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Doc: Improved explanation of quality setting in QImageReader/Writer

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Explanation was somewhat inprecise and incomplete.

Task-number: QTBUG-41358
Change-Id: Iae52c30868ca48a49eac76d6979a9b02c24a7d49
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
This commit is contained in:
aavit 2014-10-14 12:18:08 +02:00
parent d0402bed6f
commit ff98c44060
2 changed files with 25 additions and 15 deletions
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23
src/gui/image/qimagereader.cpp
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@ -877,15 +877,22 @@ QString QImageReader::fileName() const
/*!
\since 4.2
This is an image format specific function that sets the quality
level of the image to \a quality. For image formats that do not
support setting the quality, this value is ignored.
Sets the quality setting of the image format to \a quality.
The value range of \a quality depends on the image format. For
example, the "jpeg" format supports a quality range from 0 (low
quality, high compression) to 100 (high quality, low compression).
Some image formats, in particular lossy ones, entail a tradeoff between a)
visual quality of the resulting image, and b) decoding execution time.
This function sets the level of that tradeoff for image formats that
support it.
\sa quality()
In case of scaled image reading, the quality setting may also influence the
tradeoff level between visual quality and execution speed of the scaling
algorithm.
The value range of \a quality depends on the image format. For example,
the "jpeg" format supports a quality range from 0 (low visual quality) to
100 (high visual quality).
\sa quality() setScaledSize()
*/
void QImageReader::setQuality(int quality)
{
@ -895,7 +902,7 @@ void QImageReader::setQuality(int quality)
/*!
\since 4.2
Returns the quality level of the image.
Returns the quality setting of the image format.
\sa setQuality()
*/

17
src/gui/image/qimagewriter.cpp
View File

@ -434,13 +434,16 @@ QString QImageWriter::fileName() const
}
/*!
This is an image format specific function that sets the quality
level of the image to \a quality. For image formats that do not
support setting the quality, this value is ignored.
Sets the quality setting of the image format to \a quality.
The value range of \a quality depends on the image format. For
example, the "jpeg" format supports a quality range from 0 (low
quality, high compression) to 100 (high quality, low compression).
Some image formats, in particular lossy ones, entail a tradeoff between a)
visual quality of the resulting image, and b) encoding execution time and
compression level. This function sets the level of that tradeoff for image
formats that support it. For other formats, this value is ignored.
The value range of \a quality depends on the image format. For example,
the "jpeg" format supports a quality range from 0 (low visual quality, high
compression) to 100 (high visual quality, low compression).
\sa quality()
*/
@ -450,7 +453,7 @@ void QImageWriter::setQuality(int quality)
}
/*!
Returns the quality level of the image.
Returns the quality setting of the image format.
\sa setQuality()
*/