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Subject [Bug 121233] Lanczos3 resampling for Bitmaps
Date Fri, 19 Oct 2012 09:59:05 GMT

Andre <> changed:

           What    |Removed                     |Added
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--- Comment #8 from Andre <> ---
@Toma┼ż: Thanks for improving the bitmap resampling.
At first I wondered why you reimplemented the convolution but then I looked at
Bitmap::ImplConvolute3 in vcl/source/gdi/bitmap4.cxx an saw why.  Maybe we can
replace it with your code.

Two remarks:

1. At about line 25 of your patch there is a line
+        else if( BMP_SCALE_LANCZOS == nScaleFlag )
that exists twice (the copy is two lines down).

Remove the first to activate the Lanczos resampling.

2. In ImplScaleConvolution you are using an separable kernel.  If I understand
that method correctly then ImplConvolutionPass is used to do a horizontal
application of the two one-dimensional kernels.  For this to work the image has
to be transposed twice.  Either I am not understanding all this correctly or I
fail to see where the transposition takes places.  Can you explain what I am

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