Notes on importing issues with Scribus
Although Scribus imports most common DTP image formats like TIFF and EPS, over time one of the more difficult tasks in DTP is getting stuff from different resources into your layout. Unlike some other DTP programs where printing can be finicky, Scribus print and PDF export has always been very reliable, and with correctly prepared images and files, the output from Scribus will be of excellent quality.
One key to this is using the right format for the right type of image. Whenever possible, import your images as vector (e.g. SVG, EPS or AI). Another key to successful layout is fonts. When you are working with high-end DTP tools like Scribus, font quality matters. In professional DTP, it matters a lot. Probably the number one reason PostScript output fails, whether to a printer or PDF export, is a dodgy or corrupted font.
TIFF, JPEG, GIF, PNG what is the difference?
If it looks good on screen it will look good on paper
This is, unfortunately, an error that may cost real money. One of the most common beginner mistakes is to assume a nice looking JPEG from a website will print nicely on paper. Most websites use JPEGs, GIFs or - still less commonly - PNGs. JPEGs, by their design, use lossy compression. In the process of compressing a JPEG, data is discarded and permanently lost. Moreover, there is a type of JPEG called progressive which is pure poison in a PostScript workflow. A progressive JPEG is the type that partially displays as it is downloading in a web browser. Avoid these at all costs. Scribus will not load, nor export progressive jpegs. Also remember that most web page graphics have a resolution of 72-96 DPI, which is far too low for a print workflow. Scribus can generate PDFs with 4000 dpi, but for most purposes 300 dpi is a reasonable resolution.
Another issue with JPEG files is that every time you open and edit them in an image editing program you will lose image data. So if you need to edit a JPEG file, save it in another format, like TIFF, before you start applying any changes.
Scribus supports a few other formats, but you should avoid them for serious print jobs. These are:
- GIF: The GIF format has been created for the early days of the world wide web. It uses compression and only permits a limited number of 256 colors. While it's possible to load a GIF image into an image frame, the format really has no place in professional page layout. This can get really ugly when you try to import a so-called "Animated GIF". These GIFs work like a flip-book and are comprised of several images that will be subsequently displayed by a broswer. They have no place in professional printing.
- XPM: This is an old bitmap format used for icons in the X Window System. Like GIF, it only supports up to 256 colors.
- BMP: A bitmap format used by Windows and OS/2 for graphical user faces. Unlike GIF or XPM it can contain up to 32 bit per pixel and supports transparency. Due to its simplicity, the BMP format is wide-spread and can be read/written by most image editors. Unfortunately, the lack of a compression algorithm leads to comparatively huge file sizes, and BMP data may cause problems with commercial RIPs (Raster Image Processors).
- If you are preparing a PDF or PostScript file for commercial printing, convert any of these file types to a more reliable format, like TIFF or PNG.
For high-level PostScript printing there are three kinds of file formats that work well for images like photos and anything that is made up of pixels and have been time tested: TIFF, tif and Tiff.
No matter which way you spell it, the Tagged Image File Format is the file format for bitmap images.
- It is a lossless format. The compression scheme does not reduce quality.
- For your purpose of working with Scribus, the GIMP or Krita do a fine job of exporting or saving to TIFF.
- It handles ICC profiles without problems. You can "tag" it with the LittleCMS utility
tifficcor embed an ICC profile in many bitmap editors.
- It supports CMYK colors better than almost any other bitmap format.
- Every high-end DTP application can support them, including Scribus.
- TIFF files, if they are prepared properly in an image editor are extremely reliable when printed commercially. Rarely do PostScript devices have problems with them.
There are more than fifty different flavors of TIFF. Not every image editor saves them with the same fidelity to the standards. GIMP, through its use of libtiff, shared with Scribus, does a fine job of supporting TIFFs. One way to work with files from GIMP is to save the original file in the native GIMP XCF format and then, once edited to your satisfaction, export as a TIFF or, with screen shots meant for the web, PNG.
The latter, PNG, is an exception to the aforementioned rule, especially for application screenshots. PNG has a lot of advanced features, like ICC color support and real alpha transparency, which are often not supported well by some applications (a certain leading browser comes to mind). PNG also compresses very well. The only time JPEG may be preferrable over PNG is for photos with high dynamic range, mostly for reasons of size on a web page. For creating PDFs with screenshots, PNG is superb and will print well, as long as you do not make any scaling adjustments which reduce the image size. So if you have a screenshot which is typically at 72-96dpi, but you need to shrink it, do so by scaling the image in the GIMP or within Scribus. Whenever you are scaling screenshots, disable re-sampling in any image editor. With screenshots you should never reduce the number of pixels or you will lose sharpness quickly.
If it looks bad on screen, it will print terribly
This not necessarily true. EPS (Encapsulated PostScript) files need not have a screen preview at all. EPS files are really a special subset of PostScript instructions. They sometimes look just plain awful on screen if they have a TIFF or PICT preview embedded or are just a simple gray box. EPS files have two important virtues: They deliver excellent results on both high-resolution printers and when creating PDFs. EPS files can be resolution independent and are the only file you can (sometimes) safely scale larger than 100% than its native size without degrading image sharpness.
The major issue you might find with EPS files is that while a lot of applications can generate EPS files, not all do so with the same fidelity to high-quality printing, nor do all apps follow the EPS specs properly. One way to test an EPS for use with Scribus, is to open the EPS in <a href="toolbox6.html">GSview</a> and look in the message box, by pressing Shift M. This will show the output messages from Ghostscript. Ghostscript is correctly quite fussy about EPS files. So, if you are trying to import EPS files that do not work properly in Scribus and GSview/Ghostscript is spitting lots of error messages, try using a different application to generate them.
One reason for the ubiquity of EPS files in DTP is the existence of another DTP application which historically had poor support for TIFF and other bitmap image files, but does have good support for EPS import. So, many DTP users habitually create EPS files from bitmap images from Photoshop or others. Unfortunately, this can have the side effect of receiving image files which may need adjustment, which is impossible without the original image file. EPS is also great for receiving vector artwork like maps, mixed with text. The caveat is that the fonts should be correctly embedded in the EPS to print properly from Scribus.
When importing an EPS, Scribus generates a 72 dpi PNG preview of the EPS, so do not be concerned if it does not look sharp right away. Printing or exporting a PDF will generate the high resolution image in the file.
If you're still skeptical about the difference between a vector and a bitmap image file, here is an example that you can see for yourself. Go to: http://www.isc.tamu.edu/~lewing/linux, get the linked PostScript, which is an EPS version of Tux and then right click and download one of the GIFs. They are about the same in file size. Now create a new document in Scribus with 2 regular size pages. Place the GIF on one page and then the EPS file on another and export a PDF at 600+dpi. Now open the PDF in Adobe Reader. Zoom in 200-400 %. Now you see the difference ...
Why the difference? Scribus creates and Acrobat Reader renders something called PostScript operators - another fancy name for using math in drawing curves on screen and when printed. A GIF or JPEG file is just a bunch of pixels, literally dots to create the image.
A vector format for the future
With the addition of SVG import users have one more excellent way of importing images and artwork. SVG is an abbreviation of "Scalable Vector Graphics", an open specification, which is developed by the World Wide Web Consortium. Scalable means that you can in theory enlarge the the graphic to the size of the side of a house and it would retain its sharpness. Vector is how it does it, vectors meaning the shapes are drawn by mathematical commands instead of pixels. The leading Open Source vector drawing program, Inkscape, uses SVG as its native file format, which is yet another reason for its importance to Scribus users.
Other vector formats
Over time, import filters for other vector formats have been added, and there are many more to follow. See Importing Vector Drawings for more details.
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