How do pixels in .bmp or other bitmapped graphics inserted into MS Word documents get through the process of being printed to .PDFs (selecting PDF-XChange 3.0 as the printer), and what determines whether they remain clearly distinct picture elements when viewing the .pdf later?
I use Microsoft Word 2003 to create technical reports, usually with pictures inserted from .bmp files. Most often I “print” from Word and select “PDF-XChange” as the printer. This is some trick that generates a .pdf file rather than hardcopy. It was set up by the IT folks, who I guess bought this pseudo-printer utility and integrated it with our corporate laptop setups.
The problem is that I am pretty sure sometimes some kind of resampling happens such that the graphics can’t be viewed (using a .pdf reader such as Adobe) with full resolution of the original pixels, even if I keep zooming in. I want to be able to use graphics whose fine detail can be recovered by people reading the .pdf, and instead the pixels run together into a blur.
But I just did some experiments to try to figure this out. I used Paint to create .bmp files of various sizes that are white and black pixel checkerboards at the finest scale. I then put all these different size graphics into a Word document, sometimes by just inserting them, and sometimes grabbing the corners and resizing after inserting them. Then I “printed” to a .pdf file and examined it. In all cases, I can keep blowing up the view magnification in Adobe Reader until I see a clean, clear, perfect checkerboard. I am not reproducing the blurring effect.
So, I wish I knew more about this. What should I expect to happen, and why?
I don’t know about Microsoft Word, but when generating PDFs from Adobe products, one is offered the choice of down-sampling bitmaps if they are greater than a certain resolution. This choice is usually made if the target is “web” as opposed to “print.” Whoever made your workflow may have hard-coded in the downsample step - check with them.
The way these fake PDF printers work is that they pretend to be, well, printers. The way most printers work is that, in order to print the image at a specific size, it has to have a certain number of pixels, as set by the PPI (pixels per inch) setting. So it thinks it has to resize the image to fit. The only way to get around this is to set the PPI to be the same as in the image you are printing.
I do not understand why your checkerboard patterns are coming out all right, unless you are not using large enough images. For example, if you are printing at 100PPI, a one inch image should be exactly 100 pixels tall and 100 pixels wide. Any other size should cause the image to be resampled.
Now, it’s possible the PDF printer is set up in such a way that it gets around this somehow, essentially telling Word that it will handle the resampling itself, rather than making Word do all the work. If that’s the case, though, I can’t understand why the images would ever be resampled.
Still, I do have a suggested solution: always use images of the same PPI as your PDF printer. If you need higher resolution images, then I would see if you could change the PPI setting in the printer properties before you print.
BTW, PPI is sometimes erroneously called DPI, which means dots per inch. This is technically a different concept when it comes to printing, as a pixel can be made up of multiple dots, as pixels can be nearly any color, but dots are limited to the colors of the ink in the printer. But it doesn’t stop many graphics programs from using the wrong term.