PDF规格-ExtGState [英] PDF Spec - ExtGState

问题描述

此ExtGState对象对图像有什么作用

What does this ExtGState object do to an image:

<< /Type /ExtGState /TR /Identity >>

我有PDF规范，但还不清楚.显然，这将身份函数(什么是身份矩阵?)从[0.0 1.0]映射到[0.0 1.0](相同)，这没有任何意义.

I have the PDF spec, but it is not clear at all. Apparently this maps the identity function (identity of what? the identity matrix?) from [0.0 1.0] to [0.0 1.0] (the same), which makes no sense.

有人可以向我解释这是什么吗?

Could someone please explain to me what this does?

推荐答案

它指定用于处理颜色或颜色分量(例如，用于伽玛校正)的函数.指定/Identity实际上应该与根本不指定它相同(这是一个可选字段)，因此我怀疑为简单起见，生成PDF的软件总是总是编写默认的ExtGState对象.

It specifies a function that should be used for processing colors or color components (e.g. for gamma correction). Specifying /Identity should actually be the same as not specifying it at all (it's an optional field), so I'd suspect that the software that produced the PDF just always writes a default ExtGState object for simplicity's sake.

有关更多信息，请参见PDF规范中的传递函数"一章.

See the chapter on Transfer Functions in the PDF spec for more information.

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