diff options
| author | Luboš Luňák <l.lunak@collabora.com> | 2021-12-03 13:48:12 +0100 |
|---|---|---|
| committer | Luboš Luňák <l.lunak@collabora.com> | 2021-12-04 16:49:23 +0100 |
| commit | 050c51d55b77a5f8a66d1da6a74d741d81510b21 (patch) | |
| tree | 58f3ebf02326ae64dfa4c7f7ce88afa24dc7de4d /vcl/source/bitmap | |
| parent | fb37997ece889d9a90bb5de600fcb763d339734c (diff) | |
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.lunak@collabora.com>
Diffstat (limited to 'vcl/source/bitmap')
| -rw-r--r-- | vcl/source/bitmap/BitmapScaleSuperFilter.cxx | 11 |
1 files changed, 11 insertions, 0 deletions
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; |