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Optimize pixels rotation in wxImage::Rotate90().

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Rotate the image by entire strips instead of doing it pixel by pixel.

This seems to result in about 50% performance gain.

Closes #12739.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66309 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Vadim Zeitlin
2010-12-03 12:40:03 +00:00
parent 944f641cf9
commit 4776c0b783
1 changed files with 24 additions and 11 deletions
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35
src/common/image.cpp
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@@ -1089,24 +1089,37 @@ wxImage wxImage::Rotate90( bool clockwise ) const
}
unsigned char *data = image.GetData();
const unsigned char *source_data = M_IMGDATA->m_data;
unsigned char *target_data;
for (long j = 0; j < height; j++)
// we rotate the image in 21-pixel (63-byte) wide strips
// to make better use of cpu cache - memory transfers
// (note: while much better than single-pixel "strips",
// our vertical strips will still generally straddle cachelines)
for (long ii = 0; ii < width; )
{
for (long i = 0; i < width; i++)
long next_ii = wxMin(ii + 21, width);
for (long j = 0; j < height; j++)
{
if ( clockwise )
const unsigned char *source_data
= M_IMGDATA->m_data + (j*width + ii)*3;
for (long i = ii; i < next_ii; i++)
{
target_data = data + (((i+1)*height) - j - 1)*3;
if ( clockwise )
{
target_data = data + (((i+1)*height) - j - 1)*3;
}
else
{
target_data = data + ((height*(width - 1 - i)) + j)*3;
}
memcpy( target_data, source_data, 3 );
source_data += 3;
}
else
{
target_data = data + ((height*(width-1)) + j - (i*height))*3;
}
memcpy( target_data, source_data, 3 );
source_data += 3;
}
ii = next_ii;
}
const unsigned char *source_alpha = M_IMGDATA->m_alpha;