2008/12/27
<address@hidden>
Hi Yang.
This patch should be OK for DCT decode filter....
As you can see in the 7.4.8 section of the ISO PDF specification the
DCT decoder uses one parameter:
ColorTransform (integer, optional)
A code specifying the transformation that shall be performed
on the sample values:
0 - no transformation
1 - If the image has three colour components, RGB values shall
be transformed to YUV before encoding and from YUV to RGB
after decoding. If the image has four components, CMYK values
shall be transformed to YUVK before encoding and from YUVK to
CMYK after decoding. This option shall be ignored if the image
has one or two colour components.
If the encoding algorithm has inserted the Adobe-defined
marker code in the encoded data indicating the ColorTransform
value, then the colours shall be transformed, or not, after
the DCT decoding has been performed according to the value
provided in the encoded data and the value of this dictionary
entry shall be ignored. If the Adobe-defined marker code in
the encoded data indicating the ColorTransform value is not
present then the value specified in this dictionary entry will
be used. If the Adobe-defined marker code in the encoded data
indicating the ColorTransform value is not present and this
dictionary entry is not present in the filter dictionary then
the default values of ColorTranform shall be 1 if the image
has three components and 0 otherwise.
Your implementation does not seem to be aware of the parameter.