python does auto complx/uncomplx

this is a bit ugly :-(

TODO

@@ -1,29 +1,9 @@
-- we need to be able to run .polar() on xyz images ... argh
-
-   - could special-case vips_complex() to work for multi-band int images as
-     well as complex
-
-     would need to output as multi-band float
-
-     what about other cases though? cast real to complex?
-
-   - could add new ops for polar/rect of real images with two bands
-
-   - could add a thing to Vips.py to do this
-
-   - could add full support for complex arithmetic ... linear would need an
-     extra arg for complex constants
-
-   - could abandon complex images and just use 2*bands instead, have complex
-     as a flag you set? or just rely on FOURIER
-
-  paste fixed up run_cmplx() into Vips.py
 
 - easy to get a segv with Nicolas's interpolators, argh
 
   just with float images?
 
-  try to_polar, set LBB, zoom in and scroll around a bit
+  try to_polar workspace, set LBB, zoom in and scroll around a bit
 
 
 

python/Vips.py

@@ -134,6 +134,40 @@ def arrayize(gtype, value):
 
     return value
 
+def run_cmplx(fn, image):
+    """Run a complex function on a non-complex image.
+
+    The image needs to be complex, or have an even number of bands. The input
+    can be int, the output is always float or double.
+    """
+    original_format = image.format
+
+    if not Vips.band_format_iscomplex(image.format):
+        if image.bands % 2 != 0:
+            raise "not an even number of bands"
+
+        if not Vips.band_format_isfloat(image.format):
+            image = image.cast(Vips.BandFormat.FLOAT)
+
+        if image.format == Vips.BandFormat.DOUBLE:
+            new_format = Vips.BandFormat.DPCOMPLEX
+        else:
+            new_format = Vips.BandFormat.COMPLEX
+
+        image = image.copy(format = new_format, bands = image.bands / 2)
+
+    image = fn(image)
+
+    if not Vips.band_format_iscomplex(original_format):
+        if image.format == Vips.BandFormat.DPCOMPLEX:
+            new_format = Vips.BandFormat.DOUBLE
+        else:
+            new_format = Vips.BandFormat.FLOAT
+
+        image = image.copy(format = new_format, bands = image.bands * 2)
+
+    return image
+
 class Error(Exception):
     """An error from vips.
 
@@ -911,11 +945,11 @@ class Image(Vips.Image):
 
     def polar(self):
         """Return an image converted to polar coordinates."""
-        return self.complex(Vips.OperationComplex.POLAR)
+        return run_cmplx(lambda x: x.complex(Vips.OperationComplex.POLAR), self)
 
     def rect(self):
         """Return an image converted to rectangular coordinates."""
-        return self.complex(Vips.OperationComplex.RECT)
+        return run_cmplx(lambda x: x.complex(Vips.OperationComplex.RECT), self)
 
     def conj(self):
         """Return the complex conjugate of an image."""

python/example/cod.py

@@ -11,37 +11,6 @@ from gi.repository import Vips
 
 #Vips.cache_set_trace(True)
 
-# Run a function expecting a complex image on an image with an even number of
-# bands
-def run_cmplx(fn, image):
-    original_format = image.format
-
-    if not Vips.band_format_iscomplex(image.format):
-        if image.bands % 2 != 0:
-            raise "not an even number of bands"
-
-        if not Vips.band_format_isfloat(image.format):
-            image = image.cast(Vips.BandFormat.FLOAT)
-
-        if image.format == Vips.BandFormat.DOUBLE:
-            new_format = Vips.BandFormat.DPCOMPLEX
-        else:
-            new_format = Vips.BandFormat.COMPLEX
-
-        image = image.copy(format = new_format, bands = image.bands / 2)
-
-    image = fn(image)
-
-    if not Vips.band_format_iscomplex(original_format):
-        if image.format == Vips.BandFormat.DPCOMPLEX:
-            new_format = Vips.BandFormat.DOUBLE
-        else:
-            new_format = Vips.BandFormat.FLOAT
-
-        image = image.copy(format = new_format, bands = image.bands * 2)
-
-    return image
-
 def to_polar(image):
     """Transform image coordinates to polar.
 
@@ -55,8 +24,9 @@ def to_polar(image):
     scale = min(image.width, image.height) / float(image.width)
     xy *= 2.0 / scale
 
-    # to polar, scale vertical axis to 360 degrees
-    index = run_cmplx(lambda x: x.polar(), xy)
+    index = xy.polar()
+
+    # scale vertical axis to 360 degrees
     index *= [1, image.height / 360.0]
 
     return image.mapim(index)
@@ -72,8 +42,9 @@ def to_rectangular(image):
     xy = Vips.Image.xyz(image.width, image.height)
     xy *= [1, 360.0 / image.height]
 
-    # to rect, scale to image rect
-    index = run_cmplx(lambda x: x.rect(), xy)
+    index = xy.rect()
+
+    # scale to image rect
     scale = min(image.width, image.height) / float(image.width)
     index *= scale / 2.0
     index += [image.width / 2.0, image.height / 2.0]