I've done some testing in the meanwhile, trying to perform this
operation by the use of 16-bit images. After downloading and installing
the current Windows 16-bit executable (6.3.5-10 Q16), I stripped the
operation down to:
convert -depth 16 -size 64x64 xc:grey50 grey.tif
identify -verbose grey.tif >log.txt
convert grey.tif -fx "1/256" x.tif
identify -verbose x.tif >>log.txt
convert x.tif x.tif -compose multiply -composite x2.tif
identify -verbose x2.tif >>log.txt
and got strange results (see below).
Anyone who can throw some light onto this?
Wolfgang Hugemann
========
Logfile (abbreviated):
Image: grey.tif
Format: TIFF (Tagged Image File Format)
Class: DirectClass
Geometry: 64x64+0+0
Type: Grayscale
Endianess: MSB
Colorspace: Gray
Depth: 9-bit
Channel depth:
Gray: 9-bit
Channel statistics:
Gray:
Min: 256 (0.500008)
Max: 256 (0.500008)
Mean: 256 (0.500008)
Standard deviation: 0 (0)
Histogram:
4096: (32768,32768,32768) #800080008000 grey50
...
Tiff:document: grey.tif
Tiff:rows-per-strip: 64
Tiff:software: ImageMagick 6.3.5 09/18/07 Q16
...
Image: x.tif
Format: TIFF (Tagged Image File Format)
Class: DirectClass
Geometry: 64x64+0+0
Type: Grayscale
Endianess: MSB
Colorspace: Gray
Depth: 9-bit
Channel depth:
Gray: 9-bit
Channel statistics:
Gray:
Min: 2 (0.00390631)
Max: 2 (0.00390631)
Mean: 2 (0.00390631)
Standard deviation: 0 (0)
Histogram:
4096: ( 256, 256, 256) #010001000100
rgb(0.390631%,0.390631%,0.390631%)
...
Image: x2.tif
Format: TIFF (Tagged Image File Format)
Class: DirectClass
Geometry: 64x64+0+0
Type: Grayscale
Endianess: MSB
Colorspace: Gray
Depth: 16-bit
Channel depth:
Gray: 16-bit
Channel statistics:
Gray:
Min: 1 (1.5259e-005)
Max: 1 (1.5259e-005)
Mean: 1 (1.5259e-005)
Standard deviation: 0 (0)
Histogram:
4096: ( 1, 1, 1) #000100010001
rgb(0.0015259%,0.0015259%,0.0015259%)
...
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