问题描述
此PDF 由多个原始资料组成.其中五个是包含Alpha通道的PNG.一种是没有Alpha通道的PNG.最后一块是具有透明效果的Photoshop PDF.这些零件使用ABCpdf 9.1进行组装.
This PDF is composed of several source pieces. Five of them are PNGs containing an alpha channel. One is a PNG with no alpha channel. And the last piece is a Photoshop PDF with transparency effects. The pieces were assembled using ABCpdf 9.1.
在Acrobat 9，Foxit Reader和Chrome的浏览器内PDF查看器中，它们可以正确显示，其中Photoshop背景通过alpha通道PNG的透明部分显示，非alpha PNG通过Photoshop的中心显示图片.
On Acrobat 9, Foxit Reader, and Chrome's in-browser PDF viewer, these display correctly, with the Photoshop background showing through the transparent part of the alpha channel PNGs, and the non-alpha PNG showing through the center of the Photoshop image.
在Acrobat X或Acrobat XI上，任何要成为透明区域的东西都是纯白色.如果选中了编辑/首选项/页面显示/显示透明度"网格，则纯白色将变成灰色棋盘.但是背景永远无法显示出来.
On Acrobat X or Acrobat XI, anything that is meant to be a transparent area is instead solid white. If Edit/Preferences/Page Display/Show transparency grid is checked, then the solid white becomes the gray checkerboard. But the background never shows through.
(是的，这些屏幕截图是不同的PDF，并且都与上面链接的PDF不同.但是透明度问题会影响所有这些.)
有人知道为什么会这样做吗?我们构造错了吗?
Does anyone know why it would be doing this? Did we construct it wrong?
推荐答案
文档中的一页具有 Group 条目，该条目定义了页面(透明)组的属性:
The one page in your document has a Group entry defining the attributes of the page (transparency) group:
/Group <<
/I true
/K true
/S /Transparency
/Type /Group
>>
K 条目指定为
由于值为 true ，任何较早的重叠对象(包括您希望通过透明度可见的对象)被剔除，您只会看到白底白字
As the value is true, any earlier overlapping objects (including the objects you want to be visible by transparency) are knocked out and you only see the white page background.
使用/K false可以根据需要渲染图像:
Using /K false instead renders the image as desired:
您在Adobe Reader XI中的原始文档(/K true):
Your original document (/K true) in Adobe Reader XI:
您的文档在Adobe Reader XI中具有禁用的剔除条目(/K false):
Your document with the knockout entry disabled (/K false) in Adobe Reader XI:
有关详细信息，请参见PDF规范 ISO 32000-1
For details cf. the PDF specification ISO 32000-1
- 表30 页面对象页面条目中页面对象中的条目；
- 第11.4.7节页面组中有关页面组的定义；
- 第11.6.6节透明组XObjects 用于页面组字典的条目.
- table 30 Entries in a page object for the page dictionary Group entry;
- section 11.4.7 Page Group for a definition of the page group;
- section 11.6.6 Transparency Group XObjects for the entries of the page group dictionary.
这篇关于PDF中的透明图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！