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Document behavior of -c flag for JPEG-LS #66

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12 changes: 7 additions & 5 deletions README
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Expand Up @@ -142,7 +142,9 @@ that, use the command line option -ls:
$ jpeg -ls -c infile.ppm out.jpg

The "-c" command line switch is necessary to disable the color transformation
as JPEG LS typically encodes in RGB and not YCbCr space.
as JPEG LS typically encodes in RGB and not YCbCr space. This will introduce an
application data marker Adobe 14 to indicate the RGB color space in the output
stream.

Optionally, you may specify the JPEG LS "near" parameter (maximum error) with
the -m command line switch:
Expand Down Expand Up @@ -193,10 +195,10 @@ or, for floating point images:
$ jpeg infile.jpg out.pfm


If you want to decode a JPEG LS image, then you may want to tell the
decoder explicitly to disable the color transformation even though the
corresponding marker signalling coding in RGB space is typically missing
for JPEG LS:
If you want to decode a JPEG LS image, even one containing a SPIFF header with
rgb colorspace, then you may want to tell the decoder explicitly to disable the
color transformation even though the corresponding marker signalling coding in
RGB space is typically missing for JPEG LS:

$ jpeg -c infile.jpg out.ppm

Expand Down