PDF File Size Controls

These settings can be included in sprint control streams and a document’s PDF properties.

The PDF setting $^_p268_compress activates compression for text and line art. Use the value 1, ie. $^_p268_compress=1.

The PDF settings $^_p268_compress_mono, $^_p268_compress_grey, and $^_p268_compress_color define the compression level for images.

The tables below list the values that represent each level of compression:

$^_p268_compress_mono

Defines compression level for monochrome images, for example $^_p268_compress_mono=2.
Value	Compression Level
-1	Automatic
0	None
2	CCITT Group 3 Compression
3	CCITT Group 4 Compression
4	Flate (Zip) Compression

$^_p268_compress_grey

Defines compression level for greyscale images, for example $^_p268_compress_grey=4.
Value	Compression Level
-1	Automatic
0	None
4	Flate (Zip) Compression
5	JPEG Compression For information on how to set the quality of these images in output, see Quality Level for JPEG Compression .

$^_p268_compress_color

Defines compression level for color images, for example $^_p268_compress_color=-1.
Value	Compression Level
-1	Automatic
0	None
4	Flate (Zip) Compression
5	JPEG Compression For information on how to set the quality of these images in output, see Quality Level for JPEG Compression

The PDF setting $^_p268_grey_quality defines the quality of greyscale images that are compressed to JPEG level, for example $^_p268_grey_quality=0.

Value	Quality
0	Minimum
1	Low
2	Medium
3	High
4	Maximum

The PDF setting $^_p268_colour_quality defines the quality of color images that are compressed to JPEG level, for example $^_p268_colour_quality=2.

Value	Quality
0	Minimum
1	Low
2	Medium
3	High
4	Maximum

PTC Arbortext Layout Developer (PTC ALD) now supports the downsampling of images in PDF output. With this feature, you can specify output resolution of graphics when printing to PDF. This can reduce the size of output PDF files for faster delivery.

Separate downsampling options are provided for monochrome, grayscale, and color images. For each, you can choose one of three alogrithms based on your requirements — subsample, average, and bicubic.

Transparency and color profiles for graphics are maintained during the downsampling process. You no longer need to employ passthrough processing methods.

In the PTC ALD UI, downsampling of images is controlled by options in the Compression tab of the PDF Options dialog box. Three options are supported for each type of image— monochrome, grayscale, and color images:

• Subsample — fastest, uses nearest pixel from original image

• Average — uses average of the group of pixels surrounding the nearest pixel from the original image

• Bicubic — slowest but best quality, an enhanced bicubic algorithm

Monochrome images are converted to grayscale to achieve the average values required for Average or Bicubic modes. This may result in a larger PDF file, although downsampling and compression could make it smaller than including the original (Subsample method).

Downsampling settings have no effect if the Linked Images option (in the General tab of PDF Options) is set to Passthrough.

• monochromeDownsampleMode, greyscaleDownsampleMode, colorDownsampleMode properties — the mode of downsampling to use for each type of image

• monochromeDownsampleThreshold, greyscaleDownsampleThreshold, colorDownsampleThreshold properties — the minimum image DPI that will trigger downsampling for each type of image

• monochromeDownsampleDPI, greyscaleDownsampleDPI, colorDownsampleDPI properties — the DPI to use when downsampling images

• PDFDownsampleMode constant group — the downsampling algorithm to use

When the Mode is set to a value other than Off, and the DPI of an image is equal to or above the value of the Threshold value, the image is downsampled to the value of DPI.