Written by: Paul H. Yoshimune April 27, 1994
When using Image Alchemy PS to render an image, there are two ways to change the final output size: render the image to the desired size directly, or render to some intermediate size (such as the original image size) and then raster scale the image.
The memory and disk space requirements and processing time can increase dramatically when rendering PostScript images directly for use on large format devices. For example, rendering a full colour PostScript image to 34 inches by 44 inches at 300dpi (the size of a Novajet plotter) requires up to 800 megabytes of disk space.
A way to reduce the memory requirement is to render the image to an intermediate size and then use Alchemy PS's raster scaling operators (-X and -Y) to increase the image to its final size. This requires much less disk space since the raster scaling is done on the fly.
For example, rendering the same image to 17" x 22" and then raster scaling it to 34" x 44" reduces the disk space requirements to 200 megabytes; and rendering to 8.5" x 11" and then raster scaling to 34" x 44" requires only 50 megabytes.
Performing the image scaling in two steps may reduce the quality of the final image somewhat, but generally the results will be indistinguishable from rendering the PostScript file directly to the final size.
For example, both of these command lines will generate the same size image:
alchemy tiger.ps --r7 -Zo 34i 44i -Z+
alchemy tiger.ps --r7 -Zo 8.5i 11i -Z+ -Xb34i -Yb44i -+
The first will render the PostScript file directly to 34" x 44", and hence will require lots of disk space and time. The second will render to a much smaller 8.5" x 11", and then raster scale the image to the final output size of 34" x 44". This method will require much less time and disk space. Again, the output quality will be slightly better with the first method, but the tradeoff is increased resource requirements.