CopiaFacts can be configured to process multiple Image Option sets in turn, for converting documents containing one or more 'difficult' pages where 'compression' for faxing creates a huge document file which takes a long time to transmit. Since fax compression is designed to optimize text documents only, it can increase the data to be transmitted for images and colored backgrounds. Such pages can produce images which take ten minutes or more to transmit. However in many cases the aggressive processing needed to convert pictures and colors efficiently can reduce the quality of the majority of 'normal' documents, and so needs to be avoided unless actually needed.
The successful selection of an optimal conversion can usually improve the legibility and quality of the fax document, as well as reducing its transmission time. However these two objectives can sometimes be in conflict.
The feature is implemented using an Image Options keyword of TRYnn/s, where nn is a sequence of one or more digits representing an image option set to try next, and s is the size in kilobytes of the converted page which, if exceeded, would cause the alternate set to be tried.
For example, adding TRY5/100 as an option keyword in your default option set 0 would cause option set 5 to be tried next for a page which exceeds 100kb of compressed data. And TRY56/100 would first try option set 5, and if the compressed data still exceeded 100kb would then try option set 6. If the size still exceeds 100kb, the option set which produced the smallest size will be used; this might involve a repeated conversion if the last try was not the smallest.
Before using this feature, there are some important issues to be aware of:
•Copia provides sample Image Option sets designed for specific types of 'difficult' document. You should review these before simply applying them, because it will waste conversion time if you try conversion options designed for documents which you are unlikely to encounter.
•This feature is only implemented in the Document Converter (FFEXTERN and CVSINGLE) and not for on-the-fly conversions in the COPIAFACTS engine. It is also not processed in the FFVIEWER image options editor, which handles and test-converts only one option set at a time.
•Image Option Sets only affect the built-in document converters, which are the default conversion method; if you have opted to use the CopiaFacts printer drivers for document conversion, you will only have available the printer property settings to control conversion to a faxable TIF document.
•The size comparisons of Option Set results are done on a page-by-page basis. This avoids repeated conversion of multi-page documents when most pages contain normal text and do not require special processing.
•The replacement of Option Sets only affects the option keywords for Image Correction and Transformation. The size, scaling, and initial rendering are controlled by the first selected image option set. Resolution and fax encoding changes will be ignored when attempting a page conversion with alternate option sets, because some fax boards and ports cannot accommodate such changes in mid-document. You should base your size threshold on the chosen resolution and fax encoding for the initial or default image option set.
•Because of the way TIF files are constructed, the output TIF file size may reflect the worst-case conversion results. However the optimized conversion will be contained in only part of this space, and TIF readers only need to read the parts of the file containing the image strips. So even if using this feature still results in large files, in many cases they will have mostly unused space. The FFVIEWER information display now shows the data size as well as the file size, and saving the file from FFVIEWER would reduce its size. But the Document Converter does not rewrite the file for this purpose, because to do so would merely make the conversion take longer, without affecting transmission time.
•It is recommended that you add a TRY option only on the default or initial option set chosen. The default Image Option Set is set 0, and you can select an different Image Option Set with a $convert_options IMGn option (this command can be placed in a USR./UJP file or in an FS file). These option sets (by convention, lower numbered sets) might then contain a TRY option, and option sets without a TRY (by convention, higher numbered sets) would then supply the special conversions needed for each type of 'difficult' document.
•The sizes of rendering attempts are saved, but to conserve resources the results are currently not saved. Configuring to select the smallest conversion may involve an extra rendering operation if the last attempt did not produce the smallest result. It is also very important to remember that the smallest size file is not always the best one. You may have created an option set which works well for one type of input document but which changes important parts of another document type to blank space, which compresses excellently.
•We recommend avoiding the use of the IMAGE_OPTIONS override variable when you plan to try multiple option sets. If you have override options similar to an existing option set, you may waste a test conversion on an image option set which is going to produce a similar result to the one you started with.
•To monitor conversion attempts, run FFTRACE on the machine running FFEXTERN and CVSINGLE, and add BMP2TIF under File/Applications.
•If using this feature is overkill for a site with few 'difficult' documents to send, you can simply extend the timeouts (using variable overrides such as BLADEWARE_SENDPAGE_TIMEOUT_MINUTES or DIVA_PAGE_SEND_TIMEOUT_SECONDS). This may tie up one of your own fax channels, and those of your recipients, for much longer than necessary, but it involves no special configuration. If your fax senders are all your own employees, the other useful option is to show them how simple changes to the original documents to meet the constraints of faxing could speed up the delivery of documents from them and their colleagues, and more importantly could improve document appearance and quality at the destination.
Before setting up a sequential pair or chain of option sets, it is essential that you first load some sample documents in the Image Options Editor as described here and determine the best options for your own typical documents.
 | If you need help selecting the best options, please gather examples of any problem documents for which you need to improve either quality or transmission time and send them to Copia Support for advice and suggested options. By all means delete or obfuscate any confidential or identifying information first. With your permission, we may wish to include small snippets of such examples in future editions of this manual to illustrate the before/after affect of image transformations for the benefit of other users. |
Syntax Examples
The tests described below are applied when a page has been converted and compressed, and the resulting size of the data created with the current settings has been calculated:
| (no TRY keyword) | When this is an option on the default or initial option set selected for a document, the resulting conversion will be used whatever its size. |
| When this is the option set selected for a page as an alternate, the subsequent attempts are controlled by the TRY settings encountered for the document. |
| TRY56/100 | When this is an option on the default or initial option set selected for a document, if the size with these settings is less that 100kb, the conversion will be used and no further conversions will be done for the page. If not, the page will be reconverted using option sets 5 and then 6, and if either result is less than 100kb, the conversion will be used and the next attempt skipped. If the size remains over 100kb, the smallest conversion will be used. |
| When this is an option on an option set selected for a page as an alternate (not recommended), the option set numbers and threshold will replace the originals, and processing will continue as if this was the initial option. Any untried option sets from the previous TRY option will be ignored. |
Note that as soon as an option set is about to be chosen for use which has already been used for the page, the attempt sequence is terminated and the smallest conversion will be used.
The following sections describe the principles we suggest you employ to optimize the conversion of the documents you expect to have to send by fax.
Specifying a Single Alternate Option Set
It may often be sufficient to specify a single alternate conversion attempt. For example a site which often needs to fax documents with colored backgrounds might define:
$image_options 0 "TRY7/150" ; no options unless size > 150kb
$image_options 7 "BGCOLOR15" ; fix solid colors
The result of this will be that a 'normal' page of headings and text, or a simple HTML cover page, will convert typically to under 30kb and will come nowhere near triggering a second conversion attempt. On the other hand a page with a solid light blue background will 'compress' perhaps to 200kb and will then result in a second conversion using option set 7, which could be expected to reduce its output size to below 60kb.
In this case, it is unlikely that the second conversion would ever create a bigger result. This means that a document containing a full-color photograph, for example, will still create a large-size fax document because the BGCOLOR transformation will not detect a predominance of a single color. For faxing a full-color photograph, it may sometimes be necessary to accept a long transmission time, though improvements can be made, as discussed below.
Using the Smaller Result of Two Option Set Conversions
If your users frequently have to fax full-color or grayscale documents, for example medical images, some improvements can often be made. You will first need to experiment with some sample documents using the Image Options Editor, and this example assumes you have found an option set which usually, though not always, produces a better result. In this case you might define:
$image_options 0 "TRY8/300" ; no options unless size > 300kb
$image_options 8 "GAMMA1.2 CONTRAST" ; improve most pictures
If the first conversion of the page has exceeded the 300kb threshold, then if the second conversion with option set 8 makes a smaller page data size, it is used; if it makes a larger page data size, the first conversion of the page is repeated and then used unconditionally.
Using more than two Option Sets
Combining the two earlier examples is also possible, when you have more than one type of 'difficult ' documents. For these two specific examples, option set 2 might improve both types of document somewhat, but option set 1 will have a bigger effect on documents of the first type, so it makes sense to try it first. So one approach would be simply to chain from one to the other.
$image_options 0 "TRY78/300" ; no options unless size > 300kb
$image_options 7 "BGCOLOR15" ; fix solid colors
$image_options 8 "GAMMA1.2 CONTRAST" ; improve most pictures
The sequence this time operates as follows: simple documents are processed with the first conversion. If the 300kb is exceeded, option set 7 is given a chance to reduce the size, and is used if it succeeds. If not, the size will be the same after option 7 has been used, and option set 8 will then have a chance to reduce it. If not, then the smallest size over 300kb so far will be used: if the smallest is not the last one, its conversion will be re-done.
