the rotation for testing). The
missing part is to get the extent and image placement algorithms to do
the layout properly in the presence of rotation (eg handling extent
and corners properly below). But this should give the enterprising
developer a head start if they want to run with with. Basically, I
just copied the guts out of the axes.image.AxesImage.make_image code
to experiment with adding a rotation

from matplotlib.image import AxesImage
from pylab import subplot, show, nx

class RotatedImage(AxesImage):
    def make_image(self):
        from matplotlib.colors import normalize, colorConverter
        from matplotlib.numerix import arange, asarray, UInt8, Float32, repeat, NewAxis, typecode
        import matplotlib._image as _image

        if self._A is not None:
            if self._imcache is None:
                if typecode(self._A) == UInt8:
                    im = _image.frombyte(self._A, 0)
                    im.is_grayscale = False
                    x = self.to_rgba(self._A, self._alpha)
                    im = _image.fromarray(x, 0)
                    if len(self._A.shape) == 2:
                        im.is_grayscale = self.cmap.is_gray()
                        im.is_grayscale = False
                self._imcache = im
                im = self._imcache
            raise RuntimeError('You must first set the image array or the image attribute')

        bg = colorConverter.to_rgba(self.axes.get_frame().get_facecolor(), 0)

        if self.origin=='upper':

        im.set_bg( *bg)


        # image input dimensions
        numrows, numcols = im.get_size()

        xmin, xmax, ymin, ymax = self.get_extent()
        dxintv = xmax-xmin
        dyintv = ymax-ymin

        # the viewport scale factor
        sx = dxintv/self.axes.viewLim.width()
        sy = dyintv/self.axes.viewLim.height()

        if im.get_interpolation()!=_image.NEAREST:
            im.apply_translation(-1, -1)

        # the viewport translation
        tx = (xmin-self.axes.viewLim.xmin())/dxintv * numcols

        #if flipy:
        # ty = -(ymax-self.axes.viewLim.ymax())/dyintv * numrows
        # ty = (ymin-self.axes.viewLim.ymin())/dyintv * numrows
        ty = (ymin-self.axes.viewLim.ymin())/dyintv * numrows

        l, b, widthDisplay, heightDisplay = self.axes.bbox.get_bounds()

        im.apply_translation(tx, ty)
        im.apply_scaling(sx, sy)

        # resize viewport to display
        rx = widthDisplay / numcols
        ry = heightDisplay / numrows
        im.apply_scaling(rx, ry)
        #print tx, ty, sx, sy, rx, ry, widthDisplay, heightDisplay
        im.resize(int(widthDisplay+0.5), int(heightDisplay+0.5),
                  norm=self._filternorm, radius=self._filterrad)

        if self.origin=='upper':

        return im

ax = subplot(111)

im = RotatedImage(ax, interpolation='nearest')

xmin, xmax, ymin, ymax = im.get_extent()

corners = (xmin, ymin), (xmax, ymax)
ax.set_xlim((xmin, xmax))
ax.set_ylim((ymin, ymax))



I was in the meantime working out something using the suggestion Eric
sent me (e.g. via pcolormesh) and I could work most of things I wanted
out, but at the price of a rather stupidly looking management of the
axis and rotation (maybe there is a way for improvement here too…).

Your solution may indeed be a cleaner way forward! I’ll try both ways
and see how I manage to get things done (the main problem being my
rather poor ability in writing advanced codes in python…

thanks &



John Hunter wrote:



                           -- ====================================================================
Eric Emsellem Centre de Recherche Astrophysique de Lyon
9 av. Charles-Andre tel: +33 (0)4 78 86 83 84
69561 Saint-Genis Laval Cedex fax: +33 (0)4 78 86 83 86
France ====================================================================