How to make brown pages black and white

[Sivori]

I manage to make it black & white with Irfanview and paint with https://imslp.org/wiki/IMSLP:Image_Conversion
When you use Width and Heigth 360 in Irfanview it becomes black, so I use 300 or 250 or 200 to get it black and white. The b&w tiff-files I made horizontal with photo gallery and copy it in a A4 jpg-mold of the ricght size. There I make it horizontal with photo gallery. Later I despickle it with paint. With https://jpg2pdf.com/nl/ you can make the jpgs to 1 pdf.

[coulonnus]

I had a look at your last version of https://imslp.org/wiki/Violin_Concertin ... ff,_Leo%29 It is not monochrome but grayscale, providing a much bigger file. A decent pdf should not be bigger than about 100 kB/page.

[Sivori]

Ok, but how do you convert a big grayscale pdf to a smaller monochrome pdf with Adobe Acrobat Reader or otherwise?

[coulonnus]

I uploaded a monochrome version on this work page. Compare the sizes. I split the pdf into single pdf pages with pdftk. I converted each page to jpg with imagemagick with:

FOR /L %%A IN (%2,1,%3) DO (magick -density 200 p%%A.pdf p%%A.jpg)

density 200 makes the resolution of the jpg pages neither better nor worse than that of the original pdf. Then I re-sampled all pages to 600 dpi with
FOR /L %%A IN (%1,1,%2) DO (convert -resize 300%% -filter triangle p%%A.jpg p%%A.jpg)

Then I cropped the margins with irfanview and used procedure 5 in https://imslp.org/wiki/IMSLP_talk:Scanning_music_scores with a 60 % threshold.

[Sivori]

That is too difficult for me. With https://imslp.org/wiki/IMSLP:Image_Conversion and https://pdftoimage.com/nl/ and easy available programs like Irfanview, Paint and photo gallery I manage to get it black and white with too much Mb. Perhaps you can make a clear and slow movie for dummies?

[coulonnus]

Let us proceed by steps. Assuming the pdf is named concerto94.pdf, type pdftk concerto94.pdf cat 2 output p2.pdf. The size of the pdf should be
455.292k.

Then type magick p2.pdf -density 200 p2.jpg. The size of the jpg should be 945.789k.