[scribus] CMYK Values Overwritten

Mike Sleger chappa-ai at q.com
Fri Jun 17 00:17:12 UTC 2011

I did further testing, and it turns out that any percentage value not evenly divisible by 20 gets altered.  Values evenly distributed by 20 retain their entered value.  Granted, there probably isn't any perceptible difference between 41.00% and 41.18%, but from an end-user perspective 41.00 should be 41.00, not 41.18.  A user should get the values they specified.


On Jun 16, 2011, at 6:08 PM, Gregory Pittman wrote:

> On 06/16/2011 06:52 PM, Owen wrote:
>> On Wed, 15 Jun 2011 21:45:15 -0600
>> Mike Sleger<chappa-ai at q.com>  wrote:
>>> If I define a CMYK color as 0.00%, 30.00%, 60.00%, 5.00% and save the
>>> change, then go back and review the color, its stored values are
>>> instead 0.00%, 30.20%, 60.00%, 5.10%.  (If I had wanted 30.20 and
>>> 5.10 I would have specified them.)  Similarly, another color defined
>>> as 100.00%, 41.00%, 0.00%, 55.00% is actually remembered or stored as
>>> 100.00%, 41.18%, 0.00%, 54.90%.  Is this normal behavior that people
>>> just accept because it's "within tolerance limits"?  Can't the
>>> program keep track of single-precision floating-point values?  If
>>> color values are changed, what else gets changed?
>> I would suggest that this is a minor bug that should be reported at
>> http://bugs.scribus.net (I cannot find such a report)
> As I look at this a bit and check some things, it may be that there is a problem with the precision of these percentages, decimal values, and the hex values.
> Colors in RGB can be 0 to 255, in hex 00 to ff. When I set a value for a CMYK color in Scribus, then save the file, the color will be saved in hex, which may not have the precision at a level of precisely 30%.
> This is not to say that this is not a bug, but if we consider that your 30% will be converted to hex, then converted back when you check it in the colors dialog again, maybe it isn't surprising it might come out as 30.2%.
> In fact, you can observe the phenomenon in the dialog by making values for CMYK, switching to RGB, then switching back to CMYK.
> My guess is that a value in CMYK of 30% vs 30.2% has little meaning.
> Greg
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