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• avfilter/vf_ocr : add white space to whitelist

  18 mars 2021, par Dominic Mayers

  avfilter/vf_ocr : add white space to whitelist
  Fixes #9151. The current version of libavfilter/vf_ocr.c does not have white
  
  space in the default whitelist. But it is recommanded to include white
  
  space. See https://github.com/tesseract-ocr/tesseract/issues/2923
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] libavfilter/vf_ocr.c

• ffmpeg convert white color to alpha

  11 janvier 2021, par tony

  Hello i took a picture with my camera :a drawing of a square frame on a white paper ; i'm trying to convert the white to transparent and keep the black color frame.

  


  So i started making 1 palette with only 2 colors to make the colors uniform and 1 palette to add the transparency

  


  ffmpeg -f lavfi -i "color=color=white:100x100" -f lavfi -i "color=color=black:100x100" -filter_complex "[0][1]hstack" -frames:v 1 blackwhite.png`
ffmpeg -i blackwhite.png -filter_complex "[0]split[a][b];[a]palettegen[pal1];[b]palettegen=reserve_transparent=on:transparency_color=white[pal2]" -map [pal1] palette1.png -map [pal2] palette2.png


  


  then i mapped the image png of the frame to convert the white to transparent and overlayed the result to a red background

  


  ffmpeg -i image.png -i palette1.png -i palette2.png -i background.png -filter_complex "[0:v][1:v]paletteuse=dither=bayer[a],[a]split[a1][a2];[a1][2:v]paletteuse=alpha_threshold=128[c];[3:v][c]overlay[d]" -map [a2] -c:v png out.png -map [d] -c:v png out1.png


  


  the png mapped to the first palette (as a test) comes as it should be, pure black and white,the second comes with no transparency at all and covers the background
what am i doing wrong ?

  


• ffmpeg convert white background to transparent

  7 janvier 2021, par tony

  Hello i took a picture of a framed sheet with my camera and i'm trying to convert the white background to transparent without using the colorkey filter. It is meant to be for a video using a number of frames overlayed to a static background but i started with only one png to see if it works.

  


  So i started making 1 palette with only 2 colors with -f lavfi (black and white) and 1 palette to add the transparency

  


  ffmpeg -i blackwhite.png -filter_complex "[0:v]split[a][b];[a]palettegen=max_colors=4[out1];\
                            [b]palettegen=max_colors=4:reserve_transparent=on:\
                            transparency_color=#FFFFFF[out2]" \
    -c:v png \
    -map [out1] paletteNormal.png \
    -map [out2] paletteTransparent.png 


  


  then i mapped the png that i want to convert to the first palette to make uniform colors and then to the second to add the transparency and i overlayed the result to a background image that should be red

  


  ffmpeg -i image.png -i paletteNormal.png -i paletteTransparent.png -i background.png \
     -filter_complex "[0:v][1:v]paletteuse=dither=bayer[a],\
     [a]split[a1][a2]; \
     [a1][2:v]paletteuse=alpha_threshold=128[c];[3:v][c]overlay[d]" \
    -map [a2] -c:v png out.png \
    -map [d] -c:v png out1.png


  


  the png mapped to the first palette comes as it should be, pure black and white
the second comes with no transparency at all and covers the background
i tried different combinations like to make the second palette of 255colors..... nothing

  


  what am i doing wrong ? i know it can be done
i went to this site and i made an alpha channel in 5 seconds with a lot of grief and rage.linkOfPain

  


  p.s for a video from png frames what codec should i use ?