vcl/source/bitmap/BitmapScaleSuperFilter.cxx | 11 +++++++++++
1 file changed, 11 insertions(+)
New commits:
commit 050c51d55b77a5f8a66d1da6a74d741d81510b21
Author: Luboš Luňák <l.lu...@collabora.com>
AuthorDate: Fri Dec 3 13:48:12 2021 +0100
Commit: Luboš Luňák <l.lu...@collabora.com>
CommitDate: Sat Dec 4 16:49:23 2021 +0100
resurrect description of the "super" scaling algorithm
Commit 53d51dbee6d4037c4cfc3fa743de8dac76da48c6 described it
only in the commit message, but that's hard to find if I want to
know _now_ what the thing does.
Change-Id: I012ead2aa9d81ce1287da3a32e43a038cd9ba18d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/126316
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lu...@collabora.com>
diff --git a/vcl/source/bitmap/BitmapScaleSuperFilter.cxx
b/vcl/source/bitmap/BitmapScaleSuperFilter.cxx
index bc7f3a8361f4..59ed78c8d6f3 100644
--- a/vcl/source/bitmap/BitmapScaleSuperFilter.cxx
+++ b/vcl/source/bitmap/BitmapScaleSuperFilter.cxx
@@ -29,6 +29,17 @@
#include <svdata.hxx>
#include <sal/log.hxx>
+/*
+A scaling algorithm that uses bilinear if not downscaling too much,
+and averaging otherwise (bilinear would produce poor results for big
downscaling).
+
+By default the combination of two filters is used: bilinear and averaging
algorithm.
+Bilinear filtering is used for bitmap enlarging and shrinking till factor 0.6.
Below
+this bilinear gives bad results because of limited sampling. For such cases
averaging
+is used which is a simple algorithm for shrinking. In averaging the algorithm
+calculates the average of samples which result is the new pixel.
+*/
+
namespace {
constexpr int MAP_PRECISION = 7;
