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Say I create an image of 100x100 pixels in an area of 1x1 inch in my article. Lets say, when viewing the pdf at 100% magnification on my monitor, this 1x1 inch area covers 50x50 screen pixels.

If I were to digitally zoom so that the image would cover 100x100 pixels on my monitor, would it equal the original image? Or are the new pixels being interpolated by the pdf software?

I guess I'm wondering how the image is saved in the pdf, as a scaled down version or the full version? This page implies that graphics just get higher dpi mapping: Can pdflatex (or any tex package) automatically rescale included images which have been reduced in size? It seems all data is saved...so zooming could work?

would using \pdfimageresolution overwrite the dpi values? If it does overwrite, are the images scaled to retain their size in the document?

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As a side note, many modern graphic packages creates their images in scalable (non-rasterized) format. When this is done, the perfect image quality is conserved no matter what the zoom. – Steven B. Segletes Apr 13 '13 at 14:18
Welcome to TeX.sx! The magnifications are only a approximation (the viewer would need to know the pixel dimensions and their distances. To answer your question: No, there aren't any pixels interpolated (without special settings), at least with the document I just examined. If you insert your graphics with the graphicx package (don't you?), you can use the option interpolate which will activate the interpolate feature of the viewer. – Qrrbrbirlbel Apr 13 '13 at 14:22
As far as I know images are included in their original form by pdftex. If you get exactly the original 100x100px after zooming depends on your PDF viewer and other settings I guess. Usually PDFs are not displayed by pixels but by print size and therefore it depends on the DPI settings used etc. – Martin Scharrer Apr 13 '13 at 14:29
Thanks guys, maybe not the best first question. I guess the pdf viewer plays a role too, as theres a smart(change dpi) and a dumb(screen pixel interpolating) way to zoom PDFs. – Jayvl Apr 14 '13 at 12:36

The PDF format is a vector format (what is represented in a PDF is lines, not pixels). So you can blow them up all you want.

But parts of the PDF can be represented in raster format (pixels), notably images imported from some other format (GIF, PNG, JPG are raster formats; it's just too bad there aren't programs smart enough to interpolate smoothly...). If you scan a page and save in PDF, it is represented ad a raster.

If you take a 100x100 pixels, you have a raster image.

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@MartinSchröder That is what I said? – vonbrand Apr 13 '13 at 17:50

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