Converting 100% Black CMYK PDF to TIFF

[andyg2]

I'm trying to convert a 100% black CMYK PDF to TIFF but the resulting TIFF file is not true 100% black.

convert -colorspace CMYK "(0.0%, 0.0%, 0.0%, 100.0%)" -density 600 +antialias 100 in.pdf out.tif
identify out.tif

Channel statistics for tif file:
Cyan:
min: 0 (0)
max: 47288 (0.721569)
mean: 15063.9 (0.22986)
standard deviation: 22032.3 (0.336191)
kurtosis: -1.39336
skewness: 0.778868
Magenta:
min: 0 (0)
max: 44204 (0.67451)
mean: 14081.5 (0.214869)
standard deviation: 20595.4 (0.314265)
kurtosis: -1.39336
skewness: 0.778868
Yellow:
min: 0 (0)
max: 43947 (0.670588)
mean: 15488.3 (0.236337)
standard deviation: 19462.7 (0.296981)
kurtosis: -1.39342
skewness: 0.777192
Black:
min: 0 (0)
max: 57825 (0.882353)
mean: 18420.5 (0.281079)
standard deviation: 26941.6 (0.411103)
kurtosis: -1.39336
skewness: 0.778868
Image statistics:
Overall:
min: 0 (0)
max: 57825 (0.882353)
mean: 12610.8 (0.192429)
standard deviation: 21087.8 (0.32178)
kurtosis: -0.469916
skewness: 1.18775
Total ink density: 295%

Any help on this would be very much appreciated

[fmw42]

convert -colorspace CMYK "(0.0%, 0.0%, 0.0%, 100.0%)" -density 600 +antialias 100 in.pdf out.tif

I don't understand your syntax.

"(0.0%, 0.0%, 0.0%, 100.0%)" is not meaningful in this context nor is it correct IM color definition syntax, nor is it pure black. Also +antialias is probably not meaningful here either. It is used when drawing text to an image.

For color definitions, see http://www.imagemagick.org/script/color.php

If your in.pdf is already cmyk and totally black, why do you need -colorspace cmyk?

What is your in.pdf? Is it cmyk or rgb? Please clarify what you are trying to do and your input image characteristics.


You are probably better converting to RGB before going to tiff

convert -colorspace rgb -density 600 in.pdf out.tiff



Here is a test example:

convert -size 100x100 xc:black -colorspace cmyk test_cmyk.pdf

identify -verbose test_cmyk.pdf
Image: test_cmyk.pdf
Format: PDF (Portable Document Format)
Class: DirectClass
Geometry: 100x100+0+0
Resolution: 72x72
Print size: 1.38889x1.38889
Units: Undefined
Type: ColorSeparation
Base type: ColorSeparation
Endianess: Undefined
Colorspace: CMYK
Depth: 16/1-bit
Channel depth:
cyan: 1-bit
magenta: 1-bit
yellow: 1-bit
black: 1-bit
Channel statistics:
Cyan:
min: 65535 (1)
max: 65535 (1)
mean: 65535 (1)
standard deviation: -0 (-0)
kurtosis: 0
skewness: 0
Magenta:
min: 65535 (1)
max: 65535 (1)
mean: 65535 (1)
standard deviation: -0 (-0)
kurtosis: 0
skewness: 0
Yellow:
min: 65535 (1)
max: 65535 (1)
mean: 65535 (1)
standard deviation: -0 (-0)
kurtosis: 0
skewness: 0
Black:
min: 0 (0)
max: 0 (0)
mean: 0 (0)
standard deviation: -0 (-0)
kurtosis: 0
skewness: 0


convert test_cmyk.pdf test_cmyk.tif

identify -verbose test_cmyk.tif
Image: test_cmyk.tif
Format: TIFF (Tagged Image File Format)
Class: DirectClass
Geometry: 100x100+0+0
Resolution: 72x72
Print size: 1.38889x1.38889
Units: Undefined
Type: ColorSeparation
Base type: ColorSeparation
Endianess: MSB
Colorspace: CMYK
Depth: 16/1-bit
Channel depth:
cyan: 1-bit
magenta: 1-bit
yellow: 1-bit
black: 1-bit
Channel statistics:
Cyan:
min: 65535 (1)
max: 65535 (1)
mean: 65535 (1)
standard deviation: -0 (-0)
kurtosis: 0
skewness: 0
Magenta:
min: 65535 (1)
max: 65535 (1)
mean: 65535 (1)
standard deviation: -0 (-0)
kurtosis: 0
skewness: 0
Yellow:
min: 65535 (1)
max: 65535 (1)
mean: 65535 (1)
standard deviation: -0 (-0)
kurtosis: 0
skewness: 0
Black:
min: 0 (0)
max: 0 (0)
mean: 0 (0)
standard deviation: -0 (-0)
kurtosis: 0
skewness: 0

Now convert this to rgb:


convert test_cmyk.tif -colorspace rgb test_rgb.tif

identify -verbose test_rgb.tif

Image: test_rgb.tif
Format: TIFF (Tagged Image File Format)
Class: DirectClass
Geometry: 100x100+0+0
Resolution: 72x72
Print size: 1.38889x1.38889
Units: Undefined
Type: Bilevel
Base type: Bilevel
Endianess: MSB
Colorspace: RGB
Depth: 1-bit
Channel depth:
gray: 1-bit
Channel statistics:
Gray:
min: 0 (0)
max: 0 (0)
mean: 0 (0)


Which is totally black.