Function Reference
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If no output intent was specified, Adobe's Acrobat or Reader simulate a default CMYK color space
as output color space if transparency is used on a page, also if the page uses RGB colors only! This
differs from normal RGB files which use no transparency and causes often unwanted color changes.
Note that this rule applies also to images which contain an alpha channel!
If the PDF file uses RGB colors only, then attach an sRGB profile to the file. Such a profile is very
small but it makes a huge difference whether the profile is present or not.
Remarks:
Transparency and blend modes are discussed in detail in the section PDF Transparency.
Return values:
If the function succeeds the return value is the extended graphics state handle, a value greater or
equal zero. If the function fails the return value is a negative error code.
