High Level Output Devices

Table of contents

For other information, see the Ghostscript overview.


Overview

High level devices are Ghostscript output devices which do not render to a raster, in general they produce 'vector' as opposed to bitmap output. Such devices currently include; pdfwrite, ps2write, eps2write, txtwrite, xpswrite, pxlmono and pxlcolor.

Although these devices produce output which is not a raster, they still work in the same general fashion as all Ghostscript devices. The input (PostScript, PDF, XPS, PCL or PXL) is handled by an appropriate interpreter, the intepreter processes the input and produces from it a sequence of drawing 'primitives' whcih are handed to the device. The device decides whether to handle the primitive itself, or call upon the graphics library to render the primitive to the final raster.

Primitives are quite low level graphics operations; as an example consider the PDF sequence '0 0 100 100 re f'. This contrstructs a rectangle with the bottom left corner at 0,0 whcih is 100 units wide by 100 units high, and fills it with the current color. A lower level implementation using only primitives would first move the current point to 0,0, then construct a line to 0,100, then a line to 100,100, a line to 100, 0 and finally a line back to 0,0. It would then fill the result.

Obviously that's a simple example but it serves to demonstrate the point.

Now the raster devices all call the graphcs library to process primitives (though they may choose to take some action first) and render the result to a bitmap. The high level devices instead reassemble the primitives back into high level page description and write the result to a file. This means that the output, while it should be visually the same as the input (because it makes the same marks), is not the same as the original input, even if the output Page Description Language is the same as the input one was (eg PDF to PDF).

Why is ths important ? Firstly because the description of the page won't be the same, if your worflow relies upon (for example) finding rectangles in the description then it might not work after it has been processed by a high level device, as the rectangles may all have turned into lengthy path descriptions.

In addition, any part of the original input which does not actually make marks on the page (such as hyperlinks, bookmarks, comments etc) will normally not be present in the output, even if the output is the same format. In general the PDF interpreter and the PDF output device (pdfwrite) try to preserve the non-marking information from the input, but some kinds of content are not carrried across, in particular comments are not preserved.

We often hear from users thet they are 'splitting' PDF files, or 'modifying' them, or converting them to PDF/A, and its important to realise that this is not what's happening. Instead a new PDF file is being created, which should look the same as the original, but the actual insides of the PDF file are not the same as the original. Ths may not be a problem, but if its important to keep the original contents, then you need to use a different tool (we'd suggest MuPDF, also available from Artifex). Of course, if the intention is to produce a modified PDF file (for example, reducing the resolution of images, or changing the colour space), then clearly you cannot keep the original contents unchanged, and pdfwrite performs these tasks well.


PCL-XL (PXL)

The pxlmono and pxlcolor devices output HP PCL-XL, a graphic language understood by many recent laser printers.

Options

-dCompressMode=1 | 2 | 3 (default is 1)
Set the compression algorithm used for bitmap graphics. RLE=1, JPEG=2, DeltaRow=3. When JPEG=2 is on, it is applied only to full-color images; indexed-color graphics and masks continues to be compressed with RLE.

Text output

The txtwrite device will output the text contained in the original document as Unicode.

Options

-dTextFormat=0 | 1 | 2 | 3 (default is 3)

Format 0 is intended for use by developers and outputs XML-escaped Unicode along with information regarding the format of the text (position, font name, point size, etc). The XML output is the same format as the MuPDF output, but no additional processing is performed on the content, so no block detection.

Format 1 uses the same XML output format, but attempts similar processing to MuPDF, and will output blocks of text. Note the alogrithm used is not the same as the MuPDF code, and so the results will not be identical.

Format 2 outputs Unicode (UCS2) text (with a Byte Order Mark) which approximates the layout of the text in the original document.

Format 3 is the same as format 2, but the text is encoded in UTF-8.


XPS file output

The xpswrite device writes its output according to the Microsoft XML Paper Specification. This specification was later amended to the Open XML Paper specification, submitted to ECMA International and adopted as ECMA-388.

This device currently has no special configuration parameters.


The family of PDF and PostScript output devices


Common controls and features

The PDF and PostScript (including Encapsulated PostScript, or EPS) devices have much of their code in common, and so many of the controlling parameters are also common amongst the devices. The pdfwrite, ps2write and eps2write devices createPDF or PostScript files whose visual appearance should match, as closely as possible, the appearance of the original input (PS, PDF, XPS, PCL, PXL). There are a number of caveats as mentioned in the overview above. In adition the general comments there are some additional points that bear mentioning;

PCL has a graphcs model which differs significantly from the PostScript or PDF one, in particular it has a form of transparency called RasterOps, some aspects of which cannot be represented in PDF at a high level (or at all, in PostScript). The pdfwrite device makes no attempt to handle thse, and the resulting PDF file will not match the original input. The only way to deal with these types of file is to render the whole page to a bitmap and then 'wrap' the bitmap as a PDF file. Currently we do not do this either, but it is possible that a future enhancement may do so.

If the input contains PDF-compatible transparency, but the ps2weite device is selected, or the pdfwrite device is selected, but has been told to limit the PDF feature set to a version less than 1.4, the transparency cannot be preserved. In this case the entire page is rendered to a bitmap and that bitmap is 'wrapped up' in appropriate PDF or PostScript content. The output should be visually the same as the input, but since it has been rendered it will not scale up or down well, unlike the original, vector, content of the input.

The options in the command line may include any switches that may be used with the language interpreter appropriate for the input (see here for a complete list). In addition the following options are common to all the pdfwrite family of devices, and should work when specified on the comand line with any of the language interpreters.

-rresolution
Sets the resolution for pattern fills, for fonts that must be converted to bitmaps and any other rendering required (eg rendering transparent pages for output to PDF versions < 14). The default internal resolution for pdfwrite is 720dpi.
-dUNROLLFORMS
When converting from PostScript, pdfwrite (and ps2write) preserve the use of Form resources as Form XObjects in the output. Some badly written PostScript can cause this to produce incorrect output (the Quality Logic CET tests for example). By setting this flag, forms will be unrolled and stored in the output each time they are used, which avoids the problems. Note that the output file will of course be larger this way. We do not attempt to preserve Form XObjects from PDF files, unless they are associaed with transparency groups.
-dNoOutputFonts
Ordinarily the pdfwrite device family goes to considerable lengths to preserve fonts from the input as fonts in the output. However in some highly specific cases it can be useful to have the text emitted as linework/bitmaps instead. Setting this switch will prevent these devices from emitting any fonts, all text will be stored as vectors (or bitmaps in the case of bitmapped fonts) in the page content stream. Note that this will produce larger output which will process more slowly, render differently and particularly at lower resolution produce less consistent text rendering. Use with caution.
-dCompressFonts=boolean
Defines whether pdfwrite will compress embedded fonts in the output. The default value is true; the false setting is intended only for debugging as it will result in larger output.
-dCompressStreams=boolean
Defines whether pdfwrite will compress streams other than those in fonts or pages in the output. The default value is true; the false setting is intended only for debugging as it will result in larger output.

Distiller Parameters

Options may also include -dparameter=value or -sparameter=string switches for setting "distiller parameters", Adobe's documented parameters for controlling the conversion of PostScript into PDFprocess. The PostScript setdistillerparams and currentdistillerparams operators are also recognized when the input is PostScriptps2pdf, and provide an equivalent way to set these parameters from within a PostScript input file.

Although the name implies that these parameters are for controlling PDF output, in fact the whole family of devices use these same parameters to control the conversion into PostScript and EPS as well.

The pdfwrite family of devices recognize all of the Acrobat Distiller 5 parameters defined in the DistillerParameters (version 5) document available from the Adobe web site. Cells in the table below containing '=' mean that the value of the parameter is the same as in the "default" column.

Parameter name      Notes    default    screen    ebook    printer    prepress

AlwaysEmbed(13)[ ]====
AntiAliasColorImages(0)false====
AntiAliasGrayImages(0)false====
AntiAliasMonoImages(0)false====
ASCII85EncodePagesfalse====
AutoFilterColorImages(1)true====
AutoFilterGrayImages(1)true====
AutoPositionEPSFiles(0)true====
AutoRotatePages/PageByPage/PageByPage/All/None/None
Binding(0)/Left====
CalCMYKProfile(0)()====
CalGrayProfile(0)()====
CalRGBProfile(0)()====
CannotEmbedFontPolicy(0)/Warning/Warning/Warning/Warning/Error
ColorACSImageDict(13)(note 7)(note 10)(note 10)(note 8)(note 9)
ColorConversionStrategy(0,6)LeaveColorUnchangedRGBRGBUseDeviceIndependentColorLeaveColorUnchanged
ColorImageDepth-1====
ColorImageDict(13)(note 7)====
ColorImageFilter/DCTEncode====
ColorImageDownsampleThreshold1.5====
ColorImageDownsampleType(3)/Subsample/Average/Average/Average/Bicubic
ColorImageResolution7272150300300
CompatibilityLevel1.41.31.41.41.4
CompressPages(14)true====
ConvertCMYKImagesToRGBfalse====
ConvertImagesToIndexed(0)false====
CoreDistVersion4000====
CreateJobTicket(0)falsefalsefalsetruetrue
DefaultRenderingIntent/Default====
DetectBlends(0)true====
DoThumbnails(0)falsefalsefalsefalsetrue
DownsampleColorImagesfalsetruetruefalsefalse
DownsampleGrayImagesfalsetruetruefalsefalse
DownsampleMonoImagesfalsetruetruefalsefalse
EmbedAllFontstruefalsetruetruetrue
EmitDSCWarnings(0)false====
EncodeColorImagestrue====
EncodeGrayImagestrue====
EncodeMonoImagestrue====
EndPage(0)-1====
GrayACSImageDict(13)(note 7)(note 7)(note 10)(note 8)(note 9)
GrayImageDepth-1====
GrayImageDict(13)(note 7)====
GrayImageDownsampleThreshold1.5====
GrayImageDownsampleType(3)/Subsample/Average/Bicubic/Bicubic/Bicubic
GrayImageFilter/DCTEncode====
GrayImageResolution7272150300300
ImageMemory(0)524288====
LockDistillerParamsfalse====
LZWEncodePages(2)false====
MaxSubsetPct100====
MonoImageDepth-1====
MonoImageDict(13)<<K -1>>====
MonoImageDownsampleThreshold1.5====
MonoImageDownsampleType/Subsample/Subsample/Subsample/Subsample/Bicubic
MonoImageFilter/CCITTFaxEncode====
MonoImageResolution30030030012001200
NeverEmbed(13)(note 11)(note 12)(note 11)(note 12)(note 11)(note 12)[ ](note 12)[ ](note 12)
OffOptimizations0====
OPM1====
Optimize(0,5)falsetruetruetruetrue
ParseDSCCommentstrue====
ParseDSCCommentsForDocInfotrue====
PreserveCopyPage(0)true====
PreserveEPSInfo(0)true====
PreserveHalftoneInfofalse====
PreserveOPIComments(0)falsefalsefalsetruetrue
PreserveOverprintSettingsfalsefalsefalsetruetrue
sRGBProfile(0)()====
StartPage(0)1====
SubsetFontstrue====
TransferFunctionInfo(4)/Preserve====
UCRandBGInfo/Remove/Remove/Remove/Preserve/Preserve
UseFlateCompression(2)true====
UsePrologue(0)false====

(note 0) This parameter can be set and queried, but currently has no effect.

(note 1) -dAutoFilterxxxImages=false works since Ghostscript version 7.30. Older versions of Ghostscript don't examine the image to decide between JPEG and LZW or Flate compression: they always use Flate compression.

(note 2) Because of Unisys's threats regarding the Welch patent, ps2pdf does not actually use LZW compression: instead, it treats all requests for LZW compression as calling for Flate compression. Concomitantly, UseFlateCompression is treated as always on, and the value of this parameter is ignored as with note 0. Now that the patent has expired, we could change this should it become worthwhile.

(note 3) The xxxDownsampleType parameters can also have the value /Bicubic (a Distiller 4 feature), ths will use a Mitchell filter. (older versions of pdfwrite simpy used Average instead). Note; if a non-integer downsample factor is used the code will clamp to the nearest integer (if the difference is less than 0.1) or will silently switch to the old bicubic filter, NOT the Mitchell filter.

(note 4) Currently, the transfer function is always applied. If the corresponding parameter is set to /Preserve, the function setting is also copied into the PDF file.

(note 6) Ghostscript specifics : The value UseDeviceIndependentColor requires the device parameter UseCIEColor to be set to true. The value UseDeviceIndependentColorForImages works same as UseDeviceIndependentColor. The value CMYK works with any CompatibilityLevel and requires the device parameter ProcessColorModel to be set to DeviceCMYK. The value sRGB requires the device parameter ProcessColorModel to be set to DeviceRGB, and actually converts to RGB with the default Ghostscript conversion. The new Ghostscript-specific value Gray requires the device parameter ProcessColorModel to be set to DeviceGray, and converts all colors to DeviceGray. The old Ghostscript-specific value UseDeviceDependentColor is now depricated. It is automaticly replaced with sRGB, CMYK, or Gray. With the new color conversion code active it is no longer neccesary to set ProcessColorModel when selecting Gray, RGB or CMYK. It is also no longer neccesary to set UseCIEColor for UseDeviceIndependentColor to work properly, and the use of UseCIEColor is now strongly discouraged. sRGB is not supported, use RGB instead.

(note 7) The default image parameter dictionary is

<< /QFactor 0.9 /Blend 1 /HSamples [2 1 1 2] /VSamples [2 1 1 2] >>

(note 8) The printer ACS image parameter dictionary is

<< /QFactor 0.4 /Blend 1 /ColorTransform 1 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >>

(note 9) The prepress ACS image parameter dictionary is

<< /QFactor 0.15 /Blend 1 /ColorTransform 1 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >>

(note 10) The screen and ebook ACS image parameter dictionary is

<< /QFactor 0.76 /Blend 1 /ColorTransform 1 /HSamples [2 1 1 2] /VSamples [2 1 1 2] >>

(note 11) The default, screen, and ebook settings never embed the 14 standard fonts (Courier, Helvetica, and Times families, Symbol, and ZapfDingbats). This behavior is intentional but can be overrided by:

<< /NeverEmbed [ ] >> setdistillerparams

(note 12) NeverEmbed can include CID font names. If a CID font is substituted in lib/cidfmap, the substitute font name is used when the CID font is embedded, and the original CID font name is used when it is not embedded. NeverEmbed should always specify the original CID font name.

(note 13) The arrays AlwaysEmbed and NeverEmbed and image parameter dictionaries ColorACSImageDict, ColorACSImageDict, ColorImageDict, GrayACSImageDict, GrayImageDict, MonoImageDict cannot be specified on the ps2pdf command line. To specify these, you must use PostScript, either by including it in the PostScript source or by passing the -c command-line parameter to ghostscript as described in Limitations below. For example, including the PostScript string in your file in.ps:

<</AlwaysEmbed [/Helvetica /Times-Roman]>> setdistillerparams
is equivalent to invoking:
gs -dBATCH -dSAFER -DNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=out.pdf -c '.setpdfwrite <</AlwaysEmbed [/Helvetica /Times-Roman]>> setdistillerparams' -f in.ps
or using ps2pdf with the extra parameters in a file:
ps2pdf @params.in out.pdf
where the file params.in contains:
-c '<</AlwaysEmbed [/Helvetica /Times-Roman]>> setdistillerparams' -f in.ps

(note 14) The default value of CompressPages is false for ps2write and eps2write.

Color Conversion and Management

As of the 9.11 pre-release, the color management in the pdfwrite family has been substantially altered so that it now uses the same Color Management System as rendering (the default is LCMS2). This considerably improves the color handling in both pdfwrite and ps2write, particularly in the areas of Separation and DeviceN color spaces, and Indexed color spaces with images. Despite lengthy careful testing it is possible that there will be bugs in this initial implementation and so the following switch is available.

-dPDFUseOldCMS=boolean
The old (non-ICC) colour management code has now been removed and this switch no longer has any effect.

The ColorConversionStrategy switch can now be set to LeaveColorUnchanged, Gray, RGB, CMYK or UseDeviceIndependentColor. Note that, particularly for ps2write, LeaveColorUnchanged may still need to convert colors into a different space (ICCbased colors cannot be represented in PostScript for example). ColorConversionStrategy can be specified either as; a string by using the -s switch (-sColorConversionStrategy=RGB) or as a name using the -d switch (-dColorConversionStrategy=/RGB).

ps2write cannot currently convert into device-independent color spaces, and so UseDeviceIndependentColorshould not be used with ps2write (oe eps2write).

All other color spaces are converted approproately. Separation and DeviceN spaces will be preserved if possible (ps2write cannot preserve DeviceN) and if the alternate space is not appropriate a new alternate space will be created. Eg a [/Separation (MyColor) /DeviceRGB {...}] when the ColorConversionStrategy is set to CMYK would be converted to [/Separation (MyColor) /DeviceCMYK {...}] The new tint transform would be created by sampling the original tint transform, converting the RGB values into CMYK, and then creating a function to linearly interpolate between those values.

Setting page orientation

By default Ghostscript determines viewing page orientation based on the dominant text orientation on the page. Sometimes, when the page has text in several orientations or has no text at all, wrong orientation can be selected.

Acrobat Distiller parameter AutoRotatePages controls the automatic orientation selection algorithm. On Ghostscript, besides input stream, Distiller parameters can be given as command line arguments. For instance: -dAutoRotatePages=/None or /All or /PageByPage.

When there is no text on the page or automatic page rotation is set to /None an orientation value from setpagedevice is used. Valid values are: 0 (portrait), 3 (landscape), 2 (upside down), and 1 (seascape). The orientation can be set from the command line as -c "<</Orientation 3>> setpagedevice" using Ghostscript directly but cannot be set in ps2pdf. See Limitations below.

Ghostscript passes the orientation values from DSC comments to the pdfwrite driver, and these are compared with the auto-rotate heuristic. If they are different then the DSC value will be used preferentially. If the heuristic is to be preferred over the DSC comments then comment parsing can be disabled by setting -dParseDSCComments=false.


Controls and features specific to PostScript and PDF input

-dPDFSETTINGS=configuration
Presets the "distiller parameters" to one of four predefined settings:

NB Adobe has recently changed the names of the presets it uses in Adobe Acrobat Distiller, in order to avoid confusion with earlier versions we do not plan to change the names of the PDFSETTINGS parameters. The precise value for each control is listed in the table above.

Please be aware that the /prepress setting does not indicate the highest quality conversion. Using any of these presets will involve altering the input, and as such may result in a PDF of poorer quality (compared to the input) than simply using the defaults. The 'best' quality (where best means closest to the original input) is obtained by not setting this parameter at all (or by using /default).
The PDFSETTINGS presets should only be used if you are sure you understand that the output will be altered in a variety of ways from the input. It is usually better to adjust the controls individually (see the table below) if you have a genuine requirement to produce, for example, a PDF file where the images are reduced in resolution.

Controls and features specific to PCL and PXL input

Many of the controls used for distiller pararameters can be used on the command line with the -d or -s switches, and these will work correctly with PCL or PXL input. However, some controls (eg /NeverEmbed) do not take simple numeric or string arguments, and these cannot be set from the command line. When the input is PostScript or PDF we can use the -c and -f switches to send PostScript through the interpreter to control these parameters, but clearly this is not possible when the intepreter does not understand PostScript. In addition some features are controlled using the PostScript pdfmark operator and again that clearly is not possible unless we are using a PostScript interpreter to read the input.

To overcome this new, GhostPCL-specific, PJL parameters have been added. These parameters are defined as PDFMARK and SETDISTILLERPARAMS. In order to reduce confusion when using PostScript and PCL as inputs these PJL parameters take essentially the same PostScript constructs as the corresponding PostScript operators pdfmark and setdistillerparams. However it is important to realise that these are not processed by a full PostScript interpreter, and there are syntactic rules which must be followed carefully when using these parameters.

You cannot use arbitrary PostScript operators, only boolean, number, name, string, array and dictionary objects are supported (but see PUTFILE later). All tokens must be separated by white space, so while this [/Test(string)] is perfectly valid in PostScript, you must instead write it as [ /Test (string) ] for PJL parsing. All PDFMARK and SETDISTILLERPARAMS must be set as DEFAULT, the values must be on a single line, and delimited by "".

pdfmarks sometimes require the insertion of file objects (especially for producton of PDF/A files) so we must find some way to handle these, ths is done (for the pdfmark csae only) by defining a special (non-standard) pdfmark name PUTFILE, this simply takes the preceding string, and uses it as a fully qualified path to a file. Any further pdfmark operations can then use the named object holding the file to access it.

The easiest way to use these parameters is to create a 'settings' file, put all the commands in it, and then put it on the command line immediately before the real input file. For example:

./gpcl6 -sDEVICE=pdfwrite -dPDFA=1 -dCompressPages=false -dCompressFonts=false -sOutputFile=./out.pdf ./pdfa.pjl ./input.pcl

Where pdfa.pjl contains the PJL commands to create a PDF/A-1b file (see example below).

Example creation of a PDF/A output file

For readability the line has been bisected, when used for real this must be a single line. The 'ESC' represents a single byte, value 0x1B an escape character in ASCII.

ESC%-12345X
@PJL DEFAULT PDFMARK = "
[ /_objdef {icc_PDFA} /type /stream /OBJ pdfmark
[ {icc_PDFA} << /N 3 >> /PUT pdfmark
[ {icc_PDFA} (/ghostpdl/iccprofiles/default_rgb.icc) /PUTFILE pdfmark
[ /_objdef {OutputIntent_PDFA} /type /dict /OBJ pdfmark
[ {OutputIntent_PDFA} << /S /GTS_PDFA1 /Type /OutputIntent /DestOutputProfile {icc_PDFA} /OutputConditionIdentifier (sRGB) >> /PUT pdfmark
[ {Catalog} << /OutputIntents [{OutputIntent_PDFA}] >> /PUT pdfmark
[ /Author (Ken) /Creator (also Ken) /Title (PDF/A-1b) /DOCINFO pdfmark
"

Example using DISTILLERPARAMS to set the quality of JPEG compression.

ESC%-12345X @PJL DEFAULT SETDISTILLERPARAMS = "<< /ColorImageDict << /QFactor 0.7 /Blend 1 /HSamples [ 2 1 1 2 ] /VSamples [ 2 1 1 2 ] >> >>"


PDF file output

-dMaxInlineImageSize=integer
Specifies the maximum size of an inline image, in bytes. For images larger than this size, ps2pdf will create an XObject instead of embedding the image into the context stream. The default value is 4000. Note that redundant inline images must be embedded each time they occur in the document, while multiple references can be made to a single XObject image. Therefore it may be advantageous to set a small or zero value if the source document is expected to contain multiple identical images, reducing the size of the generated PDF.
-dDoNumCopies
When present, causes pdfwrite to use the #copies or /NumCopies entry in the page device dictionary to duplicate each page in the output PDF file as many times as the 'copies' value. This is intended for use by workflow applications like CUPS and should not be used for generating general purpose PDF files. In particular any pdfmark operations which rely on page numbers, such as Link or Outline annotations will not work correctly with this flag.
-dDetectDuplicateImages
Takes a Boolean argument, when set to true (the default) pdfwrite will compare all new images with all the images encountered to date (NOT small images which are stored in-line) to see if the new image is a duplicate of an earlier one. If it is a duplicate then instead of writing a new image into the PDF file, the PDF will reuse the reference to the earlier image. This can considerably reduce the size of the output PDF file, but increases the time taken to process the file. This time grows exponentially as more images are added, and on large input files with numerous images can be prohibitively slow. Setting this to false will improve performance at the cost of final file size.
-dFastWebView
Takes a Boolean argument, default is false. When set to true pdfwrite will reorder the output PDF file to conform to the Adobe 'linearised' PDF specification. The Acrobat user interface refers to this as 'Optimised for Fast Web Viewing'. Note that this will cause the conversion to PDF to be slightly slower and will usually result in a slightly larger PDF file.
This option is incompatible with producing an encrypted (password protected) PDF file.
-dPDFDontUseFontObjectNum
Certain authoring tools produce PDF files containing subset fonts where the choice of the subset prefix is sub-optimal, either sequentail or otherwise not based on the font content. This is not a problem when dealing with a single PDF file, as the PDF object number of the font is guaranteed unique in the file, so the correct font will always be used. However, if we are supplied with two or more PDF files, we have seen cases where the font names are not unique (poor subset prefix selection), which can lead to Ghostscript deciding that two different fonts are in fact the same, and causing incorrect output with the pdfwrite family of devices. A recent change in the PDF interpreter (and the pdfwrite device) now creates a XUID for each font, based on the input filename and the PDF object number, whch makes it quite unlikely that ths situation can now arise. However, certain poorly written PDF files contain multiple copies of the same font, and now that we consider fonts with differing numbers to be different fonts, pdfwrite emits these fonts multple times, just as the input did. This can lead to a small increase in the size of the final PDF file (but no other problems). If this should happen, and is important to you, you can use this switch to disable the use of the object number (and filename) in determining the uniqueness of fonts.

The following options are useful for creating PDF 1.2 files:

-dPatternImagemask=boolean
With CompatibilityLevel < 1.3 it specifies whether the target viewer handles ImageMask with a pattern color. Some old viewers, such as Ghostscript 3.30 fail with such constructs. Seting this option to false, one can get more compatibility, but the mask interpolation is lost. With CompatibilityLevel ≥ 1.3 this option is ignored. Default value is false.
-dMaxClipPathSize=integer
Specifies the maximum number of elements in the clipping path that the target viewer can handle. This option is used only with CompatibilityLevel < 1.3 and PatternImagemask=false, and only when converting a mask into a clipping path. If the clipping path exceeds the specified size, the masked image and the clipping path is decomposed into smaller images. The value of the option counts straight path segments (curved segments are not used for representing a mask). Default value is 12000.
-dMaxShadingBitmapSize=integer
Specifies the maximum number of bytes allowed for representing a shading as a bitmap. If a shading exceeds this value, the resolution of the output bitmap is reduced to fit into the specified number of bytes. Note that the number of bytes depends on the number of color components in ProcessColorModel or ColorConverionStrategy, assumes 8 bits per sample, and doesn't consider image compression or downsampling. The image is rendered at the current resolution as specified by -r or the default of 720 dpi. Default value is 256000. In general larger values will result in higher quality, but the output file size may increase dramatically, particularly with shadings which cover large areas. Shadings hsould generally only be rendered to images if CompatibilityLevel is 1.2 or less or if ColorCoversionStrategy specifies a color space differnt to that of the shading.
-dHaveTrueTypes=boolean
With CompatibilityLevel < 1.3 it specifies whether the target viewer can handle TrueType fonts. If not, TrueType fonts are converted into raster fonts with resolution specified in HWResolution. Note that large text at higher resolutions results in very large bitmaps which are likely to defeat caching in many printers. As a result the text is emitted as simple images rather than as a (type 3) bitmap font. The PostScript user parameter MaxFontItem can be used to increase the maximum size of a cache entry which will increase the size/resolution of the text which can be stored in a font. With CompatibilityLevel ≥ 1.3 this option is ignored. Default value is true.

The following options are useful for creating PDF 1.3 files:

-dHaveTransparency=boolean
With CompatibilityLevel ≥ 1.4 it specifies whether the target viewer can handle PDF 1.4 transparency objects. If not, transparency objects are converted into plain images. Default value is true.

The following option specifies creation of a PDF/X-3 file

-dPDFX=boolean
Specifies the generated document is to follow the PDF/X-3 standard. When true, a DefaultRGB ColorSpace resource must be defined, and options NOSUBSTDEVICECOLORS, NOCIE must not be specified. Default value is false.

The pdfwrite device does not currently support PDF/X versions other than 3.

When generating a PDF/X-3 document, Ghostscript performs the following special actions to satisfy the PDF/X-3 standard :

The following switches are used for creating encrypted documents :

-sOwnerPassword=string
Defines that the document be encrypted with the specified owner password.
-sUserPassword=string
Defines the user password for opening the document. If empty, the document can be opened with no password, but the owner password is required to edit it.
-dPermissions=number
Defines the PDF permissions flag field. Negative values are allowed to represent unsigned integers with the highest bit set. See the PDF Reference manual for the meaning of the flag bits.
-dEncryptionR=number
Defines the encryption method revision number - either 2 or 3.
-dKeyLength=number
Defines the length (in bits) of the encryption key. Must be a multiple of 8 in the interval [40, 128]. If the length isn't 40, -dEncryptionR must be 3.

The following switches are used for generating metadata according to the Adobe XMP specification :

-sDocumentUUID=string
Defines a DocumentID to be included into the document Metadata. If not specified, Ghostscript generates an UUID automatically. Otherwise the specified string is copied into the document without checking its syntax or consistence.

Note that Adobe XMP specification requires DocumentID must be same for all versions of a document. Since Ghostscript does not provide a maintenance of document versions, users are responsible to provide a correct UUID through this parameter.

Note that Ghostscript has no assess to the host node ID due to a minimization of platform dependent modules. Therefore it uses an MD5 hash of the document contents for generating UUIDs.

-sInstanceUUID=string
Defines a instance ID to be included into the document Metadata. If not specified, Ghostscript generates an UUID automatically. Otherwise the specified string is copied into the document without checking its syntax or consistence.

Note that Adobe XMP specification requires instance ID must be inique for all versions of document. This parameter may be used to disable an unique ID generation for a debug purpose.

When none of DocumentUUID and InstanceUUID are specified, the generated DocumentID appears same as instance ID.

-sDocumentTimeSeq=integer
Defines an integer to be used as a deconflictor for generating UUIDs, when several invokations of Ghostscript create several PDF documents within same clock quantum (tick). Mainly reserved for very fast computers and/or multhithreading applications, which may appear in future. If both DocumentUUID and InstanceUUID are specified, DocumentTimeSeq is ignored.
-sDSCEncoding=string
Defines the name of a Postscript encoding in which DSC comments in the source document are encoded. If specified, the comments are converted from that encoding into Unicode UTF-8 when writing Metadata. If not specified, the comments are copied to Metadata with no conversion. Note that Adobe Distiller for Windows uses the default locale's code page for this translation, so it's result may differ from Ghostscript. Adobe Acrobat appears to use PDFDocEncoding when displaying document's properties, so we recommend this value.

PostScript file output

The ps2write device handles the same set of distiller parameters as are handled by the pdfwrite device (and 2 unique extensions, see below).

The option -dMaxInlineImageSize=integer must not be used with ps2write as all images are inline in PostScript.

There are also two additional (not Adobe-standard) Distiller parameters, specific to ps2write:

/PSDocOptions string
No default value. If defined, the contents of the string will be emitted in the output PostScript prolog enclosed within %%BeginSetup and %%EndSetup comments. This is intended as a means of introducing device-specific document wide setup or configuration options into the output. Default media selection, printer resolution etc might be included here.
/PSPageOptions array of strings
No default value. If defined, the contents of the strings in the array will be emitted in the output PostScript at the start of each page, one string per page, enclosed within %%BeginPageSetup and %%EndPageSetup comments. This is intended as a means of introducing device-specific setup or configuration options into the output on a page by page basis. The strings are used from the array sequentially, if there are more pages than strings then we 'wrap round' and start again with the first string. This makes it convenient to do setup for even/odd pages by simply including 2 strings in the array.

NB the strings contained in PSDocOptions, and the PSPageOptions array, are written verbatim to the output. No error checking is (or can be) performed on these strings and it is the users responsibility to ensure they contain well formed PostScript which does not cause errors on the target device.

There are also the following ps2write specific options :

-dProduceDSC=boolean
Default value is true. When this value is true the output PostScript file will be constructed in a way which is compatible with the Adobe Document Structuring Convention, and will include a set of comments appropriate for use by document managers. This enables features such as page extraction, N-up printing and so on to be performed. When set to false, the output file will not be DSC-compliant. Older versions of Ghostscript cannot produce DSC-compliant output from ps2write, and the behviour for these older versions matches the case when ProduceDSC is false.
-dCompressEntireFile=boolean
When this parameter is true, the LZWEncode and ASCII85Encode filters will be applied to the entire output file. In this case CompressPages should be false to prevent a dual compression. When this parameter is false, these filters will be applied to the initial procset only, if CompressPages is true. Default value is false.

Note: It is not possible to set CompressEntireFile when ProduceDSC is true as a single compressed object cannot conform to the DSC. It is possible to set CompressPages which will also compress the ps2write ProcSet.

Controlling device-specific behavior

A few options can be used to influence the behavior of a printer or PostScript interpreter that reads the result of ps2ps2. All of these options are incompatible with DSC-compliant PostScript, in order to use any of them ProduceDSC must be set to false.

-dRotatePages=boolean.
The printer will rotate pages for a better fit with the physical size. Default value : false. Must be false if -dSetPageSize=true.
-dFitPages=boolean.
The printer will scale pages down to better fit the physical page size. The rendering quality may be poor due to the scaling, especially for fonts which Ghostscript had converted into bitmaps (see the ps2write device parameter HaveTrueTypes; See Options about the PageSize entry of the Policies dictionary while the conversion step). Default value : false. Must be false if -dSetPageSize=true or -dCenterPages=true.
-dCenterPages=boolean.
The printer will center the page image on the selected media. Compatible with -dRotatePages=true, which may rotate the image on the media if it fits better, and then center it. Default value : false. Must be false if -dSetPageSize=true or -dFitPages=true.
-dSetPageSize=boolean.
The printer will try to set page size from the job. Only use with printers which can handle random PageSize. Defaults to true, must be false if -dRotatePages=true, -dCenterPages=true or -dFitPages=true.
-dDoNumCopies=boolean.
The PostScript emitted by ps2write will try to use copypage to create the number of copies originally requested. Note that this relies on the level 2 semantics for copypage and will not reliably work on language level 3 devices (such as Ghostscript itself). Defaults to false. This flag is not compatible with the ProduceDSC flag which will take precedence if set.

These correspond to keys in the Postscript userdict of the target printer's virtual memory to control its behavior while executing a job generated with ps2write.

These keys can be set when executing using the ps2write device, this 'fixes' the resulting behaviour according to which key has been set. If these keys are not defined during conversion, the resulting PostScript will not attempt any form of media selection. In this case the behaviour can then be modified by setting the keys, either by modifying the resulting PostScript or setting the values in some other manner on the target device.

See also the distiller params PSDocOptions and PSPageOptions mentioned above.


Encapsulated PostScript (EPS) file output

The eps2write device is the same as the ps2write device, except that it produces Encapsulated PostScript, which is intended to be imported into another document and treated as a 'black box'. There are certain restrictions which EPS files must follow, the primary one being tht they must be DSC conformant. This means that you must not set -dProduceDSC to false.

In addition EPS files may only contain a single page and may not contain device-specific PostScript. You should therefore not use the PSDocOptions or PSPageOptions or any of the switches noted in the ps2write section above under Controlling device specific behaviour


Creating a PDF/X-3 document

To create a PDF/X-3 document from a Postscript or a PDF file, you should :

As mentioned above, the PDF/X definition file provides special information, which the PDF/X-3 standard requires. You can find a sample file in gs/lib/PDFX_def.ps, and edit it according to your needs. The file follows Postscript syntax and uses the operator pdfmark to pass the special information. To ease customisation the lines likely to need editing in the sample file are marked with the comment % Customize. They are explained below.

OutputCondition string
Defines an OutputCondition value for the output intent dictionary.
OutputConditionIdentifier string
Defines an OutputConditionIdentifier value for the output intent dictionary.
ICCProfile string
May be omited if OutputConditionIdentifier specifies a registed identifier of characterized printing condition (see http://www.color.org/IPA_2003-11_PDFX.pdf). Defines a file name of an ICC profile file to be included into the output document. You may specify either an absolute file name, or a relative path from the working directory.
Title string
Defines the document title. Only useful if the source Postscript file doesnt define a title with DSC comments. Otherwise remove entire line from definition file.
Info string
Defines an Info value for the output intent dictionary.

Ghostscript distribution does not contain an ICC profile to be used for creating a PDF/X-3 document. Users should either create an appropriate one themselves, or use one from a public domain, or create one with the PDF/X-3 inspector freeware.

The PDF/X-3 standard requires a TrimBox entry to be written for all page descriptions. This is an array of four offsets that specify how the page is to be trimmed after it has been printed. It is set to the same as MediaBox by default unless the PDFXTrimBoxToMediaBoxOffset distiller parameter is present. It accepts offsets to the MediaBox as an array [left right top bottom], e.g., the PostScript input code << /PDFXTrimBoxToMediaBoxOffset [10 20 30 40] >> setdistillerparams specifies that 10 points will be trimmed at the left, 20 points at the right, 30 points at the top, and 40 points at the bottom.

Another page entry is the BleedBox. It gives the area of the page to which actual output items may extend; cut marks, color bars etc. must be positioned in the area between the BleedBox and the MediaBox. The TrimBox is always contained within the BleedBox. By default, the PDFXSetBleedBoxToMediaBox distiller parameter is true, and the BleedBox is set to the same values as the MediaBox. If it is set to false, the PDFXBleedBoxToTrimBoxOffset parameter gives offset to the TrimBox. It accepts a four-value array in the same format as the PDFXTrimBoxToMediaBoxOffset parameter.

Here is a sample command line to invoke Ghostscript for generating a PDF/X-3 document :

gs -dPDFX -dBATCH -dNOPAUSE -sColorConverionStrategy=CMYK -sDEVICE=pdfwrite -sOutputFile=out-x3.pdf PDFX_def.ps input.ps

Please also see the PDFACompatibilityPolicy control described under "Creating a PDF/A document" below. The same control is now used to specify the desired behaviour when an input file cannot be converted 'as is' into a PDF/X file.


Creating a PDF/A document

To create a PDF/A document, please follow the instructions for creating a PDF/X-3 document, with the following exceptions :

There is one additional control for PDF/A output:
PDFACompatibilityPolicy integer
When an operation (eg pdfmark) is encountered which cannot be emitted in a PDF/A compliant file, this policy is consulted, there are currently three possible values:
0 - (default) Include the feature or operation in the output file, the file will not be PDF/A compliant. Because the document Catalog is emitted before this is encountered, the file will still contain PDF/A metadata but will not be compliant. A warning will be emitted in this case.
1 - The feature or operation is ignored, the resulting PDF file will be PDF/A compliant. A warning wil be emitted for every elided feature.
2 - Processing of the file is aborted with an error, the exact error may vary depending on the nature of the PDF/A incompatibility.
Here is a sample command line to invoke Ghostscript for generating a PDF/A document :
gs -dPDFA=1 -dBATCH -dNOPAUSE -sColorConversionStrategy=RGB -sDEVICE=pdfwrite -sOutputFile=out-a.pdf PDFA_def.ps input.ps


Ghostscript PDF Printer Description

To assist with creating a PostScript file suitable for conversion to PDF, ghostscript includes ghostpdf.ppd, a PostScript Printer Description (PPD) file. This allows some distiller parameters to be set when a PostScript file is generated.

Windows XP or 2000

To install a "Ghostscript PDF" printer on Windows XP, select the Windows Control Panel, Printers and Faxes, Add a Printer, Local Printer, Use port FILE: (Print to File), Have Disk..., select the directory containg ghostpdf.ppd and ghostpdf.inf, select "Ghostscript PDF", Replace existing driver (if asked), and answer the remaining questions appropriately. After installing, open the "Ghostscript PDF" properties, select the Device Settings tab, set "Mimimum Font Size to Download as Outline" to 0 pixels.

To set distiller parameters, select the "Ghostscript PDF" Printing Preferences, then the Advanced button. The PDF settings are under "Printer Features".


pdfmark extensions

In order to better support the ZugFERD electronic invoice standard (http://www.ferd-net.de/front_content.php?idcat=231&changelang=4) and potentially other standards in the future, a new non-standard pdfmark has been defined for use by pdfwrite.

This pdfmark allows additional Metadata to be defined which will be inserted into the Metadata generated by the pdfwrite device. This is necesary because the standard requires a PDF/A-3 file be produced, with an extension schema (and some additional XML data) contained within the Metadata referenced from the Catalog object.

While it would be possible to use the existing Metadata pdfmark to write a completely new set of metadata into the Catalog, creating a conformant set of XML, with all the information synchronised with the /Info dictionary would be challenging, this pdfmark allows the pdfwrite device to generate all the normal information leaving the user with only the task of specifying the additional data.

[ /XML (string continaing additional XMP data) /Ext_Metadata pdfmark


Limitations

The pdfwrite family will sometimes convert input constructs to lower-level ones, even if a higher-level construct is available. For example, if the PostScript file uses charpath to set a clipping path consisting of text, ps2pdf may write the clipping path as a path in the PDF file, rather than as text, even though PDF is able to express clipping with text. This is only a performance issue, and will be improved incrementally over time.

Some applications, such as HIGZ, produce PostScript files that use ridiculously large coordinates. On such files, pdfwrite may cause a limitcheck error. If this occurs, try reducing the default internal resolution of 720 dpi by using the -r switch, e.g., ps2pdf -r300 somefile.ps.

pdfwrite ignores the PDF 1.3 (Acrobat 4.x) pdfmarks related to document content structure: StRoleMap, StClassMap, StPNE, StBookmarkRoot, StPush, StPop, StPopAll, StBMC, StBDC, EMC, StOBJ, StAttr, StStore, StRetrieve, NamespacePush, NamespacePop, and NI. While this causes some structural information to be omitted from the output file, the displayed and printed output are normally not affected.


Copyright © 2000-2006 Artifex Software, Inc. All rights reserved.

This software is provided AS-IS with no warranty, either express or implied. This software is distributed under license and may not be copied, modified or distributed except as expressly authorized under the terms of that license. Refer to licensing information at http://www.artifex.com/ or contact Artifex Software, Inc., 7 Mt. Lassen Drive - Suite A-134, San Rafael, CA 94903, U.S.A., +1(415)492-9861, for further information.

Ghostscript version 9.20, 26 September 2016