Image preparation

Functionality

Image preparation is typically performed by the layout person.

The author should supply images in a “raw” format, that is without any applied image manipulation such as cropping or sharpening.

If images are supplied as paper copies, they should first be scanned. “Graphic art”, ie logotypes, should be traced in the vector graphics software and transformed (traced) into vector art.

Bitmap image editing

The following actions are typically applied to an image before including it in the layout:

  1. Cropping.
  2. Setting resolution (often 300 dpi for offset printing).
  3. Adjusting size.
  4. Adjusting levels (setting black and white point).
  5. Adjusting curves and adjusting brightness and contrast.
  6. Adjusting the color balance and adjust hue/saturation.
  7. Performing touch up: removing unwanted details.
  8. Masking.
  9. Sharpening.
  10. Separation (if this is not handled by the page layout software, ie when creating the print-ready PDF).

Good selection tools and layer capabilities helps the workflow.

Here are some suggested start values for the Unsharp mask filter in GIMP:

  • Radius: 1,2
  • Amount: 0,5
  • Threshold: 8

Vector image editing

It's useful to open the vector document in a vector graphics application and do the following:

  • Check and if necessary (and possible) adjust the color space.
  • Clean up: remove stray points and lines.
  • Check that no white frames (areas) are left that look like they are transparent (but are not).
  • Perform simplifications to increase performance.

Software

See Step 1: Manuscript preparation - Software.

File format

Bitmap file format

Desirable qualities of an image file format is that it:

  • uses non-destructive compression (or is non-compressed)
  • handles clipping paths or transparency (or both)
  • handles different color spaces
  • preferably handles large color depths; more than 8 bits per color (channel)

Work is currently being done on the Open Raster format. The Scribus documentation team recommends TIFF and PNG.

Vector file format

For vector graphics there is an open standard format, SVG. Color space in SVG is always sRGB.

Tutorials