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- Hints and Tips
- 7.2
- • ArcDFS under RISC OS 3 − It has been reported on numerous occasions
- that ArcDFS doesn’t work under RISC OS 3 − not true! (Or at least only
- partly.) If a disc reports a failure, change the disc TITLE (using
- appropriate option) to “”, i.e. an empty string, and hey presto!!
- 7.2
- Why is that necessary? I have not yet had a chance to bury myself in the
- code to find out, I’m afraid.
- 7.2
- Note: The only other option that doesn’t work is Free, but personally I
- don’t think that’s much of a problem. Format and Verify both work OK.
- 7.2
- P.S. Make sure the Step timings are set to those values given in the
- original documentation, as they are reset when upgrading to RISC OS 3.
- R. George, Cambridge.
- 7.2
- • Grey Scales − I frequently use Draw to produce diagrams for inclusion
- in text produced using Impression, or for independent printing. The
- drawing package which comes with RISC OS 3 generally satisfies my needs.
- 7.2
- One facility which I often need is a grey scale which will produce
- distinct shades on my LaserDirect printer, with the minimum of
- ‘graininess’. Ignore the adverts which proclaim 256 Grey Shades! If you
- need a ‘seamless’ transition from black to white, this is fine, but if
- you want to print blocks of greys which all look different, you will be
- lucky to manage 16 shades.
- 7.2
- The simplest approach to this problem is to try using the colours on the
- palette. It can be helpful to have the features of your diagram
- highlighted in blue, red, green, etc on the screen, but how will they
- appear printed in black-and-white? If you use the default palette (which
- I do not!) the 16 colours come out in various shades of grey, as shown
- below. The squares are labelled with the appropriate colour numbers, and
- arranged from white to black. These squares appear on my Impression
- screen, of course, in glorious technicolour.
- 7.2
- I cannot be sure how this will turn out if Paul prints it in Archive,
- but on my printer there are only seven, perhaps just eight,
- distinguishable shades. They are all fairly grain-free, printed at
- 600×600 dpi, so a suitable selection can be used. If you want them to
- appear on the screen as shades of grey, use ‘colours’
- 0 ◰2 1 2 3 4 5(?) 7. If you prefer them displayed in colour, use
- the series 0 ◰2 9 ◰4 ◰5 ◰0 5(?) 11 7.
- 7.2
- I have continued this investigation to attempt to find the best possible
- grey scale using colours not necessarily on the palette. I have
- restricted my investigation to grey ‘colours’, i.e. those using the
- same, or similar, intensities of red, green and blue. That is enough to
- be going on with!
- 7.2
- !Draw allows you to select each of the three components on a scale
- 0−255. The !Palette utility only allows 16 intensity levels for each
- component (producing the 4096 standard colours), so I have started with
- this restriction. Representing the 16 degrees of intensity by the hex-
- digits 0−F, and allowing a difference of only one between the three
- components, I have devised the 16-grey-shades scale shown below.
- 7.2
- How these colours appear on your screen depends on what palette you are
- using. In front of me now, I can see shades of buff/brown, because I
- have modified the standard, rather harsh, palette. You could try setting
- up a palette using these as colours 0−15. The result on the screen is
- pretty horrible! The result in print, however, is quite good, although
- the lighter shades are a bit grainy.
- 7.2
- Using the Fill Colour facility of Draw gives us greater flexibility,
- because we can select from 0−255 for each primary colour. To keep things
- fairly simple, I have tried only ‘pure grey’ shades, in which the
- intensities of redgreenblue are always the same. This gives 256 shades
- to try.
- 7.2
- Using this technique, LaserDirect clearly does not print 256 shades.
- Groups of four consecutive shades always appear identical, so our
- selection comes down to 64 shades. I printed blocks of these shades,
- each identified by the intensity number used for each of the three
- components, 0 = black ... 255 = white. The shades which show the least
- grain are, for some reason, those numbered 243 235 227 219 etc, i.e.
- those whose codes are 8k+3.
- 7.2
- There are 32 such shades, but adjacent ones are very similar in print,
- often apparently identical. In an attempt to create a usable scale, I
- have selected ten of these codes (235 219 203 187 171 155 139 123 99 and
- 67) plus 0 (black) and 255 (white). These are the shades which I will
- try for my next few Draw diagrams. Even these shades show little
- difference between adjacent pairs, and it is desirable to use alternate
- ones only, if possible.
- 7.2
- Colin Singleton, Sheffield.
- 7.2
- • Hard disc usage − How much space do my hard disc files occupy? The
- answer depends on how I try to measure them! My investigations resulted
- in the recovery of 5.6Mb (13%) from an unexpected source which I don’t
- think has been mentioned previously in Archive.
- 7.2
- We all know that the disc usage figures given by *Free and *Count are
- different. *Count returns the total number of data bytes in the files,
- in my case 22.3Mb. *Free returns the total number of bytes used (or
- reserved) on the disc, in my case 42.8Mb. These are different for at
- least two reasons.
- 7.2
- Firstly, disc space is allocated to files in units which vary from drive
- to drive. In the case of the Acorn SCSI on my A540, this unit is 1Kb.
- Hence, on average, 512 bytes is wasted at the end of each file − this is
- included in the bytes used returned by *Free, but not by *Count. For the
- 5,134 files on my drive, this totals 2.5Mb.
- 7.2
- Secondly, some space is reserved for each Directory Header. The Index
- occupies 2Kb, irrespective of the drive and filing system which, for my
- 1204 directories, amounts to 2.4Mb, increasing *Count to 24.7Mb.
- However, SCSIFS reserves a larger allocation per directory, as noted by
- several Archive readers, including Steve Drain (Archive 5.12). On the
- A540, each directory is allocated 15Kb, of which only 2Kb is occupied by
- the Index. Some of the rest may, if I am lucky, be occupied by small
- files subsequently created within the directory. If I am unlucky, I lose
- 13Kb per directory. For my 1204 directories, this could amount to
- 15.3Mb.
- 7.2
- Adding this 15.3Mb to the 2.5Mb noted above, gives a maximum wastage of
- 17.8Mb. The actual discrepancy, however, was 42.8 − 24.7 = 18.1Mb, so
- there must have been something I hadn’t discovered. In order to
- investigate, I considered my disc directories in three groups, as
- identified in the table overleaf.
- 7.2
-
- 7.2
- The largest is headed by a directory called Documents. This contains all
- my Impression documents, plus a large number of drawfiles and several
- hundred old First Word Plus text files retained for reference. When I
- discovered the 13Kb per directory wastage, I realised that Impression,
- which normally uses three directories per document, was wasting a great
- deal of space.
- 7.2
- I tackled this problem some time ago, by saving most of my Impression
- documents as Text only. This Impression feature in fact stores the
- Styles with the text, but does not store graphics or frame data. If I
- drag one of the resulting text files onto the Impression icon on the
- iconbar, this displays the text in its original fonts, sizes, etc. If,
- instead, I drag the text of a letter into the document which contains a
- ‘blank’ letterhead, the letter is restored exactly as it was originally
- created − provided it contained no graphics and no frames other than
- those defined in the letterhead document.
- 7.2
- I was thus able to store most of my Impression documents as Text only,
- and recover several megabytes, without losing anything. This was done
- some months ago, before the exercise I am describing here. At that time,
- I also compressed all these ‘document’ files, using Compression and they
- are now read and written using Cfs. Some of the other directories on my
- disc are also held in compressed form and are identified below as Other
- Cfs. The rest (mainly fonts and software) are not compressed and are
- identified as Non-Cfs.
- 7.2
- The table shows the *Count for each group of files and the *Count
- obtained via Cfs, which shows what the count would have been if the
- files had not been compressed. For interest, I have also shown the sizes
- of the backups for each category. These were obtained using by !Backup,
- into a temporary directory on the same disc and noting the *Counts of
- the backup data directories created (excluding the recovery software
- stored with the backup data). !Backup uses !Spark compression which, we
- can see from the figures, has some effect on the Non-Cfs files. For the
- others, however, no further compression is possible and the backup
- actually uses more space than the live files, owing to the directory
- structures and other parameters stored by !Backup.
- 7.2
- In order to assess the Actual Mb used for each group, I copied (by
- dragging) each in turn into a temporary directory on the same disc and
- noted the decrease in *Free bytes. Then I discovered that the three
- figures obtained did not total the Used bytes given by *Free for the
- whole disc − the discrepancy being over 5Mb. After some experimentation,
- I concluded that the copying process did not produce a precise ‘clone’
- occupying the same space as the original. The only way to discover the
- space occupied by a group of directories is to delete it and note the
- increase in *Free bytes.
- 7.2
- Hence I copied each group in turn, then deleted the original, rather
- than the copy, and noted the change in total usage arising from the
- deletion rather than the copying. The copies were then retained in place
- of the originals. This process not only revealed the true original
- sizes, but also gained 5.6Mb free space, because the copies occupied
- less space than the originals!
- 7.2
- Where did this windfall come from? The first point to note is that it
- was all gained in the Documents directories. These have been very active
- in the past. Apart from the usual process of addition and amendment of
- documents, the filing system has also had to endure the process of
- replacing most of the Impression documents with text files, the
- compression of all the files and, recently, a major exercise of
- restructuring the directories and renaming most of the files. Many of
- the recent changes were made by copying files, then deleting the
- originals, rather than by renaming. All this activity must have produced
- considerable small-scale fragmentation of the free space, which is
- perhaps not mapped and included in the *Free bytes. *Compact (which
- should not be needed with this filing system) did produce a
- simplification of the free space *Map, but did not change the number of
- *Free bytes. Copying the files in sequence, however, produces a new
- directory with no fragmented waste.
- 7.2
- As a result of all this, I can now calculate the wasted space as 8.5Kb
- per directory, instead of an apparently impossible 13.3Kb. If I could
- recover all of this, I would save another 10Mb in total, but that seems
- to be impossible. I could recover perhaps three quarters of it by re-
- formatting the disc using a smaller File Allocation, except that I don’t
- want to do that unless it is really necessary, and in any case, I don’t
- appear to have the right Format program ...! Colin Singleton,
- Sheffield.
- 7.2
- • Image enhancement − I think I can offer a solution to Cain Hunt’s
- request for a cheap image enhancer (7.1 p26). With hindsight, I might
- have included the information in the notes on colour printing (7.1 p35).
- Version 0.90 of Acorn’s !ChangeFSI application comes ‘free’ on the RISC
- OS 3.1 Support Disc and its many facilities include most of the sprite
- processing options I suggested; brightening and gamma correction for
- example. It also accepts some foreign formats (e.g. TIFF), converting
- them to sprites.
- 7.2
- The documentation is not so hot. There seems to be nothing between the
- rather sketchy notes starting on page 207 of the RISC OS 3 Applications
- Guide and the detailed but very complex FSIinfo file in the !ChangeFSI
- directory. However, this desktop application is intuitive to use, and
- trial and error will often produce the desired result. Although it is
- possible to apply two or more processing functions in parallel, I do
- support the notes’ recommendation to operate on an unmodified file and
- try changing only one parameter at a time.
- 7.2
- The only process I would like to see added to !ChangeFSI is Chameleon’s
- ‘Weaken’ function which, for me, seems to give more effective control of
- colour sprites than Brighten.
- 7.2
- I spotted a documented facility in !ChangeFSI which allows very large
- output files to be built in ‘strips’ using the parameter ChangeFSI
- <source address><destination address>28-max<n> where n is the desired
- size of the strip, e.g. 512Kb. I wonder if some very clever person might
- be able to use this as a basis for a utility to transfer large
- TIFF files between Archimedes/PCs/Macs, split between two or more MS-DOS
- floppy discs?
- 7.2
- As a further postscript to the colour printing notes, a reader has
- recommended Hewlett Packard HP 92296U transparencies for my Canon LBP-4;
- about 32p each. I’ve since tried them and the results, especially on 600
- dpi graphics, are excellent. Jim Nottingham, York.
- 7.2
- • Indelible ink − At long last, there is an indelible ink refill
- available for HP Deskjet cartridges. They are available from Misco
- Computer Supplies, Faraday Close, Park Farm Industrial Estate,
- Wellingborough, NN8 6XH. A two-refill kits costs £13 plus postage. Mike
- King, Guernsey. A
-