Tag Archive for conversion

Converting from CGM to Postscript

November 24, 2009 2 comments

On 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. The history is that it was developed at the U.K.’s Rutherford Appleton Laboratory but it seems that it was left 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 want to find out more, here’s a PDF rendition of the help file that comes with the thing:

RALCGM Documentation

Graphics, Imaging, Software

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Harnessing the power of ImageMagick

October 26, 2008 No comments

Using the command line to process images might sound senseless but 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 and 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 but a bit of judicious post processing will turn things around. Here’s a command that’ll do the trick:

convert -page 792×612+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.

Graphics, Imaging, Linux, Software, UNIX

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The irritation of a 4 GB file size limitation

November 20, 2007 No comments

I recently got myself a 500GB Western Digital My Book, an external hard drive in other words. Bizarrely, the thing is formatted using the FAT32 file system. I appreciate that backward compatibility for Windows 9x might seem desirable but using NTFS would be more understandable, particularly given that the last of the 9x line, Windows ME, is now eight years old (there cannot be anybody who still uses that, can there?). The result is that I got core dump messages from cp commands issued from the terminal on my Ubuntu system to copy files of size in excess of 4GB last night. It surprised me at first but it now seems to be a FAT32 limitation. The idea of formatting the drive as NTFS did occur to me but GParted would not do that, at least not with my current configuration. The ext3 file system is an option but I have a spare PC with Windows 2000 so that will be a step too far for now, unless I take the plunge and bring that into the Linux universe too.

Other than the 4GB irritation, the new drive works well and was picked up and supported by Ubuntu without any hassle beyond getting it out of the box, finding a place for it on my desk and plugging in a few cables. While needing judiciousness about file sizes, it played an important role while I converted a 320 GB internal WD drive from NTFS to ext3 and may yet be vital if my Windows 2000 box gets a migration to Linux. In interim, 500 GB is a lot of space and having an external drive that size is a bonus these days. That is especially the case when you consider that the 1 terabyte threshold is on the verge of getting crossed. It certainly makes DVD’s, flash drives and other multi-gigabyte media less impressive than they otherwise might appear.

Hardware, Linux, Operating Systems, Windows

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