[scribus] Images/PDF sizes/Cropping etc

[Owen]

Following some discussion about Scribus document sizes, cropping etc, I
wrote what is below and it may be of some value.

Note that todays camera are in the 12 megapixel range, it is absolutely
essential that these be reduced to just what is need otherwise you will
need a Google sized storage system to store your pdfs as well as a
gigabit connection to download them.

I suggest you just experiment. 

Owen


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To minimize the output size of a pdf, it is probably wise to resize
your images, depending on the intended use. 

It is suggested that you experiment with with your image and pdf
output sizes. For example, a B&W image can be around one tenth the size
of a color image. 

Note, figures below are based on a color jpeg. YMMV with pngs, tiffs or
whatever. Just experiment.

What is the size of your image
------------------------------

a. Most programs allow you to right click to show properties. You will
find somewhere an entry like;

	Width: 2448 pixels
	Height: 1836 pixels

b. Open the image in gimp, look at the top of the GUI, it will show the
size.

c. There are other tools.


How do you want to display your image
-------------------------------------

There are two basic presentation modes;

a. On paper, 150 - 300 DPI is a normal range. Your home printer
can probably cope with 300 DPI 

b. On the web, here dpi varies from say 75 to 100.

Both options are available in Scribus via the PDF export dialog
(Color->Output intended for)


The Hard Part - Maths
---------------------

DPI stands for Dots Per Inch, so we will work in inches.

a. Formula 1. Pixels ÷ DPI = Inches

Thus an image 2048 pixels wide by 1536 high will allow an image to be
place in a Scribus document that at 300 dpi, will be 6.83 x 5.12 inches
in size (173 x 130 mm)

Exporting such a color image as a pdf in a Scribus document may result
in a file size of over 8 mb (1 mb in B&W)

In Scribus, you can adjust the image frame size, making the frame
smaller will not result in a smaller pdf.

b. Formula 2. Inches X DPI = Pixels

Say you wanted the image frame to be 2.28 x 1.7 inches (1/3 size).

Then the image size only needs to be;

2.28 x 300 pixels wide, and 1.7 x 300 pixels high. (Color = 950 KBytes)


How do I get a smaller PDF
--------------------------

To get a smaller pdf, insert an image that does not exceed the minimum
requirements for production. Thus a color image re-scaled to fit in a
2.28 x 1.7 inch frame at 300 dpi will produce a pdf that is 950 Kbytes
(9% of the original size) 

What if I want to present for the WEB
-------------------------------------

Here, all is needed is to re-calculate according to the formula above,
using 75 - 100 DPI.

Thus to produce a pdf suitable for viewing on the web at 100 DPI:

eg;  2.28 x 100 pixels wide and 1.7 x 100 pixels high

That will produce a pdf that 27Kbytes, 0.34% the original 8mb.

At 75 dpi, it is even smaller


How do I resize an image
------------------------

There are probably many tools available, but using gimp is probably the
best as it is often the default graphics application for Scribus. You
can do it directly in gimp, Image->Scale image, setting the width and
height as well as the resolution.

In Scribus, Right click on your image in the image frame and select
"Edit image". That will bring up the default graphics application.

You need to save the resized image, use a different file name, and then
do the Get (the new)Image bit again.