PDF Driver includes six predefined conversion controls which specify settings for compressing text and graphics (line art) as well as specific compression settings for color images, grayscale images, and monochrome (black-and-white) images. Compression helps make your PDF files smaller.
You can select the appropriate level from the drop-down list:
- Medium Quality (level 50) (default)
- High Quality (level 75)
- Low Quality (level 25)
- Lossless (level 100)
- Image Place Holder (level 5)
- No Image (level 0)
Set level 0 to have pictures in the source document dropped from the PDF. Select level 5 to have very low quality images, serving only as place-holders.
You can edit the settings for an existing control, add a new control, or delete an existing control in the Compression Controls dialog box.
To display the Compression Control dialog box:
- Click the Advanced button.
- Highlight a conversion control in the list of conversion controls and view or edit the settings as needed.
Modify the Auto-setting
Move the slider from a pre-set value to a value of your choice. This affects the compression for texts, line art and images in your documents.
Use Custom Settings
Select a compression method for any color, grayscale, or monochrome images in your document. For color and grayscale images, you can choose from a range of qualities of JPEG and ZIP formats, from High to Low.
Which method is best depends on the kind of images in your particular document. Some compression techniques do not lose any detail in the original: these methods are called “lossless.” Lossless methods do not save as much disk space as the other kind of compression, which is called lossy. Files compressed using lossy methods can be much smaller than files using lossless methods.
For example, JPEG is best for images requiring a smooth transition from one color or shade to another while ZIP works well for sharper changes. For best results, you might want to try different compression settings for different documents.
The default value for each of the predefined conversion controls allows the print driver to choose the best method based on the nature of the image. For monochrome images, you can choose from ZIP, CCITT Group and Run Length encoding.
- CCITT (International Coordinating Committee for Telephony and Telegraphy) compression method works best for black-and-white images made by paint programs and 1-bit scanned images.
- Run Length produces the best results for images that contain large areas of solid white or black.
- Select or clear the ReSample setting. Resampling changes the pixel dimensions (and thus the display size) of an image.
- If you choose to ReSample, specify either DownSample or SubSample from the pull-down menu. The default setting is DownSample.
Downsampling decreases the number of pixels in the image. Each pixel it places has the average value of all the pixels it replaces. Subsampling chooses a pixel in the center of the sample area and replaces the entire area with that pixel at the specified resolution.