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Merge pull request #3384 from radarhere/tutorial

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Improved tutorial
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Hugo 2018-09-29 09:42:11 +03:00 committed by GitHub
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docs/handbook/tutorial.rst
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@ -41,10 +41,10 @@ example, let’s display the image we just loaded::
.. note::
The standard version of :py:meth:`~PIL.Image.Image.show` is not very
efficient, since it saves the image to a temporary file and calls the
:command:`xv` utility to display the image. If you don’t have :command:`xv`
installed, it won’t even work. When it does work though, it is very handy
for debugging and tests.
efficient, since it saves the image to a temporary file and calls a utility
to display the image. If you don’t have an appropriate utility installed,
it won’t even work. When it does work though, it is very handy for
debugging and tests.
The following sections provide an overview of the different functions provided in this library.
@ -183,20 +183,11 @@ Rolling an image
part1 = image.crop((0, 0, delta, ysize))
part2 = image.crop((delta, 0, xsize, ysize))
part1.load()
part2.load()
image.paste(part2, (0, 0, xsize-delta, ysize))
image.paste(part1, (xsize-delta, 0, xsize, ysize))
image.paste(part2, (0, 0, xsize-delta, ysize))
return image
Note that when pasting it back from the :py:meth:`~PIL.Image.Image.crop`
operation, :py:meth:`~PIL.Image.Image.load` is called first. This is because
cropping is a lazy operation. If :py:meth:`~PIL.Image.Image.load` was not
called, then the crop operation would not be performed until the images were
used in the paste commands. This would mean that ``part1`` would be cropped from
the version of ``image`` already modified by the first paste.
For more advanced tricks, the paste method can also take a transparency mask as
an optional argument. In this mask, the value 255 indicates that the pasted
image is opaque in that position (that is, the pasted image should be used as