Remove sBIT shifting in asDirect
GitOrigin-RevId: 14faaffc334b7e12c0a66bb036895e5ea56fa38b
Change-Id: Ia78e3b66cfdae9febd92e93e20984fa8b40ef403
diff --git a/code/png.py b/code/png.py
index 11b19b5..d7245c7 100755
--- a/code/png.py
+++ b/code/png.py
@@ -1881,16 +1881,8 @@
(*width*, *height*, *rows*, *info*)
- This method normally returns pixel values with
- the bit depth they have in the source image, but
- when the source PNG has an ``sBIT`` chunk it is inspected and
- can reduce the bit depth of the result pixels;
- pixel values will be reduced according to the bit depth
- specified in the ``sBIT`` chunk.
- PNG nerds should note a single result bit depth is
- used for all channels:
- the maximum of the ones specified in the ``sBIT`` chunk.
- An RGB565 image will be rescaled to 6-bit RGB666.
+ This method returns pixel values with
+ the bit depth they have in the source image.
The *info* dictionary that is returned reflects
the `direct` format and not the original source image.
@@ -1922,11 +1914,11 @@
info["alpha"] = bool(self.trns)
info["bitdepth"] = 8
info["planes"] = 3 + bool(self.trns)
- plte = self.palette()
+ palette = self.palette()
def iterpal(pixels):
for row in pixels:
- row = [plte[x] for x in row]
+ row = [palette[x] for x in row]
yield array("B", itertools.chain(*row))
pixels = iterpal(pixels)
@@ -1961,23 +1953,7 @@
)
pixels = itertrns(pixels)
- targetbitdepth = None
- if self.sbit:
- sbit = struct.unpack("%dB" % len(self.sbit), self.sbit)
- targetbitdepth = max(sbit)
- if targetbitdepth > info["bitdepth"]:
- raise Error("sBIT chunk %r exceeds bitdepth %d" % (sbit, self.bitdepth))
- if min(sbit) <= 0:
- raise Error("sBIT chunk %r has a 0-entry" % sbit)
- if targetbitdepth:
- shift = info["bitdepth"] - targetbitdepth
- info["bitdepth"] = targetbitdepth
- def itershift(pixels):
- for row in pixels:
- yield [p >> shift for p in row]
-
- pixels = itershift(pixels)
return x, y, pixels, info
def asRGB(self):
diff --git a/code/test_png.py b/code/test_png.py
index 06b7de3..81fe5cd 100644
--- a/code/test_png.py
+++ b/code/test_png.py
@@ -105,10 +105,12 @@
source_pixels = bytearray(mask & x for x in range(1, 256))
w.write_array(f, source_pixels)
r = png.Reader(bytes=f.getvalue())
- x, y, pixels, meta = r.asDirect()
+ x, y, pixels, info = r.asDirect()
self.assertEqual(x, 15)
self.assertEqual(y, 17)
- self.assertEqual(list(itertools.chain(*pixels)), list(source_pixels))
+ rbitdepth = info["bitdepth"]
+ shift = rbitdepth - n
+ self.assertEqual([v >> shift for v in itertools.chain(*pixels)], list(source_pixels))
def test_L2(self):
"""Test L2."""
