ghostscript - 在Ghostscript中查询输出设备的默认选项/设置(例如 'pdfwrite'或 'tiffg4')

Question

在this answer to 'GhostScript command line parameters to convert EPS to PDF';据说Ghostscript的pdfwrite设备的默认分辨率是720x720，我最初发现这太不可思议了!

有没有办法列出Ghostscript设备的默认选项？

Answer 1

由于Ghostscript是完善的PostScript解释器，因此您也可以向其发送PostScript代码段，这些代码段不会导致绘制页面元素，而是向其查询其内部状态。

如果您想知道人机界面的默认设置是什么，当您通过gs some.pdf要求它仅在屏幕上显示PDF时，您可以尝试以下操作:

gs \
   -c "currentpagedevice {exch ==only ( ) print == } forall"

在Windows上，它变为:

gswin32c.exe ^
   -c "currentpagedevice {exch ==only ( ) print == } forall"

结果是 /SomeName somevalue对的列表，这些对描述了用于将页面呈现到当前屏幕的设置。

之所以如此，是因为通常显示器是Ghostscript将其输出发送到的默认设备。现在您可能会注意到将看到一个空的Ghostscript窗口弹出，您必须将其关闭....嗯，添加一些避免弹出窗口的选项如何？

gs \
   -o /dev/null \
   -dNODISPLAY \
   -c "currentpagedevice {exch ==only ( ) print == } forall"

或者，在Windows上:

gswin32c.exe ^
   -o nul ^
   -dNODISPLAY ^
   -c "currentpagedevice {exch ==only ( ) print == } forall"

但这将更改查询的返回值，因为您(无意间)更改了输出设备设置:

gs -c "currentpagedevice {exch ==only ( ) print == } forall" | grep Resolution

结果:

HWResolution [86.5426483 86.5426483]
/.MarginsHWResolution [1152.0 1152.0]

比较一下

gs \
   -o /dev/null \
   -dNODISPLAY \
   -c "currentpagedevice {exch ==only ( ) print == } forall" \
| grep Resolution

结果:

/HWResolution [72.0 72.0]
/.MarginsHWResolution [72.0 72.0]

因此，请避免使用此陷阱。几年前，我成功陷入了困境，甚至很长一段时间都没有注意到它。

现在，假设您要查询PDF书写设备的默认设置，请运行以下命令:

gs \
  -o /dev/null \
  -sDEVICE=pdfwrite \
  -c "currentpagedevice {exch ==only ( ) print == } forall" \
| tee ghostscript-pdfwrite-default-pagedevice-settings.txt

现在，您将在* .txt文件中拥有 pdfwrite设备的所有设置。您可以将其与其他一些有趣的Ghostscript设备重复该操作，然后将它们的所有详细差异进行比较:

for _dev in \
  pswrite ps2write pdfwrite \
  tiffg3 tiffg4 tiff12nc tiff24nc tiff32nc tiff48nc tiffsep \
  jpeg jpeggray jpegcmyk \
  png16 png16m png256 png48 pngalpha pnggray pngmono; \
do \
  gs \
    -o /dev/null \
    -sDEVICE=${_dev} \
    -c "currentpagedevice {exch ==only ( ) print == } forall" \
   | sort \
   | tee ghostscript-${_dev}-default-pagedevice-settings.txt; \
done

比较诸如此类的 pswrite和 ps2write设备的设置非常有趣(并且还会发现一个设备可使用的参数，而另一设备则不可用):

sdiff -sbB ghostscript-ps*write-default-pagedevice-settings.txt

更新:

您可能会想到，这也是比较不同Ghostscript版本并跟踪最新版本中不同设备的默认设置可能如何变化的一种好方法。如果您想了解Ghostscript中现在提供的所有新实现的颜色配置文件和ICC支持，这尤其有趣。

此外，为避免某些键值仅返回 -dict-，请使用 ===而不是 ==宏。 ===的行为类似于 ==，但也会打印字典的内容。

因此，这是 pdfwrite设备的示例输出。请记住，Ghostscript的 pdfwrite设备旨在提供与Adobe Acrobat Distiller几乎相同的功能(其附加功能是它不仅接受PostScript作为输入，还接受PDF，因此您可以对现有的PDF文件进行重新整理以进行修复，改善或以其他方式操纵它们)。因此，Ghostscript的 pdfdevice支持原始Distiller还支持的大多数 setdistillerparams运算符:

gs \
  -o /dev/null \
  -sDEVICE=pdfwrite \
  -c "currentpagedevice {exch ==only ( ) print === } forall" \
| sort

/%MediaDestination 0
/%MediaSource 0
/.AlwaysEmbed []
/.HWMargins [0.0 0.0 0.0 0.0]
/.IgnoreNumCopies false
/.LockSafetyParams false
/.MarginsHWResolution [720.0 720.0]
/.MediaSize [612.0 792.0]
/.NeverEmbed [/Courier /Courier-Bold /Courier-Oblique /Courier-BoldOblique /Helvetica /Helvetica-Bold /Helvetica-Oblique /Helvetica-BoldOblique /Times-Roman /Times-Bold /Times-Italic /Times-BoldItalic /Symbol /ZapfDingbats]
/ASCII85EncodePages false
/AllowIncrementalCFF false
/AllowPSRepeatFunctions false
/AlwaysEmbed []
/AntiAliasColorImages false          [*]
/AntiAliasGrayImages false           [*]
/AntiAliasMonoImages false           [*]
/AutoFilterColorImages true
/AutoFilterGrayImages true
/AutoPositionEPSFiles true
/AutoRotatePages /PageByPage
/BeginPage {--.callbeginpage--}
/Binding /Left                       [*]
/BitsPerPixel 24
/BlueValues 256
/CalCMYKProfile (None)               [*]
/CalGrayProfile (None)               [*]
/CalRGBProfile (None)                [*]
/CannotEmbedFontPolicy /Warning      [*]
/CenterPages false
/ColorACSImageDict << /Blend 1 /VSamples [2 1 1 2] /QFactor 0.9 /HSamples [2 1 1 2] >>
/ColorConversionStrategy /LeaveColorUnchanged
/ColorImageDepth -1
/ColorImageDict << /Blend 1 /VSamples [2 1 1 2] /QFactor 0.9 /HSamples [2 1 1 2] >>
/ColorImageDownsampleThreshold 1.5
/ColorImageDownsampleType /Subsample
/ColorImageFilter /DCTEncode
/ColorImageResolution 150
/ColorValues 16777216
/Colors 3
/CompatibilityLevel 1.4
/CompressEntireFile false
/CompressFonts true
/CompressPages true
/ConvertCMYKImagesToRGB false
/ConvertImagesToIndexed true
/CoreDistVersion 5000
/CreateJobTicket false               [*]
/DSCEncodingToUnicode []
/DefaultRenderingIntent /Default
/DetectBlends true                   [*]
/DetectDuplicateImages true
/DeviceGrayToK true
/DeviceLinkProfile ()
/DoNumCopies false
/DoThumbnails false                  [*]
/DocumentTimeSeq 0
/DocumentUUID ()
/DownsampleColorImages false
/DownsampleGrayImages false
/DownsampleMonoImages false
/EmbedAllFonts true
/EmitDSCWarnings false               [*]
/EncodeColorImages true
/EncodeGrayImages true
/EncodeMonoImages true
/EncryptionR 0
/EndPage {--.callendpage--}          [*]
/FirstObjectNumber 1
/FitPages false
/ForOPDFRead false
/GraphicICCProfile ()
/GraphicIntent 0
/GraphicsAlphaBits 1
/GrayACSImageDict << /Blend 1 /VSamples [2 1 1 2] /QFactor 0.9 /HSamples [2 1 1 2] >>
/GrayImageDepth -1
/GrayImageDict << /Blend 1 /VSamples [2 1 1 2] /QFactor 0.9 /HSamples [2 1 1 2] >>
/GrayImageDownsampleThreshold 1.5
/GrayImageDownsampleType /Subsample
/GrayImageFilter /DCTEncode
/GrayImageResolution 150
/GrayValues 256
/GreenValues 256
/HWResolution [720.0 720.0]
/HWSize [6120 7920]
/HaveCIDSystem false
/HaveTransparency true
/HaveTrueTypes true
/HighLevelDevice true
/ImageICCProfile ()
/ImageIntent 0
/ImageMemory 524288                  [*]
/ImagingBBox null
/InputAttributes << 59 << /PageSize [612 792] >> 36 << /PageSize [649 918] >> 13 << /PageSize [595 842] >> 49 << /PageSize [354 499] >> 26 << /PageSize [2004 2835] >> 3 << /PageSize [792 1224] >> 62 << /PageSize [595 792] >> 39 << /PageSize [612 936] >> 16 << /PageSize [297 420] >> 52 << /PageSize [1460 2064] >> 29 << /PageSize [709 1001] >> 6 << /PageSize [2448 3168] >> 42 << /PageSize [396 612] >> 19 << /PageSize [105 148] >> 55 << /PageSize [516 729] >> 32 << /PageSize [2599 3677] >> 9 << /PageSize [1684 2384] >> 45 << /PageSize [1417 2004] >> 22 << /PageSize [1296 1728] >> 58 << /PageSize [612 1008] >> 35 << /PageSize [918 1298] >> 12 << /PageSize [842 1191] >> 48 << /PageSize [499 709] >> 25 << /PageSize [2835 4008] >> 2 << /PageSize [612 792] >> 61 << /PageSize [612 792] >> 38 << /PageSize [323 459] >> 15 << /PageSize [420 595] >> 51 << /PageSize [2064 2920] >> 28 << /PageSize [1001 1417] >> 5 << /PageSize [1585 2448] >> 64 << /PageSize [0 0 524287 524287] >> 41 << /PageSize [283 420] >> 18 << /PageSize [148 210] >> 54 << /PageSize [729 1032] >> 31 << /PageSize [354 499] >> 8 << /PageSize [2384 3370] >> 44 << /PageSize [2004 2835] >> 21 << /PageSize [864 1296] >> 57 << /PageSize [1224 792] >> 34 << /PageSize [1298 1837] >> 11 << /PageSize [1191 1684] >> 47 << /PageSize [709 1001] >> 24 << /PageSize [2592 3456] >> 1 << /PageSize [792 1224] >> 60 << /PageSize [612 792] >> 37 << /PageSize [459 649] >> 14 << /PageSize [595 842] >> 50 << /PageSize [2920 4127] >> 27 << /PageSize [1417 2004] >> 4 << /PageSize [1224 1585] >> 63 << /PageSize [792 1224] >> 40 << /PageSize [612 936] >> 17 << /PageSize [210 297] >> 53 << /PageSize [1032 1460] >> 30 << /PageSize [499 709] >> 7 << /PageSize [2016 2880] >> 43 << /PageSize [2835 4008] >> 20 << /PageSize [648 864] >> 56 << /PageSize [363 516] >> 33 << /PageSize [1837 2599] >> 10 << /PageSize [73 105] >> 46 << /PageSize [1001 1417] >> 23 << /PageSize [1728 2592] >> 0 << /PageSize [612.0 792.0] >> >>
/Install {--.callinstall--}
/InstanceUUID ()
/IsDistiller true
/KeyLength 0
/LZWEncodePages false
/Margins [0.0 0.0]
/MaxClipPathSize 12000
/MaxInlineImageSize 4000
/MaxPatternBitmap 0
/MaxSeparations 3
/MaxShadingBitmapSize 256000
/MaxSubsetPct 100
/MaxViewerMemorySize -1
/MonoImageDepth -1
/MonoImageDict << /K -1 >>
/MonoImageDownsampleThreshold 1.5
/MonoImageDownsampleType /Subsample
/MonoImageFilter /CCITTFaxEncode
/MonoImageResolution 300
/Name (pdfwrite)
/NeverEmbed [/Courier /Courier-Bold /Courier-Oblique /Courier-BoldOblique /Helvetica /Helvetica-Bold /Helvetica-Oblique /Helvetica-BoldOblique /Times-Roman /Times-Bold /Times-Italic /Times-BoldItalic /Symbol /ZapfDingbats]
/NoEncrypt ()
/NoT3CCITT false
/NumCopies null
/OPM 1
/OffOptimizations 0
/Optimize false                      [*]
/OutputAttributes << 0 << >> >>
/OutputDevice /pdfwrite
/OutputFile (/dev/null)
/OutputICCProfile (default_rgb.icc)
/OwnerPassword ()
/PDFA 0
/PDFACompatibilityPolicy 0
/PDFEndPage -1
/PDFStartPage 1
/PDFX false
/PDFXBleedBoxToTrimBoxOffset [0.0 0.0 0.0 0.0]
/PDFXSetBleedBoxToMediaBox true
/PDFXTrimBoxToMediaBoxOffset [0.0 0.0 0.0 0.0]
/PageCount 0
/PageDeviceName null
/PageOffset [0 0]
/PageSize [612.0 792.0]
/ParseDSCComments true
/ParseDSCCommentsForDocInfo true
/PatternImagemask false
/Permissions -4
/Policies << /PolicyReport {--dup-- /.LockSafetyParams --known-- {/setpagedevice --.systemvar-- /invalidaccess signalerror} --if-- --pop--} /PageSize 0 /PolicyNotFound 1 >>
/PreserveCopyPage true               [*]
/PreserveDeviceN true
/PreserveEPSInfo true                [*]
/PreserveHalftoneInfo false          [*]
/PreserveOPIComments true            [*]
/PreserveOverprintSettings true
/PreserveSMask true
/PreserveSeparation true
/PreserveTrMode true
/PrintStatistics false
/ProcessColorModel /DeviceRGB
/ProduceDSC true
/ProofProfile ()
/ReAssignCharacters true
/ReEncodeCharacters true
/RedValues 256
/RenderIntent 0
/RotatePages false
/SeparationColorNames []
/Separations false
/SetPageSize false
/SubsetFonts true
/TextAlphaBits 1
/TextICCProfile ()
/TextIntent 0
/TransferFunctionInfo /Preserve
/UCRandBGInfo /Preserve
/UseCIEColor false
/UseFastColor false
/UseFlateCompression true
/UsePrologue false                   [*]
/UserPassword ()
/WantsToUnicode true
/sRGBProfile (None)                  [*]

[*]注意:

According to the official documentation, the following settings (which are supported by Adobe Acrobat Distiller) currently on Ghostscript can be set and queried, but setting them does have no effect:

/AntiAliasColorImages

/AntiAliasGrayImages

/AntiAliasMonoImages

/AutoPositionEPSFiles

/Binding

/CalCMYKProfile

/CalGrayProfile

/CalRGBKProfile

/CannotEmbedFontPolicy

/ConvertImagesToIndexed

/CreateJobTicket

/DetectBlends

/DoThumbnails

/EmitDSCWarnings

/EndPage

/ImageMemory

/LockDistillerParams

/Optimize

/PreserveCopyPage

/PreserveEPSInfo

/PreserveHalftoneInfo

/PreserveOPIComments

/sRGBProfile

/StartPage

/UsePrologue