|
JPEG compression options
You may choose whether to export files compressed or uncompressed using the checkbox on the 'Advanced' page of the Configuration dialogue for PDF format: see Setting options for PDF export.
If the file is to be compressed, standard data compression methods which reduce the file's size without losing information are applied to the entire document. When exporting to PDF, however, you may choose to treat the images in the document differently, by applying JPEG compression techniques.
JPEG compression can reduce file sizes considerably, but at the expense of the image's quality. JPEG compression is not useful for monochrome images. It may be detrimental to detailed images with sharp lines, as information on colour and luminance may be lost. "Trial and error" will be required by all but the most expert in setting JPEG compression parameters to minimize file-size while maintaining the required quality of image in the output document.
| 2. | Enter/select a value for Use JPEG for images. This sets a benchmark to determine whether JPEG compression is used or not:
100 always use JPEG compression
0 never use JPEG compression
Intermediate values bias the set-up towards or away from using JPEG compression; EscapeE defaults to using a value of 50. |
| 3. | Tick the Low resolution colour checkbox to effectively average the colour (rather than the luminance) of a number of pixels, yielding a smaller number of "bigger" colour pixels. This results in smaller images with some loss of quality - sharp edges may appear fuzzy and colours smeared out, but this is usually acceptable for photographs. |
| 4. | Enter/select a value for image Quantisation quality:
100 for minimal degradation, but bigger files than
0 for heavily quantised (i.e. highly compressed but low quality) images.
Intermediate values may be used to vary the degree of quantization; the default value used is 50. |
| 5. | Tick the Coarse colour quantisation checkbox to allow the colour to be rounded to fewer levels (fewer than the luminance values), again yielding smaller images with some loss of quality. This may be acceptable for graphic art using limited palettes. |
Image trimming
| 2. | Select an Image option:
Paper size only The image is trimmed to the size of the selected paper.
Printed region only White space is removed to leave the smallest rectangle which will contain all the printing.
Printable region only The image is trimmed to the area of the page which a PCL printer would print on.
Selected area only Outputs the area that has been swept out. If an area has not been swept out, the first field found is used to define the area. If neither an area nor a field can be found, the default ("Full", see below) is used.
Full The default. The whole page is output, including any items which fall outside the area of the page. |
| 3. | If you would like to add a Border around the trimmed image, key-in the width of the Left, Top, Right, Bottom borders and select the appropriate units: Cm, Inches or Pixels. For example, 1,3,1,3 adds 1 unit to the sides and 3 units to the top and bottom of the image. |
See also
Exporting files to PDF
Image compression
|
