How to convert vectors within pdf into non-vector (e.g. jpg) to reduce file size?

Report · Dec 15, 2020

Hi guys,

I create a lot of notes on my iPad in OneNote (using the pen). When I export the file, I get quite a large pdf, that may contain pictures (if I inserted screenshots) but mostly vectors of my writing. Those make the pdf-file size quite large.

Now I would be fine loosing some quality if the Acrobat Pro would dismissed the vectors and created jpegs of them instead, which are then compiled into a pdf. I guess that should create a much smaller file size.

However, I cannot find any function that would allow me that. I've tried using the printer and fumbled with the setting therein (reducing & recalculating "pictures") but I came to understand that within that function, vectors are excluded. They are not seen as pictures and therefore not recalculated into jpegs.

Any hints on how to do that?

Thanks and best regards!

I'm using Adobe Acrobat Pro XI

Report · Dec 15, 2020

Piece of information for you: a vector of a line is smaller than a bitmapped version of the same line.

A vector is composed of three pieces of information: the starting point, the ending point, and the width of the line. Oh let me add one more data point: the color of the line.

A bitmapped version of that line means that for every pixel involved, there is data for that pixel (including any anti-aliased pixels added in to smooth the line out) and their color.

So line for line, a vector is smaller in storage size.

As a side comparison, if you scan a page of text and save as a TIF image, at 300 ppi, the TIF version is about 8 MB. The JPG version is about 2.5MB-4.5 MP (depending on density of text and how much compression is going on). If you OCR the document and convert the bitmapped text to actual (vector) text, the document will be about 90-140 kilobytes.

Oh, one other aspect of vector images versus bitmapped images and storage size: if you double the size of a bitmapped image, the storage size goes up fourfold. If you double the size of a vector image, the storage size goes up a negligible amount (a couple of kb at best).

Having never used OneNote, I cannot speak with any authority on the size of these documents nor on the size of the vectors involved that they create. I can however, talk about vectors versus bitmapped imagery and storage size issues.

Report · Dec 15, 2020

Hi Gary,

Thanks a lot for your answer! I'd love to buy in into every aspect of your reply. However, I just experimented with one note as an example:

PDF with vectors: 2.74MB

4 Screenshots of the same document with a few overlaps, so with more data: 1.45MB (-45% of file size, well readible quality).

I guess what usually makes vectors small is their easily calculatable nature. When it is handwriting, I guess they become larger datasets quite easily.

Best regards,

Tobias

Report · Dec 15, 2020

Hi Tobias,

As I just read your comment I realized one issue with handwriting that I hadn't considered as I was writing: more points! For every extra point in a vector drawing the size of the document does go up.

One of the features in Illustrator when taking a photo and converting it into a vector is to reduce the number of points along any given line. By simplifying the number of points, the size does go down. During original creation, more points are added because it's faster. For simplification, the bezier handles are adjusted to accompish the same shape and can then remove unnecessary point but that takes time.

I apologise for not thinking of that dynamic before.

[That notwithstanding, what would be better than converting it into a jpg is to have the number of points simplified. But then again, isn't this something that Microsoft needs to consider as OneStep is their product, no? (sounds like time for finger pointing time ;>)]

By the way, if you meant to include some screenshots, they did not make it into your message. If you want to include them now, please use the "Insert Photos" tool/icon in the top of the writing box, it's the 3rd one to the left of the "HTML" icon on the right hand side.]

One last thought/question: What kind of "Save" options are available in OneNote? That is, can you save it as a JPG or PNG from within OneNote? If so, wouldn't that do it for you? [Comment: the image quality of PNG documents is vastly superior to JPGs becuase it's not a lossy format and therefore doesn't have the degredation issues that JPG has. (If it does, select PNG-8, you do not need PNG-24. You'll get a smaller documents size and since you do not have an image with millions of colors, you do not need the -24.)

Good luck!