Banding in gradient fills

[Helge Blischke]

David Williams wrote:
>>David Williams wrote:
>>
>>>Hi,
>>>I've set up a colour laser printer using the manufacturer's PPD file and filter 'rastertosamsungsplc'.
>>>On the printer test page and on prints from graphics programs such as Inkscape and Open Office Draw. smooth gradients (colour and grey) are reproduced as steps of  different density. The 'normal' resolution is 600dpi and cannot be changed.
>>>I can't see a way in Cups to change any settings. Do you know of a way I can fix this, please?
>>>
>>>Thanks
>>>Dave.
>>
>>You didn't tell what make and model your printer is. If it is
>>a PostScript level 2 printer (of fed with level 2 PostScript),
>>banding is normal, as smooth gradients are a level 3 feature
>>and need to be emulated in levels <3 by banding. To select
>>the color parameters of the adjacend bands so that banding
>>is nardly recognizable is not trivial and is heavily dependent
>>on the printer's internals (hard- and firmware).
>>
>>Helge
>>
>>--
>>Helge Blischke
>>Softwareentwicklung
>>
>>H.Blischke at acm.org
> 
> 
> Hi,
> Thankyou for the reply. It is a Samsung CLP-510.
> Below is the top part of the PPD file. It prints images very well e.g. web pages, and Inkscape has an option to 'print as bitmap' so I was a bit disappointed with the banding. Do you need any more information than that below.
> Once again, thankyou for looking at the problem.
> John.
> 
> *PPD-Adobe: "4.3"
> *FormatVersion: "4.3"
> *FileVersion: "1.5"
> *LanguageVersion: English
> *LanguageEncoding: ISOLatin1
> *PCFileName:  "CLP510.PPD"
> *Manufacturer: "SAMSUNG"
> *Product: "(ColorLaserPrinter)"
> *cupsVersion: 1.0
> *cupsManualCopies: False
> *cupsModelNumber:  2
> *cupsFilter:  "application/vnd.cups-postscript 0 rastertosamsungsplc"
> *ModelName:     "Samsung CLP-510"
> *ShortNickName: "CLP-510"
> *linuxLanguage: "SPL-C"
> *linuxPriority: "1"
> *linuxURL:    "http://www.samsungprinter.com/"
> *linuxIdentify: "CLP-510"
> *NickName:      "Samsung CLP-510 Series (SPL-C)"
> *PSVersion: "(3010.000) 550"
> *LanguageLevel: "3"
> *ColorDevice: True
> *DefaultColorSpace: Gray
> *FileSystem:  False
> *Throughput:  "24"
> *%LandscapeOrientation: Plus90
> *%VariablePaperSize: False
> *%TTRasterizer: Type42
> 
> *OpenUI *Resolution/Resolution: PickOne
> *DefaultResolution: 600
> *Resolution 600/Normal: "<</HWResolution[600 600]>>setpagedevice"
> *CloseUI: *Resolution

Well, from your PPD snippet it is clear that Ghostscript is involved
using the cups raster device to transform PostScript into a special
pixmap format. Te quality of the output thus depends on the version
of Ghostscript used and how the conversion parameters are set.
To generate a pixmap, banding cannot be avoided in principle;
the broader the stripes created the more visible is the banding.

Sorry, as we have only native PostScript printers at our site,
I cannot give sou mor advice.

Helge


-- 
Helge Blischke
Softwareentwicklung

H.Blischke at acm.org