From a9c46bc288d23c95fd08ee66493cb07be074f02e Mon Sep 17 00:00:00 2001 From: Andrew Murray Date: Wed, 28 Dec 2022 10:22:10 +1100 Subject: [PATCH] Document "transparency" info key --- docs/handbook/concepts.rst | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/docs/handbook/concepts.rst b/docs/handbook/concepts.rst index f3fa1f2b1..f7bc9396b 100644 --- a/docs/handbook/concepts.rst +++ b/docs/handbook/concepts.rst @@ -111,6 +111,18 @@ the file format handler (see the chapter on :ref:`image-file-formats`). Most handlers add properties to the :py:attr:`~PIL.Image.Image.info` attribute when loading an image, but ignore it when saving images. +Transparency +------------ + +If an image does not have an alpha band, transparency may be specified in the +:py:attr:`~PIL.Image.Image.info` attribute with a "transparency" key. + +Most of the time, the "transparency" value is a single integer, describing +which pixel value is transparent in an "1", "L", "I" or "P" mode image. +However, PNG images may have three values, one for each channel in an "RGB" +mode image, or can have a byte string for a "P" mode image, to specify the +alpha value for each palette entry. + Orientation -----------