Open formats | Technology Tales

Converting from CGM to Postscript

24^th November 2009

One thing that I recently had to investigate was the possibility of converting CGM vector graphics files into Postscript and from there into PDF. Having used ImageMagick for converting images before, that was an obvious option. However, that cannot process CGM files on its own and needs a delegate or helper application as well. This is the case with raw digital camera files too, with UFRaw being the program chosen. For CGM images, the more obscure RALCGM is what's needed, and tracking it down is a bit of an art. Though the history is that it was developed at the U.K.'s Rutherford Appleton Laboratory, it appears that it was left to go off into the wilderness rather than someone keeping an eye on things. With that in mind, here are the installation packages for Windows and Linux (RPM):

Windows Installer

Linux RPM

RALCGM is a handy command line tool that can covert from CGM to Postscript on its own without any need for ImageMagick at all. From what I have seen, fonts on graphical output may look greyer than black, but it otherwise does its job well. However, considering that it is a freely available tool, one cannot complain too much. There are other packages for doing vector to raster conversion and the ones that I have seen do have GUI's but the freedom to look at for cost software wasn't mine to have. The required command looks something like the following:

ralcgm -d PS -oL test.cgm test.ps

The switch -d PS uses the software's Postscript driver and -oL specifies landscape orientation. If you like to find out more, here's a PDF rendition of the help file that comes with the thing:

RALCGM Documentation

Bumping newly edited older articles in Textpattern

10^th July 2009

Whether this is intended or not, you can put a pre-existing article to the top of your website's Atom or RSS feed by saving it as draft while it is being modified before restoring its status to live again. This is handy when you have got permanent articles that you are enhancing over the course of time, and you want to give your visitors a reason to return and maybe even prompt search engines too. Though new articles will achieve this always, it's nice to see that older articles don't get lost in space either. While this may be a hack, I am using Textpattern for permanent postings, rather than blogging, so I remain well pleased to see the availability of the feature.

Harnessing the power of ImageMagick

26^th October 2008

Using the command line to process images might sound senseless, only for the tools offered by ImageMagick certainly prove that it has its place. I have always been wary of using bulk processing for my digital photo files (some digitised from film prints with a scanner) but I do agree that some of it is needed to free up some time for other more necessary things. With this in mind, it is encouraging to see the results from ImageMagick and I can see it making a major difference to how I maintain my online photo gallery.

For instance, making thumbnail images for the gallery certainly seems to be one of those operations where command line bulk processing comes into its own, and ImageMagick's own convert command is heaven sent for this one. For resizing images, all that's needed is the following:

convert -resize 40% input.jpg output.jpg

Add a spot of further shell scripting and even a dash of Perl and the possibilities for this sort of thing become clearer, and this is but the pinnacle of the proverbial iceberg. The -rotate switch will do what the name suggests, while there are a whole plethora of other options on tap. So long as you have Ghostscript on your system, conversion of graphics to Postscript (and Encapsulated Postscript too) and PDF files is possible with the -page option controlling the margin around the image itself in the resulting outputs. Unfortunately, portrait is the sole orientation on offer, yet a bit of judicious post-processing will turn things around. Here's a command that'll do the trick:

convert -page 792x612+72+72 input.png ps2:output.ps

For retrieving image metadata like its resolution and size, the identify command comes into play. The -verbose option invokes the output of all manner of image metadata, so using grep or egrep is perhaps advisable, especially for bulking processing with the likes of Perl. Having the ability to stream image metadata makes loading databases like MySQL less of a chore than the manual data entry that has been my way of doing things until now.

Another way to control line breaks in (X)HTML

22^nd October 2008

While you can use <br /> tags, there is another way to achieve similar results: the   or non-breaking space entity. Put one of them between two words, and you stop them getting separated by a line break; I have been using this in the latest design tweaks that I made to my online photo gallery. Turning this on its head, if you see two words together acting without regard to normal wrapping conventions, then you can suspect that a non-breaking space could be a cause. There might be CSS options too, but their effectiveness in different browsers may limit their usefulness.

Ghostscript: **** Unable to open the initial device, quitting.

6^th October 2008

The above error message has been greeting me when creating PDF's with Ghostscript on a Solaris box and does need some translation. If you are directing output to a real printer, I suppose that it is sensible enough: nothing will happen unless you can connect to it. It gets a little less obvious when associated with PDF creation and seems to mean that the pdfwrite virtual device is unable to create the specified output file. A first port of call would be to check that you can write to the directory where you are putting the new PDF file. In my case, there appears to be another cause, so I'll have to keep looking for a solution.

Update: I have since discovered the cause of this: a now defunct TEMP assignment in the .profile file for my user account. Removing that piece of code resolved the problem.

Combining bookmarked PDF files using Ghostscript

4^th October 2008

My latest adventure in the world of computing has led me into the world of automated PDF generation. When my first approach didn't prove to be completely trouble-free, I decided to look at the idea of going part of the way with it and finishing off the job with the open-source utility Ghostscript. It is that which got me thinking about combining bookmarked PDF files and I can say that Ghostscript is capable of producing what I need as long it doesn't generate any errors along the way. Here's the command that does the trick:

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=final.pdf source_file1.pdf source_file2.pdf

The various switches of the gs command have very useful roles with dBATCH ensuring that Ghostscript shuts down when all is done, dNOPAUSE removing any prompts that would otherwise be given, q for quiet mode, sDEVICE using Ghostscript's own PDF creation functionality and sOutputFile creates the output file, stopping Ghostscript from sending it to its default stream. All of this applies to Windows Ghostscript too, though the name of the executable is gswin32c for 32-bit Windows instead of gs.

When it comes to any debugging, it is useful to consider that Ghostscript is case-sensitive with its command line switches, something that I have seen to trip up others. I am getting initial device initialisation, so it strikes me that dropping some of the ones that reduce the number of messages might help me work out what's going on. It's a useful idea that I have yet to try.

There is also online documentation if you fancy learning more, and Linux.com has an article that considers other possible PDF combination tools as well. All in all, it's nice to have command line tools to do these sorts of things rather than having to use GUI applications all the time.

Eliminating Peekaboo content display problems in Internet Explorer

1^st July 2008

Recently, I changed the engine of my online photo gallery to a speedier PHP/MySQL-based affair from its PHP/Perl/XML-powered predecessor. On the server side, all was well, but a peculiar display issue turned up in Internet Explorer (6, 7 & 8 were afflicted by this behaviour) where photo caption text on the thumbnail gallery pages was being displayed erratically.

As far as I can gather, the trigger for the behaviour was that the thumbnail block was placed within a DIV floated using CSS that touched another DIV that cleared the floating behaviour. I use a table to hold the images and their associated captions in place. Furthermore, each caption was also a hyperlink nested within a set of P tags.

The remedy was to set the CSS Display property for the affected XHTML tag to a value of "inline-block". Within a DIV, TABLE, TR, TD, P and A tag hierarchy, finding the right tag where the CSS property in question has the desired effect took some doing. As it happened, it was the tag set, that for the hyperlink, at the bottom of the stack that needed the fix.

Of course, it's all very fine fixing something for one browser, but it's worthless if it breaks the presentation in other browsers. In that vein, I did some testing in Opera, Firefox, Seamonkey and Safari to check if all was well and it was. There may be older browsers, like versions of IE before 6, where things don't appear as intended, yet I get the impression from my visitor statistics that the newer variants hold sway anyway. All in all, it was a useful lesson learnt, and that's never a bad thing.

Are developers and designers overcomplicating their CSS?

11^th May 2007

When I have been tweaking the widgets in this blog, the thought crossed my mind that purveyors of open source blogging and CMS's may be overcomplicating matters with the CSS that they are writing. Using inheritance without much thought as to others having to pick it up is one irritation, but bunching styles together can confuse too. For instance, you can draw from two different styles for the same HTML element (it's what's going when you see class="class1 class2" in a tag definition), which is OK if done simply but can confuse matters when customisation is attempted later. Drupal particularly suffers from this bugbear, but it's there on WordPress too, though not to the same extent. Using a hierarchy to define and attach your styles (#id1 .class2 tag1 {style definition...} is the kind of thing that I have in mind), can also confound, even if I admit to finding the approach very useful for myself. I think that I know what's driving this: the need to cut down the bulk of CSS files but using the advanced features that I mentioned above without clear commenting and other documentation hampers later efforts. It would be nice if every developer of a theme to use in blogging or CMS software was forced to document their work extensively and share that documentation with interested users. After all, sharing is the whole purpose of their endeavours...

A selection of useful tools and technologies for contemporary web development

23^rd March 2007

Having been on a web-building journey from Geocities to having a website with my own domain hosted by Fasthosts, it should come as no surprise that I have encountered a number of tools and technologies over this time and that my choices and knowledge have evolved too. I’ll muse over the technologies first before going on to the tools that I use.

Technologies

XHTML

When I started building websites, it was not after HTML 4 got released, and I devoured most if not all of Elizabeth Castro’s Peachpit Visual Quickstart guide to the language within a weekend. Having previously used fairly primitive WYSIWYG tools like Netscape Composer and Claris Home Page, it was an empowering experience and the first edition (it is now on its third) of Jennifer Niederst Robbins’ Web Design in a Nutshell took things much further, becoming something of a bible for a number of years.

When it first appeared, XHTML 1.0 wasn’t a major change from HTML 4, but its stricter more XML-compliant syntax was meant to point the way to the future and semantic markup was at its heart at least as much as it was for HTML 4. XHTML 2.0 is on the horizon and after the modular approach of XHTML 1.1 (which I have never used), it will be interesting to see how it develops. Nevertheless, there is a surprising development in that some people are musing over the idea of having an HTML 5. Let’s hope that the (X)HTML apple cart doesn’t get completely overturned after some years of relative stability. I still bear scars from the browser wars raging in the 1990’s and don’t want to see standards wars supplanting the relative peace that we have now. That said, I don’t mind peaceful progression.

CSS

Only seems to be coming into its own in the last few years and is truly a remarkable technology despite the hobbles that MSIE places on our ambitions. CSS Zen Garden has been a major source of ideas; I wouldn’t have been able to customise this blog as much as I have without them. I was an early adopter of the technology and got burnt by inconsistent browser support; Netscape 4 was the proverbial bête noir back then, fulfilling the role that MSIE plays today. In those days, it was the idea of controlling text display and element backgrounds from a single place that appealed. Since then, I have progressed to using CSS to replace table-based layouts and to control element positioning. It can do more…

JavaScript

Having had a JavaScript-powered photo gallery before my current Perl-driven one, I can say that I have definitely sampled this ever-pervasive scripting language. Being a client-side language rather than a server-side one, it does place you rather at the mercy of the browser purveyors, and it never ceases to amaze me that there is a buzz around AJAX because of this. In fact, the abundance of AJAX cross-browser function libraries is testimony to the need for browser-specific code. Despite my preferences for server-side scripting, I still find a use for JavaScript, and its main use for me these days is to dynamically control CSS elements to do such things as control the height of a page element or whether it is shown or not. Apparently, CSS may get some dynamic capabilities in the future and reduce my dependence on JavaScript. Meanwhile, Jeremy Keith’s DOM Scripting (Friends of Ed) will prove as much of an asset as it has done.

XML

These days, a lot of the raw data underlying my personal website is stored in XML. I did try to dynamically transform the display of the XML into something meaningful with CSS and XSLT when I first scaled its dizzy heights, but I soon resorted to other techniques. Browser support and the complexity of what I required were the major contributors to this. The new strategy involved two different approaches. The first was to create PHP/XHTML pages from the precursor XML offline, and this is how I generate the website’s directory pages. The other one is to process the XML as text to dynamically supply an XHTML page as the user visits it; this is the way that the photo gallery works.

Perl

This still powers all of my photo gallery. While thoughts of changing it all to PHP linger, there is a certain something about the Perl language that keeps it there. I suppose it is that PHP is entangled in the HTML while Perl encases the whole business, and I am reasonably familiar with its syntax these days, which is why it still does a lot of the data processing grunt work that I need.

PHP

PHP is everywhere these days, though it doesn’t attract quite the level of hype that used to be the case. It still appears with its sidekick MySQL in many website applications. Blogging software such as WordPress and content management systems like Drupal, Mambo and Joomla! wouldn’t exist without the pair. It appears on my website as the glue that holds my visitor directories together and is the processing engine of my WordPress blog. And if I ever get to a Drupal element to the site, by no means a foregone conclusion though I am spending a lot of time with it at this time, PHP will continue its presence in my website scripting as it powers that too.

Applications

Macromedia HomeSite

I have a liking for hand coding, so this does most of what I need. When Macromedia (itself since taken over by Adobe, of course) took over Allaire, HomeSite sadly lost its WYSIWYG capability, but the application still soldiers on even though Dreamweaver offers a lot to code cutters these days. Nevertheless, it does have certain advantages over Dreamweaver: it is a fleeter beast to start up and colour codes Perl syntax.

Macromedia Dreamweaver

There was a time when Dreamweaver was solely a tool for visual web page development, but the advent of Dreamweaver UltraDev added server-side development capabilities to the Dreamweaver family. These days, there is only one Dreamweaver version, but UltraDev’s capabilities still live on in the latest version and I would not be surprised if they were taken further in these database-driven times.

Nowadays, Dreamweaver isn’t an application where I spend a great deal of time. In former times, when my site was made up of static HTML pages, I used Dreamweaver a lot, even if its rendering capabilities were a step behind the then-current browser versions. I suppose that it didn’t fit the way in which I worked, but its template-driven workflow would have been a boon back then.

However, my move from a static site to a dynamic one, starting with my photo gallery, has meant that I haven’t used it as much since then. However, with my use of PHP/MySQL components on my site. Its server-side abilities could get the level of investigation that its PHP/MySQL capabilities allow.

Altova XMLSpy Professional

Adding MySQL databases to my web hosting costs money, not a lot, but it could be spent on other (more important?) things. Hence, I use XML as the data store for my photo gallery and XML files are pre-processed into XHTML/PHP pages for my visitor directories before uploading onto the server.

I use XMLSpy to edit and manage the XML files that I use: its ability to view XML in grid format is a killer feature as far as I am concerned and XML validation also proves very useful; particularly when it comes to ensuring that DTD’s and XML files are in step and for the correct coding of XSLT files. There are other features that I need to explore and that would also take my knowledge of the XML further to boot, not at all a bad thing.

Saxon

For processing XML into another file format such as XHTML, you need a parser and I use the free version of Saxon to do the needful, Saxonica offers commercial versions of it. There is, I believe, a parser in XMLSpy, but I don’t use it because Saxon’s command line interface fits better into my workflow. This is a Perl-driven process where XML files are read and XSLT files, one per XML file, are built before both are fed to Saxon for transforming into XHTML/PHP files. It all works smoothly and updating the XML inputs is all that is required.

AceFTP

If I were looking for an FTP client now, it would be FileZilla, but AceFTP has served me well over the last few years, and it looks as if that will continue. It does have some extra features over FileZilla: transfers between remote sites, and scheduling, for example. I have yet to use either, but they look valuable.

Hutmil

In bygone days when I had loads of static HTML files, making changes was a bit of a chore if they affected every single file. An example is changing the year on the copyright message on the page footers. Hutmil, which I found on a magazine cover-mounted disc, was a great time saver in those days. Today, I achieve this by putting this information into a single file and getting Perl or PHP to import that when building the page. The same “define once, use anywhere” approach underlies CSS as well, and scripting very usefully allows you to take that into the XHTML domain.

Apache

Apache is ubiquitous these days, and both the online and offline versions of my site are powered by it. It does require some configuration, but it is a powerful piece of kit. The introduction of 2.2.x meant a big change in the way that configuration files were modularised and while most things were contained in a single file for 2.0.x, the settings are broken up into different files in 2.2.x, and it can take a while to find things again. Without having it on my home PC, I would not be able to use Perl, PHP or MySQL. Apart from this, I especially like its virtual site capability; very useful for offline development.

WordPress

My hosting supplier offers blogs on Blogware, but that didn’t offer the level of configuration that I would have liked. It is true that this is probably true of any host of blogs. I can’t speak for Blogger, but WordPress.com does have its restrictions too. To make my hillwalking blog fit in with the appearance of my photo gallery, I went popped over to WordPress.org to download WordPress so that I could host a blog myself and have maximum control over its appearance. WordPress supports themes, so I created my own and got my blog pages looking as if they are part of my website, rather than looking like something that was bolted on. Now that I think of it, what about WordPress supporting user-created themes? I support that there is the worry of insecure PHP code but what about it?

MySQL

I am between minds on whether this is a technology or a tool. SQL certainly would be a technology standard, but I am not so clear on what MySQL would be. In any case, I have classed it as a tool, and a very useful one at that. It is the linchpin for my WordPress blogs and, if I go for a content management system like Drupal, its role would surely grow. While I do have a lot of experience with using SAS SQL and this helps me to deal with other varieties, there is still a learning curve with MySQL that gets me heading for a good book and Kofler’s The Definitive Guide to MySQL5 (Apress) seems to perform more than adequately in this endeavour.

Paint Shop Pro

As someone who hosts an online photo gallery, it won’t come as a surprise that I have had exposure to image editors. Despite various other flirtations, Paint Shop Pro has been my tool of choice over the years, but it is now set to be usurped by a member of Adobe’s Photoshop family. Paint Shop Pro does have books devoted to it, but it appears that Photoshop gets better coverage and I feel that my image processing needs to be taken up a gear, hence the potential move to Photoshop

HTML Tidy for Windows

22^nd March 2007

Drupal has modules (Import HTML and its helper Static HTML together make up one option) for importing static (X)HTML pages into its database, and it needs HTML Tidy to work. Since I am playing with the thing on Windows, I went out and snagged the version for that OS. Being either lazy or bloody-minded, I tried an XHTML page with PHP code embedded in it and, needless to say, the thing choked. I must try it with plain XHTML instead.

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