[FM Discuss] Optimizing images for printing

[Daniel James]

Hi Elisa,

>     trouble with pictures for web is that they are 2 small for print
>     purpose.

That depends on the size they are printed. For example a 600 pixel wide
PNG is fine in theory for laser print as long as it is not printed at
more than 3 inches (76mm) across, which makes 200 pixels per inch (ppi).
That printed size of 76mm is OK for detail screenshots but not so good
if you're trying to show a whole desktop.

> Furthemore when the web view host image larger than 650 px of width
> (because the content is limited in 650px), i think it would be useful if
> the image could be see at his original size.

Right, what Booki needs to do is create a 600 or 650 pixel wide
thumbnail from any uploaded image that is wider than this, and use the
thumbnail in the HTML layout with a click through link to the original,
but just the original in the PDF export.

> We can imagine asking them to upload
> the best big image they could and after booki transform it for web and
> printing view (if possible, if not => message).

Given the high resolution of monitors and cameras these days, it could
be a waste of disk space to upload the largest image possible. It's
better if the authors prepare the images for the intended use.

So if your book is US TRADE size you only have about 115mm printable
width per page. That means a 1920 pixel wide image would be printed at
over 425 ppi, which is more than we need for print on demand presses.
For the Airtime book we printed screenshots at only 135ppi, and in
general they looked fine.

A bigger issue is that fonts in screenshots are not vectors, so they
don't look as crisp as fonts in the body text when printed. (Desktop
monitors are around 100ppi, depending on the model). This cannot be
addressed with higher resolutions because one pixel on the desktop is
one pixel in the screenshot. Print at a higher resolution, and the fonts
in the screenshot will be too small to read (e.g. at 300 ppi the printed
image will be around 1/3 of real life size).

Also, if the program you are screenshotting has a dark GUI, it won't
print well on cheap uncoated paper because of the increased absorption
of ink. Again, this won't improve with higher resolution - your only
options are to use a light GUI skin whenever this is available, or pay
extra for coated stock (china clay or chalk impregnated paper).

Cheers!

Daniel