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I'm using Bullzip PDF Printer. First I printed a webpage to file using 300 DPI and resolution 2479x3508 resolution.

Second, I took a screenshot with Print+F11, saved and opened with Paint.NET and set DPI to 300.

The quality of both is different. The first image, with almost max zoom, displays the image in detail, while the second, with even a little zoom, displays pixels/squares.

Can print-geeks explain to me why that is? In both cases I made a screenshot, but why does the picture look different when zoomed?

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3 Answers 3

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In the first instance, you didn't take a screenshot. You ran a piece of software that "rendered" (or drew) the web page on to a virtual screen with the dimensions 2479x3508 pixels.

In the second instance you did take a screenshot of what had already been drawn to your screen at 800x758 pixels.

This means that your screenshot is actually ~4x smaller along it's dimensions. So if you were to print out both at 300 dpi, the former would come out at 8.26" wide and the latter at 2.6" wide.

To get the prints the same physical size the latter's pixels are ~16x larger and hence will look blocky when compared to the former's pixels. You simply have more information in the first print.

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Printing a webpage to a file is not the same thing as taking a screenshot.

When you take a screenshot, you are not taking a copy of the web page, you are taking a copy of the screen. You cannot see detail when zoomed in because there was no more detail on the screen when you took the screenshot.

When you print a webpage to a PDF file, it sends the drawing commands to the PDF file. When you zoom in, it is re-drawn at a larger size. That is why you can see more detail.

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The reason is likely that your screen resolution is not 2479x3508 (which is probably the resolution if the original image from the webpage), and is lower than that value (i.e. 1024x768, 1600x1200 etc.). Therefore, you have less information in the screenshot.

The DPI is only a correspondence between the size in pixels and the size it would have when printed on paper, i.e. it's a density of information description. For instance, your 2479x3508 image would be printed, at 300DPI, with a size of 8.26 in x 11.69 in (divide both numbers by 300).

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So are you saying the result would be identical had the screen resolution been 2479x3508? –  Pacerier May 17 '12 at 22:16
    
Most likely, yes. –  Karolos May 21 '12 at 19:38
    
What factors would have made it different despite a screen resol of 2479x3508? –  Pacerier May 22 '12 at 6:26
    
Well, for example, given it's a webpage, the browser could have it zoomed in, which could not be reflected by the PDF printer, depending on how it operated. It would however be zoomed in in the screenshot, event at the resolution you mention. –  Karolos May 22 '12 at 7:34

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