7.4

Guidelines for Optimizing Images
Images increase the execution time of a document and in the case of image resources, also increase the file size of a doc-
ument. Tuning images to the execution environment of the document and the image quality required in the output, keeps doc-
ument file size and execution time to a minimum.
This section provides suggestions for reducing the file size of images and minimizing the amount of runtime processing they
require, without compromising the required image quality. These are general guidelines. In any real-world situation, there are
often trade-offs to make among image quality, image file size and document execution speed.
l Image Formats:Unless displaying complex images such as photos, landscapes or very complex logos, vector-based
images are normally faster and offer better quality on your printer than bitmap (raster)images.
l Image Resolution: Always set bitmap (raster)images to Constant Resolution. If the image appears to be too large
for your page, it means its resolution is too high and it should be resized to be smaller and fit within the page. Ahigher
resolution image will not printer better on your printer - it is limited by its own resolution (normally 600DPI) and the
technology used to print colors and greyscale image.
l Scanline Orientation:Always use bitmap images that has been rendered in the correct scanline orientation.
l Image Complexity:The more complex the picture, the more processing time to print it. This applies to both vector
and bitmap images and is especially true when using gradients. Gradients make vector-based images much larger and
timely to process, and bitmap images remain larger since gradients cannot be easily compressed.
l PDFand EPSfiles:The more images and data PDFs and EPS files contain, the more time they take to process. This
is especially true if these files contain images.
l Multipage PDFor TIFFfile:Image resources like PDFfiles and TIFFfiles may contain multiple pages, and all their
pages will be processed even if they are not all used in the document. If you are not using a large number of pages, it is
better to remove them from the image resource.
Modifying and Updating Images
Internal Images can be modified and updated in many different ways.
To edit an internal image resource:
1. In the Structure area, select the image resource you want to edit.
2. In the Object Inspector, locate the Edit image property, click the property value and click the edit button that
appears on the far right of the property value.
PlanetPress Design launches the image editor. If the image resource is a bitmapped image resource (an image
resource in GIF, TIFF, PNG or BMP format), PlanetPress Design launches the image editor you defined in the User
Options dialog box. If you did not define an image editor in the User Options dialog, or if the image resource is in either
PDF or EPS format, PlanetPress Design launches the default editor defined for those formats in Windows.
3. Edit the image resource.
4. Save the changes and exit the image editor.
To resample an internal image resource (adjust the pixel dimensions), do either of the following:
l In the Object Inspector, adjust the pixel height or pixel width of the image resource that static image references. Note
that when you adjust one pixel dimension, PlanetPress Design automatically adjusts the other dimension to preserve
the aspect ratio of the image. Also note that resampling an image resource in the Object Inspector has an irreversible
effect on image quality. If you want to restore both the original pixel dimensions and the original quality of the image
resource, you must add the image resource to the document again.
l Open the image resource the picture object references in an image editor and adjust its pixel dimensions
Any picture objects that reference that image resource update to reflect the new pixel dimensions.
©2010 Objectif Lune Inc - 180 -