Unexpected CMYK color conversion after PDF flatten
Posted: 2018-04-17T13:09:12-07:00
I'm trying to work through a rather unexpected issue when using convert to flatten a PDF. I'm using the Ruby library MiniMagick and the relevant portion of my code looks like this:
If I'm not mistaken, this should translate to:
The issue is that my PDF comes out with slightly different colors than when it went in! For example, a light blue will be a teal color. Here's a partial diff output of identify -verbose for the before and after PDFs:
I'm totally confused as to why the colors are changing on flatten. Any ideas?
Code: Select all
img.combine_options do |c|
c.units("PixelsPerInch")
c.density(300)
c.resample(300)
c.flatten
end
Code: Select all
convert -units "PixelsPerInch" -density 300 -resample 300 -flatten myfile.pdf
Code: Select all
23,26c23,26
< mean: 20656.3 (0.315195)
< standard deviation: 18880.7 (0.288101)
< kurtosis: -1.27762
< skewness: 0.240914
---
> mean: 18761.9 (0.286287)
> standard deviation: 18189.6 (0.277556)
> kurtosis: -0.93749
> skewness: 0.437875
30,33c30,33
< mean: 13986.5 (0.21342)
< standard deviation: 18464.2 (0.281746)
< kurtosis: -0.530197
< skewness: 0.969841
---
> mean: 14568.8 (0.222306)
> standard deviation: 19541.1 (0.298178)
> kurtosis: -0.629342
> skewness: 0.963269
37,40c37,40
< mean: 18504.1 (0.282355)
< standard deviation: 20566.7 (0.313828)
< kurtosis: -0.50555
< skewness: 0.868613
---
> mean: 19502.4 (0.297588)
> standard deviation: 20893.4 (0.318814)
> kurtosis: -0.654855
> skewness: 0.756789
43,47c43,47
< max: 57568 (0.878431)
< mean: 8170.54 (0.124674)
< standard deviation: 16077.5 (0.245327)
< kurtosis: 2.19983
< skewness: 1.9042
---
> max: 56797 (0.866667)
> mean: 8710.56 (0.132915)
> standard deviation: 17196.5 (0.262402)
> kurtosis: 1.73386
> skewness: 1.81423
52,56c52,56
< mean: 15329.4 (0.233911)
< standard deviation: 18566.7 (0.283309)
< kurtosis: -0.172968
< skewness: 1.0082
< Total ink density: 299.608%
---
> mean: 15385.9 (0.234774)
> standard deviation: 19006.4 (0.290019)
> kurtosis: -0.199657
> skewness: 1.00662
> Total ink density: 296.078%
77,78c77,78
< date:create: 2018-04-17T14:40:17-05:00
< date:modify: 2018-04-17T14:40:17-05:00
---
> date:create: 2018-04-17T14:40:25-05:00
> date:modify: 2018-04-17T14:40:25-05:00
80,81c80,81
< pdf:Version: PDF-1.4
< signature: 1404ed04acf621bec7ae56c0d0e8c740422b45e8f41b6e79a62461328d34cd59
---
> pdf:Version: PDF-1.3 1 0 obj <<
> signature: e07a3bb439b877b4b4fd76ec4588b248506f559d9a4b7294e9a05551bb35dc83
88,90c88,90
< Pixels per second: 104.3MB
< User time: 0.010u
< Elapsed time: 0:01.010
---
> Pixels per second: 0B
> User time: 0.000u
> Elapsed time: 0:01.000