def decode(self, dst=None, pixfmt=TJPF_RGB):
bpp = jpeg.tjPixelSize[pixfmt]
if dst is None:
if self.width is None:
self.parse_header()
sh = [self.height, self.width]
if bpp > 1:
sh.append(bpp)
dst = numpy.zeros(sh, dtype=numpy.uint8)
elif not hasattr(dst, "__array_interface__"):
raise ValueError("dst should be numpy array or None")
if len(dst.shape) < 2:
raise ValueError("dst shape length should 2 or 3")
if dst.nbytes < dst.shape[1] * dst.shape[0] * bpp:
raise ValueError(
"dst is too small to hold the requested pixel format")
self._get_decompressor()
n = self.lib_.tjDecompress2(
self.decompressor.handle_,
ffi.cast("unsigned char*",
self.source.__array_interface__["data"][0]),
self.source.nbytes,
ffi.cast("unsigned char*", dst.__array_interface__["data"][0]),
dst.shape[1], dst.strides[0], dst.shape[0], pixfmt, 0)
if n:
raise JPEGRuntimeError("tjDecompress2() failed with error "
"%d and error string %s" %
(n, self.get_last_error()), n)
return dst
def parse_header(self):
"""Parses JPEG header.
Fills self.width, self.height, self.subsampling.
"""
self._get_decompressor()
whs = ffi.new("int[]", 3)
whs_base = int(ffi.cast("size_t", whs))
whs_itemsize = int(ffi.sizeof("int"))
n = self.lib_.tjDecompressHeader2(
self.decompressor.handle_,
ffi.cast("unsigned char*",
self.source.__array_interface__["data"][0]),
self.source.nbytes,
ffi.cast("int*", whs_base),
ffi.cast("int*", whs_base + whs_itemsize),
ffi.cast("int*", whs_base + whs_itemsize + whs_itemsize))
if n:
raise JPEGRuntimeError("tjDecompressHeader2() failed with error "
"%d and error string %s" %
(n, self.get_last_error()), n)
self.width = int(whs[0])
self.height = int(whs[1])
self.subsampling = int(whs[2])