[cups] Mac OSX with CUPS 1.7.2 Printing fuzzy on Zebra GK420d

Helge Blischke HelgeBlischke at web.de
Tue Jul 8 06:23:30 PDT 2014


Am 08.07.2014 um 13:48 schrieb Matthew Warren:

> Thanks for the reply and advice!
>
> I printed another label and tried to include all the log stuff again https://www.evernote.com/shard/s273/sh/17d4d1ab-d712-4e10-88a9-5465a0bc0aaa/68062e9ddeeaad629c7f0017dd00fba9
>
> Here is one of the original images, it has a DPI of 300, 356x869  
> pixels, RGB, Depth is 9
>
> https://www.dropbox.com/s/2pgmcwj2z3i3pg3/PPI%201st%20Class.jpg
>
> I've had a look at the filter you suggest, but that is going beyond  
> my technical skills to get that working, do you know of any guides  
> (above and beyond the readme) that show how to install filters?
>
>
> On 8 Jul 2014, at 12:23, Helge Blischke <HelgeBlischke at web.de> wrote:
>
>>
>> Am 08.07.2014 um 12:01 schrieb Matthew Warren:
>>
>>> Machine:  Macbook Air
>>> OS: OSX 10.9.3
>>> CUPS: 1.7.2
>>> Driver: ZPL
>>> Printer: Brand new Zebra GK420d
>>>
>>>
>>>
>>> We are trying to print PDF shipping labels, these labels have high  
>>> quality JPG images in them as well as text and a barcode. Here is  
>>> the label https://www.dropbox.com/s/2bygmavx0tw17s2/label%20%2823%29.pdf
>>>
>>> Problem: The quality is very fuzzy/distorted. The JPG images are  
>>> the worst effected but even the barcode and text are not good. See  
>>> photo here https://www.dropbox.com/s/in3g64f8g69sk2d/IMAG0062.jpg
>>>
>>> Here is the error log from CUPS https://www.dropbox.com/s/88ipbc4bmtjsqho/error_log
>>>
>>> Printer works fine on Windows machine.
>>>
>>> We have replicated this problem on multiple Mac machines (our  
>>> customers) with the same setup as above.
>>>
>>> We have printed hundreds of test trying various different  
>>> solutions and we have only had any improvements when we load the  
>>> PDF into Gimp and convert it to 1 bit colour (black/white) with a  
>>> DPI of 203 save it in XCF format, its better but not perfect.  If  
>>> we then save that into PDF format again, it makes it worse again.
>>>
>>> We have tried converting to other formats like SVG/EPS without luck.
>>>
>>> I can live with the text quality but the images and barcode are  
>>> not good enough for the courier.  Problem seems linked to CUPS/ 
>>> Zebra when it converts the PDF to its 1 bit colour and does not do  
>>> a great job, but I am no expert.
>>>
>>> Desperate for some help/advice and I would be extremely grateful  
>>> for any!
>>>
>>>
>>>
>>
>> It's a pity that your error_log snippet lacks the initial messages  
>> of the job in question; so the messages regarding what
>> filters are used is missing. And, could you please tell more  
>> details about the original images (color space, resolution, etc.).
>> My suspicion is that the default image to pdf filter, cgimagetopdf,  
>> and the filter to convert the PDF to cups-raster, cgpdftoraster,
>> both use inappropriate settings with respect to color space(s) and  
>> device resolution.
>>
>> Perhaps you could try the filter from
>> http://sourceforge.net/projects/cupsaddons/files/filter-gstoraster/
>> which has been heavily testede with diverse Zebra printers.
>>
>> Helge
>>

Matthew,

on the short term, I suspect there is nothing you can do really. I  
simulated (with the cupsfilter utility) printing your image
which my gstroraster filter and got essentially the same  
nonsatisfactory result.

A more detailed analysis showed that:
(1) the source image has a resolution of 300 x 300 pixel, and the  
destination resolution of the printer is 203 x 203 pixel.
(2) the source image colorspace is RGB, and the desination color space  
is b/w
(3) the image within the PDF has the attribute "/Interpolate true".
Thus, the source image has to be converted from 300x300 dpi RGB to  
203x203dpi b/w, which almost certainly
(and, in this case, in reality) leads to jaggy edges in the  
destination image.

The best approach, I think, would be to design the source images as b/ 
w images with the destination resolution.

Helge




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