Processing images places great demand on both the CPU and the memory. The amount of memory required to process an image is directly proportional to the dimensions (paper size), the resolution (DPI), and the bit depth of the image and the other settings of the Printer Driver.
As an example of the amount of memory involved, consider a standard letter-sized (8.5" X 11") document printed in color (24 bit) at 600 dpi. Before saving the generated image to a file, the entire image must first be loaded into the memory. The calculation of the amount of memory required is as follows:
memory required = (number of pixels in image ) X (number of bytes per pixel)
The total number of pixels in an image is equal to:
(resolution x image height) x (resolution x image width)
Additionally, each pixel in a full-color image uses 24 bits (3 bytes) to store color information. Memory calculations for this image can be expressed as:
memory required = (8.5 X 600) X (11 X 600) X 3 = 100980000 bytes = 96.3 MB
At least 96 megabytes of RAM are required to store the generated image in the memory. The Printer Driver also needs memory for image processing and other features, which can also significantly increase memory usage. E.g.: when printing into a 1 bit monochrome image format with dithering turned on, first a 24 bit EMF image is generated and passed to the Printer Driver, which is converted to a 24 bit bitmap image in memory, which is then converted to the final 1 bit image, increasing the memory usage to several times the size of the final image. If the required amount of physical memory (RAM) is not available for the printing process, Windows uses virtual memory. The disk access (reading/writing) operations to and from the hard disk slow down the entire process significantly.
If there is a lot of disk activity during the printing, and the process takes a long time to complete, the processing can be sped up in any of the following ways:
1. Lower the resolution.
2. Disable dithering by selecting “Disable Photo Quality” on the File Formats tab in the Printing Preferences.
3. Set the bit depth to either 8 or 1 bit instead of 24 bit (full color). Dithering must be disabled by selecting “Disable Photo Quality” on the File Formats tab in the Printing Preferences.
4. Decrease the paper size.
5. Add more RAM to the system.
6. Disable text output or OCR.
If the generated image file is too large, the user can try one of the following steps to decrease the size:
1. Lower the resolution.
2. Set the bit depth to either 8 or 1 bit instead of 24 bit (full color).
3. Decrease the paper size.
4. Use a different image file format or compression.
5. Use a different dithering method.