[Matplotlib-users] GTK antialised rendering, visuals, Pixbuf

[Trevor B. <tl...@an...>]

In backend_gtk.py, it does some antialiased rendering by direct
manipulation of pixel values which is only correct for 24-bit TrueColor
X11 visuals. I'm running a 16-bit (5 red, 6 green, 5 blue) visual, so
this produces visual junk.

I think the right way to do it is with a Pixbuf, which handles alpha
rendering. The code is much simpler and faster too. Here is a patch:

(This is from matplotlib-0.51.)

--- backends/backend_gtk.py~     Wed Mar  3 09:31:39 2004
+++ backends/backend_gtk.py      Tue Mar  9 12:00:37 2004

@@ -350,47 +351,20 @@
         xox = int(x+ox)
         yoy = int(y+oy)
 
-
-
         imw = min(imw, self.width-xox)
         imh = min(imh, yoy)
-        #print imw, imh, xox, yoy, self.width, self.height
-        image = self.gdkDrawable.get_image(xox, self.height-yoy, imw,
imh)
-        #return
-
-
-        tr = int(rgb[0]*255) # text red
-        tg = int(rgb[1]*255) # text green
-        tb = int(rgb[2]*255) # text blue
-
-        ind =  indices(Xs.shape)
-        numRows, numCols = Xs.shape
-        ind.shape = 2, numRows*numCols
-        Xs.shape = numRows*numCols,
-        visible = nonzero(Xs>0)
-        Xs.shape = numRows,numCols
-        for thisInd in visible:
-            j,i = ind[:,thisInd]
-            if i >= imw: continue
-            if j >= imh: continue
-            pixel = image.get_pixel(i, j)
-            br = (pixel >> 16)  & 0xff  # background red
-            bg = (pixel >> 8 ) & 0xff
-            bb = (pixel >> 0)  & 0xff
-            #print br, bg, bb, Xs[j,i]
-
-            alpha = int((255-Xs[j,i])*255)
-
-            nr = (((br - tr) * alpha) + (tr << 16)) >> 16
-            ng = (((bg - tg) * alpha) + (tg << 16)) >> 16
-            nb = (((bb - tb) * alpha) + (tb << 16)) >> 16
-            newpixel = (nr<<16) + (ng<<8) + (nb)
-            
-            image.put_pixel(i, j, newpixel)
 
-        self.gdkDrawable.draw_image(gc.gdkGC, image, 0, 0,
-                                    xox, self.height-yoy, imw, imh)
+        pb=gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB,
+                          has_alpha=1, bits_per_sample=8, width=imw,
height=imh)
+        pbpix=pb.pixel_array
+        pbpix[:,:,3]=Xs
+        pbpix[:,:,0]=int(rgb[0]*255)
+        pbpix[:,:,1]=int(rgb[1]*255)
+        pbpix[:,:,2]=int(rgb[2]*255)
 
+        pb.render_to_drawable(self.gdkDrawable, gc.gdkGC, 0, 0, xox,
self.height-yoy, imw, imh,
+                              gdk.RGB_DITHER_NONE, 0, 0)
+            
         if 0:
             self.gdkDrawable.draw_rectangle(
                 gc.gdkGC, 0, xox,


-- 
Trevor Blackwell      tl...@an...       (650) 210-9272