blur and sharpen

[jsteinkamp]

Summary of the bug:
Smartblur and unsharp create a corrupted tif file.
In addition, Smartblur and unsharp lose the alpha layer for PNG format files.

How to reproduce:
TIF with alpha channel and without alpha channel
ffmpeg -y -i file.tif -vf smartblur file_sharper.tif
ffmpeg -y -i file.tif -vf unsharp file_sharper.tif

PNG with alpha layer
ffmpeg -y -i file.png -vf smartblur file_sharper.png
ffmpeg -y -i file.png -vf unsharp file_sharper.png

ffmpeg version N-104454-gd92fdc7144-20211030

built on built with gcc 10-win32 (GCC) 20210610

configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --enable-shared --disable-static --disable-w32threads --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --enable-libvmaf --enable-vulkan --disable-libxcb --disable-xlib --enable-amf --enable-libaom --enable-avisynth --enable-libdav1d --enable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-frei0r --enable-libglslang --enable-libgme --enable-libass --enable-libbluray --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --enable-libmfx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --disable-libdrm --disable-vaapi --enable-libvidstab --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --enable-libzvbi --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags= --extra-libs=-lgomp --extra-version=20211030
libavutil 57. 7.100 / 57. 7.100
libavcodec 59. 12.100 / 59. 12.100
libavformat 59. 8.100 / 59. 8.100
libavdevice 59. 0.101 / 59. 0.101
libavfilter 8. 16.100 / 8. 16.100
libswscale 6. 1.100 / 6. 1.100
libswresample 4. 0.100 / 4. 0.100
libpostproc 56. 0.100 / 56. 0.100

Input #0, png_pipe, from 'file.png':

Duration: N/A, bitrate: N/A
Stream #0:0: Video: png, rgba(pc), 128x128 [SAR 2835:2835 DAR 1:1], 25 fps, 25 tbr, 25 tbn

Stream mapping:

Stream #0:0 -> #0:0 (png (native) -> png (native))

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.