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I have a JPEG of 440KB. When I open it in Preview on Mountain Lion and save it as a PDF the PDF is 2.8MB. The PDF version is 1.4 and the PDF producer is Mac OS X 10.8.2 Quartz PDFContext

Why has the size increased so much? And how can I save the file as PDF and keep more or less the same size?

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up vote 2 down vote accepted

When you preview the JPEG it will have to be decoded from it current compressed (JPEG) format to a bitmap. (This is always the case when you view a picture).

When you create the PDF Quartz is not inserting the JPEG file from disk. Instead it is creating a PDF with a newly encode JPEG, with different settings. If those settings default to keeping a higher picture quality * then the resulting file will be larger.

* Or rather preventing quality loss

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I've checked this, and indeed the default behaviour of PDF Quartz is to save images in an uncompressed format. This can be changed by applying a custom quartz filter on the PDF. Thank you for your help. – Saaru Lindestøkke Feb 1 '13 at 17:07
In that case I am slightly wrong. PDFs allow two kinds of images. One type is JPG, the other type is an uncompressed format which technically is not in JFIF/JPEG format. – Hennes Feb 1 '13 at 18:11

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