We often get asked about the resolution of spatial images and the affects of scaling them in Adobe Illustrator CS4. When scaling an image in Adobe Illustrator (using the Scale tool or the MAPublisher Register Image function) it will not resample the image (the image still has the same number of pixels). So effectively scaling down an image increases the image PPI (pixels per inch). In terms of geographic image resolution (size of a pixel in world unit), it does not change. The image resolution is dependent on the source of collection. To view the PPI of an image, make sure the Adobe Illustrator Control tool bar is enabled (Window menu >, Control). If an image is reduced by 50% then the PPI is multiplied by 2. The placed image below shows a PPI of 72. After scaling the image to 50%, the PPI increases to 144. When you use MAPublisher Register Image, it will always perform a uniform scaling (same horizontal and vertical percentage). Your PPI will vary depending on the scale and size of your artboard. How does this affect your workflow? It is important to consider the medium of final distribution for the image so that you can determine an image resolution to use. As a general guide: Source.