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Take alpha into account in wxImage::ResampleBicubic()

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Just like in ResampleBox() (see b99ad85b6f),
ResampleBicubic() needs to also weigh pixels by their respective alpha value.

Closes #17748.
This commit is contained in:
Tim Kosse
2016-12-12 10:48:23 +01:00
committed by Vadim Zeitlin
parent 34f8ae85e0
commit 5dc97cc2ca
1 changed files with 34 additions and 9 deletions
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43
src/common/image.cpp
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@@ -1005,23 +1005,48 @@ wxImage wxImage::ResampleBicubic(int width, int height) const
// Create a sum of all velues for each color channel // Create a sum of all velues for each color channel
// adjusted for the pixel's calculated weight // adjusted for the pixel's calculated weight
sum_r += src_data[src_pixel_index * 3 + 0] * pixel_weight;
sum_g += src_data[src_pixel_index * 3 + 1] * pixel_weight;
sum_b += src_data[src_pixel_index * 3 + 2] * pixel_weight;
if ( src_alpha ) if ( src_alpha )
sum_a += src_alpha[src_pixel_index] * pixel_weight; {
const unsigned char a = src_alpha[src_pixel_index];
sum_r += src_data[src_pixel_index * 3 + 0] * pixel_weight * a;
sum_g += src_data[src_pixel_index * 3 + 1] * pixel_weight * a;
sum_b += src_data[src_pixel_index * 3 + 2] * pixel_weight * a;
sum_a += a * pixel_weight;
}
else
{
sum_r += src_data[src_pixel_index * 3 + 0] * pixel_weight;
sum_g += src_data[src_pixel_index * 3 + 1] * pixel_weight;
sum_b += src_data[src_pixel_index * 3 + 2] * pixel_weight;
}
} }
} }
// Put the data into the destination image. The summed values are // Put the data into the destination image. The summed values are
// of double data type and are rounded here for accuracy // of double data type and are rounded here for accuracy
dst_data[0] = (unsigned char)(sum_r + 0.5);
dst_data[1] = (unsigned char)(sum_g + 0.5);
dst_data[2] = (unsigned char)(sum_b + 0.5);
dst_data += 3;
if ( src_alpha ) if ( src_alpha )
{
if ( sum_a )
{
dst_data[0] = (unsigned char)(sum_r / sum_a + 0.5);
dst_data[1] = (unsigned char)(sum_g / sum_a + 0.5);
dst_data[2] = (unsigned char)(sum_b / sum_a + 0.5);
}
else
{
dst_data[0] = 0;
dst_data[1] = 0;
dst_data[2] = 0;
}
*dst_alpha++ = (unsigned char)sum_a; *dst_alpha++ = (unsigned char)sum_a;
}
else
{
dst_data[0] = (unsigned char)(sum_r + 0.5);
dst_data[1] = (unsigned char)(sum_g + 0.5);
dst_data[2] = (unsigned char)(sum_b + 0.5);
}
dst_data += 3;
} }
} }