Implement ImageSurface.get_data(), using some code from Paul Colomiets.

bug #44935.

1 files changed, 76 insertions, 37 deletions

diff --git a/test/isurface_get_data.py b/test/isurface_get_data.py
index f2662d4..6875042 100755
--- a/test/isurface_get_data.py
+++ b/test/isurface_get_data.py
@@ -5,46 +5,85 @@ Test ImageSurface.get_data()
 import tempfile
 
 import cairo
-import numpy
 
 if not (cairo.HAS_IMAGE_SURFACE and cairo.HAS_PNG_FUNCTIONS):
   raise SystemExit ('cairo was not compiled with ImageSurface and PNG support')
 
 w, h = 128, 128
 
-surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, w, h)
-ctx = cairo.Context(surface)
-
-ctx.set_source_rgb(1, 1, 1)  # white
-ctx.set_operator(cairo.OPERATOR_SOURCE)
-ctx.paint()
-
-# Draw out the triangle using absolute coordinates
-ctx.move_to(w/2, h/3)
-ctx.line_to(2*w/3, 2*h/3)
-ctx.rel_line_to(-1*w/3, 0)
-ctx.close_path()
-
-ctx.set_source_rgb(0, 0, 0)  # black
-ctx.set_line_width(15)
-ctx.stroke()
-_, outFileName = tempfile.mkstemp(prefix='pycairo_', suffix='.png')
-surface.write_to_png(outFileName)
-print "see %s output file" % outFileName
-
-# modify surface using numpy
-buf = surface.get_data()
-# alternative which should work (?) but reports
-# TypeError: buffer is read-only
-# - is a Python bug?
-#buf = buffer (surface1)
-
-a = numpy.ndarray(shape=(w,h,4), dtype=numpy.uint8, buffer=buf)
-
-# draw a vertical line
-a[:,40,0] = 255  # byte 0 is blue on little-endian systems
-a[:,40,1] = 0
-a[:,40,2] = 0
-_, outFileName = tempfile.mkstemp(prefix='pycairo_', suffix='.png')
-surface.write_to_png(outFileName)
-print "see %s output file" % outFileName
+def create_surface():
+  "create black triangle on white background"
+  surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, w, h)
+  ctx = cairo.Context(surface)
+
+  ctx.set_source_rgb(1, 1, 1)  # white
+  ctx.set_operator(cairo.OPERATOR_SOURCE)
+  ctx.paint()
+
+  # Draw out the triangle using absolute coordinates
+  ctx.move_to(w/2, h/3)
+  ctx.line_to(2*w/3, 2*h/3)
+  ctx.rel_line_to(-1*w/3, 0)
+  ctx.close_path()
+
+  ctx.set_source_rgb(0, 0, 0)  # black
+  ctx.set_line_width(15)
+  ctx.stroke()
+  return surface
+
+
+def test_python_buffer():
+  "get_data() and modify data using Python"
+  surface = create_surface()
+  _, f1 = tempfile.mkstemp(prefix='pycairo_', suffix='.png')
+  surface.write_to_png(f1)
+
+  buf = surface.get_data()
+  stride = surface.get_stride()
+  for i in range(h):
+      offset = i * stride + 120
+      buf[offset]     = b'\xFF'
+      buf[offset + 1] = b'\x00'
+      buf[offset + 2] = b'\x00'
+
+  _, f2 = tempfile.mkstemp(prefix='pycairo_', suffix='.png')
+  surface.write_to_png(f2)
+  print("""\
+test_python_buffer:
+  original data: %s
+  modified data: %s
+""" % (f1, f2))
+
+
+def test_numpy_and_python_buffer():
+  "get_data() and modify data using numpy"
+  try:
+    import numpy
+  except:
+    print("numpy not installed")
+    return
+
+  surface = create_surface()
+  _, f1 = tempfile.mkstemp(prefix='pycairo_', suffix='.png')
+  surface.write_to_png(f1)
+
+  buf = surface.get_data()
+
+  a = numpy.ndarray(shape=(w,h,4), dtype=numpy.uint8, buffer=buf)
+
+  # draw a vertical line
+  a[:,40,0] = 255  # byte 0 is blue on little-endian systems
+  a[:,40,1] = 0
+  a[:,40,2] = 0
+
+  _, f2 = tempfile.mkstemp(prefix='pycairo_', suffix='.png')
+  surface.write_to_png(f2)
+  print("""\
+test_numpy_and_python_buffer:
+  original data: %s
+  modified data: %s
+""" % (f1, f2))
+
+
+test_python_buffer()
+test_numpy_and_python_buffer()