PDF/X标准是由国际标准化组织(ISO)定义的。应用于图形内容交换；在印刷出版工作流程中广泛使用的标准有以下几种PDF/X格式：PDF/X-1a、PDF/X-3和PDF/X-4(2008)。PDF/X的目的在于为设计员、绘图员、工程师和图像艺术家提供一种可为任何服务提供者正确打印的电子文件格式。PDF/X使保持完全一致性成为可能，即使文件被人们在多处位置，用不同的机器处理，也一样。
PDF/X标准判断如下：
pdf_version：PDF版本号
format_name：GTS_PDFXConformance
xmp_file：XMP
gts_flag：OutputIntent字典中的子类型“/S”
gray_scale：灰度
cmyk_colors：CMYK
spot_colors：spot
rgb_colors：rgb
calibrated_rgb_colors：calrgb
cielab_colors：lab
internal_icc_profiles：内嵌icc profile
inject_metadata：metadata
jbig2_compression：jbig2压缩
include_intents：intents对象
optional_content：OptionalContent
transparency：透明度
jpeg2000_compression：jpeg2000压缩
object_compression：object stream对象压缩
open_prepress_interface：OPI
nchannel_colorspace：NChannel颜色空间
注：“true”表示支持的内容，没有列出的内容，则表示不符合相关标准。
详细：
pdf/x-1a:2001
["pdf/x-1a:2001"] = {
pdf_version = 1.3,
format_name = "PDF/X-1a:2001",
xmp_file = "lpdf-pdx.xml",
gts_flag = "GTS_PDFX",
gray_scale = true,
cmyk_colors = true,
spot_colors = true,
internal_icc_profiles = true,
inject_metadata = function()
addtoinfo("GTS_PDFXVersion","PDF/X-1a:2001")
injectxmpinfo("xml://rdf:RDF","<rdf:Description rdf:about='' xmlns:pdfxid='http://www.npes.org/pdfx/ns/id/'><pdfxid:GTS_PDFXVersion>PDF/X-1a:2001</pdfxid:GTS_PDFXVersion></rdf:Description>",false)
end
},pdf/x-1a:2003
["pdf/x-1a:2003"] = {
pdf_version = 1.4,
format_name = "PDF/X-1a:2003",
xmp_file = "lpdf-pdx.xml",
gts_flag = "GTS_PDFX",
gray_scale = true,
cmyk_colors = true,
spot_colors = true,
internal_icc_profiles = true,
inject_metadata = function()
addtoinfo("GTS_PDFXVersion","PDF/X-1a:2003")
injectxmpinfo("xml://rdf:RDF","<rdf:Description rdf:about='' xmlns:pdfxid='http://www.npes.org/pdfx/ns/id/'><pdfxid:GTS_PDFXVersion>PDF/X-1a:2003</pdfxid:GTS_PDFXVersion></rdf:Description>",false)
end
},pdf/x-3:2002
["pdf/x-3:2002"] = {
pdf_version = 1.3,
format_name = "PDF/X-3:2002",
xmp_file = "lpdf-pdx.xml",
gts_flag = "GTS_PDFX",
gray_scale = true,
cmyk_colors = true,
rgb_colors = true,
calibrated_rgb_colors = true,
spot_colors = true,
cielab_colors = true,
internal_icc_profiles = true,
include_intents = true,
inject_metadata = function()
addtoinfo("GTS_PDFXVersion","PDF/X-3:2002")
end
},pdf/x-3:2003
["pdf/x-3:2003"] = {
pdf_version = 1.4,
format_name = "PDF/X-3:2003",
xmp_file = "lpdf-pdx.xml",
gts_flag = "GTS_PDFX",
gray_scale = true,
cmyk_colors = true,
rgb_colors = true,
calibrated_rgb_colors = true,
spot_colors = true,
cielab_colors = true,
internal_icc_profiles = true,
include_intents = true,
jbig2_compression = true,
inject_metadata = function()
addtoinfo("GTS_PDFXVersion","PDF/X-3:2003")
end
},pdf/x-4
["pdf/x-4"] = {
pdf_version = 1.6,
format_name = "PDF/X-4",
xmp_file = "lpdf-pdx.xml",
gts_flag = "GTS_PDFX",
gray_scale = true,
cmyk_colors = true,
rgb_colors = true,
calibrated_rgb_colors = true,
spot_colors = true,
cielab_colors = true,
internal_icc_profiles = true,
include_intents = true,
optional_content = true,
transparency = true,
jbig2_compression = true,
jpeg2000_compression = true,
object_compression = true,
inject_metadata = function()
injectxmpinfo("xml://rdf:RDF","<rdf:Description rdf:about='' xmlns:pdfxid='http://www.npes.org/pdfx/ns/id/'><pdfxid:GTS_PDFXVersion>PDF/X-4</pdfxid:GTS_PDFXVersion></rdf:Description>",false)
insertxmpinfo("xml://rdf:Description/xmpMM:InstanceID","<xmpMM:VersionID>1</xmpMM:VersionID>",false)
insertxmpinfo("xml://rdf:Description/xmpMM:InstanceID","<xmpMM:RenditionClass>default</xmpMM:RenditionClass>",false)
end
},pdf/x-4p
["pdf/x-4p"] = {
pdf_version = 1.6,
format_name = "PDF/X-4p",
xmp_file = "lpdf-pdx.xml",
gts_flag = "GTS_PDFX",
gray_scale = true,
cmyk_colors = true,
rgb_colors = true,
calibrated_rgb_colors = true,
spot_colors = true,
cielab_colors = true,
internal_icc_profiles = true,
external_icc_profiles = true,
include_intents = true,
optional_content = true,
transparency = true,
jbig2_compression = true,
jpeg2000_compression = true,
object_compression = true,
inject_metadata = function()
injectxmpinfo("xml://rdf:RDF","<rdf:Description rdf:about='' xmlns:pdfxid='http://www.npes.org/pdfx/ns/id/'><pdfxid:GTS_PDFXVersion>PDF/X-4p</pdfxid:GTS_PDFXVersion></rdf:Description>",false)
insertxmpinfo("xml://rdf:Description/xmpMM:InstanceID","<xmpMM:VersionID>1</xmpMM:VersionID>",false)
insertxmpinfo("xml://rdf:Description/xmpMM:InstanceID","<xmpMM:RenditionClass>default</xmpMM:RenditionClass>",false)
end
},pdf/x-5g
["pdf/x-5g"] = {
pdf_version = 1.6,
format_name = "PDF/X-5g",
xmp_file = "lpdf-pdx.xml",
gts_flag = "GTS_PDFX",
gray_scale = true,
cmyk_colors = true,
rgb_colors = true,
calibrated_rgb_colors = true,
spot_colors = true,
cielab_colors = true,
internal_icc_profiles = true,
include_intents = true,
open_prepress_interface = true,
optional_content = true,
transparency = true,
jbig2_compression = true,
jpeg2000_compression = true,
object_compression = true,
inject_metadata = function()
-- todo
end
},pdf/x-5pg
["pdf/x-5pg"] = {
pdf_version = 1.6,
format_name = "PDF/X-5pg",
xmp_file = "lpdf-pdx.xml",
gts_flag = "GTS_PDFX",
gray_scale = true,
cmyk_colors = true,
rgb_colors = true,
calibrated_rgb_colors = true,
spot_colors = true,
cielab_colors = true,
internal_icc_profiles = true,
external_icc_profiles = true,
include_intents = true,
open_prepress_interface = true,
optional_content = true,
transparency = true,
jbig2_compression = true,
jpeg2000_compression = true,
object_compression = true,
inject_metadata = function()
-- todo
end
},pdf/x-5n
["pdf/x-5n"] = {
pdf_version = 1.6,
format_name = "PDF/X-5n",
xmp_file = "lpdf-pdx.xml",
gts_flag = "GTS_PDFX",
gray_scale = true,
cmyk_colors = true,
rgb_colors = true,
calibrated_rgb_colors = true,
spot_colors = true,
cielab_colors = true,
internal_icc_profiles = true,
include_intents = true,
optional_content = true,
transparency = true,
jbig2_compression = true,
jpeg2000_compression = true,
nchannel_colorspace = true,
object_compression = true,
inject_metadata = function()
-- todo
end
},以上列出的item，可以作为判断是否为PDF/X的依据，也可以作为印前检查的判断内容。
还有一些注意事项：
1、PDF/X不支持加密
2、字体嵌入
3、颜色空间限制
4、图片压缩方式限制
5、PDF版本限制
6、透明度限制
7、嵌入文件限制
8、快速web查看限制
9、output intent限制
10、Trapped 接口限制
11、页面box限制
12、注释限制
等等