PC File Conversion
Brian Pickard
Part 2 - Graphics Files
In the following I will refer to freeware apps. Since there are many such apps that do similar jobs I will not try to list them all. To find them I suggest a web search such as 'PNG to Sprite conversion' etc. Or look on the Acorn portals such as www.drobe.co.uk or www.iconbar.co.uk.
As many of you are no doubt aware graphics files come in two main types:
Bitmap images generally pixel maps of an image.
Vector Graphics are a file of instructions on how to "draw" an image using lines, curves etc.
Bitmaps
Bitmap images have a set resolution, usually a multiple of 90 dots per inch (dpi) in RISC OS while 96 dpi seems quite common in the PC world. But any resolution is possible.
There are many types of bitmap image file. The most common are BMP (Windows native type), TIFF, PNG, GIF and in with RISC OS the Sprite format. All these are really equivalent and therefore can be converted from one type to another fairly easily. There are several RISC OS freeware programs which will do this, !ChangeFSI being the most well known as it is supplied with all RISC OS machines. As far as I know this will change most PC bitmap formats into Sprites. The one exception that !ChangeFSI won't convert is PNG. Another great app is Creator by John Kortink, this can be found at http://acorn.cybervillage.co.uk/software.stm this will create most PC file formats from a Sprite. This is Shareware and deals mainly with GIF, TIFF, PNG and JPEG as well as some not so common formats.
Probably the most comprehensive converter and image modifier I have come across is DPSS (Dave Pillings Scanner Software) by David Pilling. Even though this is sold with Twain drivers for most SCSI scanners it is more than just a scanning application. It deals with pretty well every format you would wish for and you can scale, resample to different dpi, sharpen, change colour depth etc. I use this and can recommend it. You can buy it from Daves web site at http://pilling.users.netlink.co.uk/software.html (click on the Twain link).
Bitmaps from PC
So, if you receive an image from a PC user look at its file name extension to find what type it is, and then use software to change into a sprite. Remember to set the filetype so that RISC OS apps can accept it. In the following list I have suggested some suitable RISC OS apps to convert the PC file to a Sprite.
BMP (Windows Bitmap)
You can use !ChangeFSI or DPSS
TIF (Tagged Image File Format file)
!ChangeFSI or DPSS
GIF (Graphics Interchange File)
!ChangeFSI or !InterGif
PNG (Portable Network Graphic file)
Use DPSS or find some freeware PNG to Sprite converter
ICO (Windows Icon image)
DPSS or freeware Winicon
MTV (Old format not used much now)
!ChangeFSI or DPSS
PCX (Another less used PC format)
!ChangeFSI or DPSS
JPG or JIFJPEG (image used for photos)
!Paint, !ChangeFSI, DPSS plus many freeware apps.
One point concerning the JPEG format.
This format is used by digital cameras. Many of them add extra info, such as camera settings embedded within the file header. This means !ChangeFSI and other conversion utilities cannot always load and convert the file. To overcome this I use !JClean by David Barrow this is free for non commercial use.
Animated GIFs
GIF images can be stored so that they are displayed as animations in WEB browsers. This means there are more than one image in the file. A nice app called InterGIF by Peter Hartley will produce a sprite file containing all the images. This app will also convert a set of images in a sprite file to an animated GIF file and will read Draw files, sprite files, Replay film files.
Sending Bit images to PC Users
With all the different bit image formats in the PC world which is the best to use when sending an image to the PC user? The answer depends upon the image.
If it is fairly small or is a diagrammatic/cartoon style image then use BMP since all windows apps can read this format. The colour depth can be reduced to 256 colours if the size of the file is a problem (this is where DPSS is useful). The BMP file can be compressed using SPARKFS (use the zip archive option) if it to be sent as an email attachment.
If it is a large image (greater than about 480 x 320 pixels) or it is a photograph use JPEG.
This format uses lossy compression to reduce the filesize. Try and set the quality to about 75 for reasonable results. DO NOT try and zip archive this type of file since it could produce a file greater than the original!
Most Windows Photo re-touching/painting apps will be able to read JPEGs.
Just as an example of conversions I have used a digital camcorder grabbing a single frame (using the PC software). Ported this still to the RiscPC as a GIF. Used DPSS to change it to a sprite. Loaded it into Artworks and added titles/labels etc. Saved it using Paints screengrab facility, (checking in Paint that any unwanted borders are deleted and the image size is the same as the original). Used DPSS to change it to a JPEG. Ported this back to the PC. Loaded it back into the camcorders still library and finally recorded it onto the video tape for the required time.
The results impressed the viewers!
Vector Graphics
These types of image files are not so easy to convert.
RISC OS has always had its own Draw format. Then the superior Artworks format (which can output its designs as a Draw file) was added by Computer Concepts.
The PC world has again a number of formats.
WMF (Windows Meta File)
This is similar to a Drawfile. There are freeware converters for RISC OS such as !WMF->Draw and !Draw->WMF
CGM (Computer Graphics Metafile)
Another vector file Again there are freeware converters (!CGM->Draw)
EPS (Encapsulated PostScript)
!Draw->EPS or !AIEps-Drw
MET (Meta file)
!Draw-Met
DXF (Data eXchnage format)
!Dxf-CGM
SVG (Scalable Vector Graphic)
This type is gaining favour especially for web pages. There aren't many RISC OS converters. You can buy a SVG add on for Artworks, DrawWorks Third Millenium will save a drawfile as a SVG file (as will the Select version of !Draw - ED).
I have found that PC apps do not usually deal with many of the above. The most common seems to be WMF. There are limitations especially if Fonts are used. It is best to convert all your Text in Draw to a Path before any conversion.
The neatest way (but expensive!) is to try and find an application that has a PC version as well as a RISC OS one. The closest I have come across (unless any of you know better!) is to use Artworks on RISC OS and Xara X on the PC.
These two are equivalent and understand both RISC OS Draw and Artworks EPS formats.
One of my PC friends has Xara X so we have been able to swop files over the internet reasonably successfully!
I have found WMF to be the best general vector format to use. But do not be surprised if some text goes missing or certain fills etc. do not work.
The main problem occurs when a sprite image is used within the Draw or Artworks file.
Converters seem to leave this out so the WMF version no longer shows the image.
The only way I have managed to port over a Draw file which contains a sprite is as follows:
- Load the Draw file into Artworks. Convert any text to shapes.
- Export the file as an Artworks EPS file. (add file extension of /eps to file name) Port file onto PC harddrive.
- Run Serifs DrawPlus 3 application on the PC.
- >Select import EPS files and then import the file.
Serifs software can be bought quite cheaply and in fact it has even been on some PC Computer magazine discs. It is quite a good program. DrawPlus 3 states it converts the EPS file to a Metafile. So I tried converting a Draw file to a metafile using freeware !Draw-Met by Keith Sloan but Drawplus 3 would not load it.
Using the PDF format
You can change a RISC OS Drawfile into a PDF file using the free GhostScript package or buy RiScript from Cerilica.
First produce a PostScript printout using the RISC OS Postcript version 2 printer driver. (You use the Save option on the Draw Menu). It is advisable to change any sprite in the Drawfile to 24 bit colour depth.
Once the Drawfile is a PDF file then it can be read on a PC by any Adobe Reader from version 4 onwards. The Adobe reader is free so it's common amongst PC users.
This works fine and is the only reliable way of getting any sprites ported across.
General Rules for Vector Graphics
Try not to include any sprite/bitmaps. If you have to then use the PDF method.
Change all text to a path before converting the drawfile to a PC format.
Invest in Xara X and Artworks (expensive!).
Thats it for this part, I have included a test Drawfile called CMYKTest for you to tryout.
If anyone has any different methods of getting vector files to and from RISC OS and PC machines please let me know.
Next time I will look at Spreadsheets and Database files.
Brian Pickard