Porthos

Just what the doctor ordered, says Shiuming Lai

Opportunities can come in disguise and provide the motivation to really sort out things that have been put on the back-burner. In this case, the printer I bought last year, an Epson Stylus Color 860, was connected only to my PC. One of the main attractions of that model was its dual input capability, so my PC could connect on the USB and Falcon by Centronics parallel. Very practical in theory (saying that, my PC's large monitor has dual inputs and I also planned to share this with my Falcon but then decided two screens were better - the art of looking busy).

An inexplicable reluctance to enable my USB ports set in, so I just connected it straight to my PC with the existing parallel cable - call it laziness. After all, I only needed to print off some job applications and pages from Macromedia Flash animations.

The turning point came when various digital cameras with USB interfaces made their way into my possession for testing. This, and the Christmas Eve release of Porthos 1.28, the new Atari PDF viewer, prompted me to make the last connection, literally. I routed an extra-long USB cable to the other end of my work bench, to the printer's resting place under my Mega STE, and took the parallel cable to my Falcon.

In case you hadn't noticed, Adobe's Portable Document Format has become the de-facto standard in electronic documentation on the internet and with product manuals. While other standards like RTF and even Word have enjoyed a brief stint and are still employed for text with basic formatting, PDF reigns supreme due to its ability to store complex page layouts. Therefore my test would include printing.

Porthos is named after one of Alexander Dumas' Three Musketeers, and also stands for, "PORtable document format under TOS" - don't you just love these far-fetched name associations!

Reference configuration

• Windows 98 Second Edition
• Acrobat Reader 5.05
• Epson Stylus Color 860
• Epson driver version 5.02, 720 DPI draft

Test configuration 1

• CT2 Falcon
• CENTSCREEN 3.5.0
• MagiC 6.01
• jinnee 1.1
• Epson Stylus Color 860
• NVDI 5.03, Epson Stylus Color 740 driver, 360 DPI draft
• WDIALOG 2.04

Test configuration 2

• CT2 Falcon
• CENTSCREEN 3.5.0
• TOS 7.04
• Epson Stylus Color 860
• NVDI 5.03, Epson Stylus Color 740 driver, 360 DPI draft
• WDIALOG 2.04

Test configuration 3

• MagiC PC 1.20
• jinnee 2.5
• NVDI 5.03, no printer
• WDIALOG 2.04

Test configuration 4

• Mega STE
• TOS 2.06
• NVDI 5.03, no printer
• WDIALOG 2.04

Test configuration 5

• Mega STE
• MagiC 6.01
• NVDI 5.03, no printer
• WDIALOG 2.04

You'll notice in my Falcon test configurations the Epson 860 used NVDI's Epson 740 drivers, since there are no 860 drivers. As far as I can tell, the 860 was the direct replacement for the 760, which itself was a faster and quieter 740 and shared the same cartridges and print head, too.

All of the 860's modes up to the maximum 1,440 DPI are available, though in any of the "best" quality modes like 720 DPI using the special coated paper setting and Epson paper, NVDI drives the head a few passes too many and ends up over-saturating colours such that they bleed and cause definition loss. I found the same happened with the Epson 860 driver in BeOS 5, so the Windows driver is superior.

To evaluate Porthos' rendering accuracy I did two simple tests. First, I drew an 18x18cm square at 0.75pt line width in Word 2000 (9.0.3821 SR-1) and printed it for verification. It was accurate to the millimetre so I then exported the file using Acrobat PDFWriter 3.02 and printed it using my reference configuration. This time, it came out 16.9x16.9cm. Printing it from my Falcon (test configuration 2) gave 17x17cm.

The next test was to print several documents containing a lot of text and images, one copy from each system (Falcon, PC) and compare them by superimposing the pairs of print-outs against a light source. Disregarding the printed area's placement on the page and an error of approximately +1.5mm over a distance of 211mm, the output from Porthos was geometrically similar, so it's just a matter of scaling. Other than that it's as good as spot-on. I suspect NVDI is at fault, since printing the same page using its 720 DPI Best mode gave a further +1.5mm error on top of that.

It's a slightly different story when the text in a document uses fonts that are not embedded. As you can see from our pictures here, the kerning is incorrect, sometimes completely disjointing words. The author, Wolfgang Domröse, explained:

PDF documents show text in different ways

1. So-called base fonts (Courier, Helvetica...) must be available. Only size, color and encoding is stored in the PDF document. These fonts are in the folder, BASEFONT.
2. All other fonts should be embedded. Mostly they are embedded as CFF (Compact Font Format). The CFF driver of the FreeType library (which I must use) is bad. In low resolution (72 DPI or so) there are "jumps" (+/- 1 pixel) horizontally and vertically! I hope this will be fixed soon. There is no problem in high resolution (printer).
3. PDF documents make use of fonts that are neither base nor embedded. They must be substituted. Porthos substitutes these fonts with two multiple master fonts. Substitution is not very good and will be better in one of the next versions.

I can fully confirm the second point. The base-lines of small text may look ragged on-screen but print out perfectly aligned.

For compatibility, Porthos only contains 68000 code, but on my Mega STE under both TOS 2.06 and MagiC 6.01 it would load then immediately generate a 68000 exception and fall over. It also lacks any FPU code, despite reporting when one is present. We understand this situation will change upon the arrival of the rumoured XTOS machine.

Test configurations 1 and 3 were used at 16-bit and 24-bit colour depth respectively. The raster scaling (and all functions except flip and rotate) are handled by NVDI. It doesn't take advantage of large colour ranges for interpolation, so when down-sampling, images with few or very discretely defined colours, like computer screen-shots, can effectively lose a lot of information.

As befits a product from the invers stable, Porthos has a professionally designed and beautifully clear (currently German language only) manual, in PDF, naturally.

Special features
Six different language resource files are at your disposal with more to come, easily selected from within the program. They are: German, English, Dutch, Czech, Italian and Swedish.

The window preferences dialog allows colour adjustments, display caching and monitor pixel size calibration. Another convenient function is the direct export to Papillon, an image editing program not well known outside of Germany. This bypasses having to export documents as bitmaps and manually loading them. Each new sent document opens a new Papillon editing window. Maybe in future we'll see more a more general implementation of object linking so other programs can take advantage of Porthos. Wolfgang told us we can certainly look forward to the following:

I decided to change Porthos from a viewer to a handler. The upcoming 1.3x will be able to export vector graphics as *.CVG for Calamus users. It will be able to change the document information (author, theme...) and the so-called "outlines" with which you can navigate through the document. Adding and changing of "thumbnails" will be one of the next steps. After that, text export and search will be implemented.

Porthos is one of those brilliant little things that makes you wonder why it took so long coming. The future looks bright.
 

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MyAtari magazine - Review #2, January 2002