MacGS-550MacGS-550A port of Aladdin Ghostscript to the Macintosh
Version 5.50 - September 18th, 1998
Ghostscript by L. Peter Deutsch
MacGS-550 & Macintosh drivers by Jeff Schindall
NOTE: There are several serious (and so far unresolved) bugs in this release of MacGS.:
Solution: Never move the console window; or permanently hide the console using the MacGS preferences/settings dialog.
These bugs will be resolved prior to the next release!
Copyright (c) 1998 Aladdin Enterprises, Menlo Park, CA. All rights reserved.
- Very Quick Introduction to Ghostscript
- Unpacking
- Rendering a PostScript File
- Converting a Postscript File to PDF
- Extracting TEXT from a PostScript/PDF File
- Settings
- Using MacGS-550 as a Web Helper Application
- Rendering to a File
- Stopping the Application
- About Rendering
- Preferences
- Building MacGS-550
- Known Bugs
- Credits
- Support
Ghostscript is a PostScript interpreter. PostScript is a language, not a graphic file format. A PostScript file is really a program, not graphical data. The difference is that by looking at a PostScript file you (or an application) cannot easily tell what the file represents. Instead, you must run the file to see what it does. Generally, the result of running a PostScript program is to draw marks on a graphical page. (There are PostScript programs that don't draw anything at all! Some are even distributed as test files with Ghostscript.) This works well for printers but is a bit odd for interactive window systems.
Think of MacGS-550 as a virtual printer: Every time you open a file, asking Ghostscript to run it as a PostScript program, the application creates a new sheet of 'paper' and displays it in a window. You can see the program execute as it places marks on the 'paper' in the window (unless your computer is much faster than mine!) Once the program is done, the page is 'ejected' from the printer. However, the application leaves the window on the screen so you can continue to look at it (and scroll it, save it, etc.). But remember, at this point, the page is out of the printer and Ghostscript can no longer change it. If you want to change some parameter (such as scaling), you must change the parameter and then re-open, and thus re-run, the PostScript file.
Please see the file 'readme' and the files that end in '.doc' in the 'files' folder for more information.
The release consists of the following files:
These files are StuffIt archives. If you do not have a program to expand these, you should get the free StuffIt Expander program from your favorite Macintosh archive.
You will only need macgs-550-src.sit if you are planning on compiling the program yourself. See the chapter "Building It" for more details.
Launch the application. By default, it will show you the Ghostscript console window, where you can see messages to and from Ghostscript. After a few seconds, all initialization will be done and you will see the 'GS' prompt in the console window. You don't actually have to wait for the prompt to begin using the program, anything that needs to wait for the prompt will do so automatically if you do it too early.
The program makes extensive use of Balloon Help. Turn it on and explore!
Choosing 'Open' from the 'File' menu lets you choose any TEXT or EPSF file. When you open a file this way, a new window is created, it is presented to Ghostscript for interpretation. This (usually) results in rendering the first page of the file into the window.
If there are more pages in the file, you will see a small alert box with two buttons: 'Next Page' and 'Interrupt'. Clicking the first will clear the window and let Ghostscript continue on with the next page in the file. Clicking the second asks Ghostscript to cancel processing the rest of the file.
Once a file has been rendered, it stays on the screen. You can resize, scroll it, save it (as a PICT file), copy it (to the clipboard). You can have as many windows open as memory allows.
After opening a document, you may print it by choosing the command 'Print' from the 'File' menu. A "settings" dialog is presented for you to adjust the imaging options. Next, the standard print dialog appears and the user may set the page range or print the entire document. If a page range is selected, then the MacGS make take some time and consume a considerable amount of memory skipping to the pages to be printed.
Choosing 'ps2pdf' from the 'Ghostscript' menu lets you choose any TEXT or EPSF file for pdf distillation. Next you will be prompted for an output file save location. When you open a file this way, a pdf file is created, and the input is presented to Ghostscript for distillation. This (usually) results in the creation of a pdf file. You can also distill to a pdf file by dragging a file to the MacGS-550 icon while holding down the option key.
Once a file has been distilled, the ghostscript command line prompt appears in the console window.
Choosing 'ps2ascii' from the 'Ghostscript' menu lets you choose any TEXT, PDF or EPSF file for text extraction. Next you will be prompted for an output file save location. When you open a file this way, a TEXT file is created.
Once the operation has concluded, the ghostscript command line prompt appears in the console window.
You can change the settings of output media with the "Settings" dialog. Open this dialog by choosing "Settings..." from the "Edit" menu. There are three major sections:
Page Size lets you set the size of the 'logical' page. This is the size that the PostScript file works with.
Scaling lets you enlarge or reduce the 'logical' page to produce the actual output you see. This scaling happens conceptually after the page is printed. However, Ghostscript is aware of this final scaling and will adjust some parameters accordingly (such as halftone screen, or any other parameters that are in 'device coordinates').
Image Options let you select options that pertain to how the image is rendered and recorded.
For example, if you want to render a document that was designed for a Letter size paper, but you want the output to be reduced to half size, then choose "US Letter" for the Page Size and "Half" for the Scaling.
There are too many controls and options in this dialog to discuss here: Turn on balloon help and explore it!
The options apply to all devices (see below), except Image Options which only apply to the 'mac' device.
You can use MacGS-550 as a helper application for your web browser. The following steps show how to configure the Netscape browser. If you are using a different browser, the configuration will be similar:
Some browsers, though not Netscape, may need to be restarted before the change will take effect.
IMPORTANT: Postscript includes operators for manipulating files. A buggy or malicious postscript file could damage the files on your harddisk. To minimize this risk, you should start MacGS-550 and set the command line in the Preferences to:
-dSAFER
This disable a number of file operations in Ghostscript. Note that there are two problems with this: (a) This option does not claim to be fool proof - Postscript is very powerful and this option can't guard against all possible problems. (b) You will be unable to render to any of the file devices when this is set. However, you still be able to save what you render to the screen as PICT files.
To turn off this feature, you need to remove -dSAFER from the command line in the Preferences dialog, then quit and restart MacGS-550.
Ghostscript supports a large number of graphic output formats. Ghostscript calls these devices. When your copy of the Macintosh port of Ghostscript was built, some devices were chosen to be included. Since there are over a hundred devices, generally not all were included. When you run the application, the devices that are included are listed in the 'Devices' menu. The first one is always 'mac', which is the device for rendering into a Macintosh window.
To use another device, and cause Ghostscript to render into a graphic file, choose the device from the Device menu, and then open the file as normal. This time, instead of a new window appearing, you will be asked to named a file to hold the output. The settings dialog can be used to set the page size and scaling options. Note that the image options have no effect on other devices. To switch back to rendering into a window, just choose 'mac' from the 'Devices' menu.
You can attempt to interrupt Ghostscript from whatever it is doing with the <command><period> key sequence (it is also available as 'Interrupt' in the 'Ghostscript' menu). Interrupting a PostScript program is inherently unpredictable. This is because a PostScript file can trap the user-interrupt and refuse to stop! Interrupt is implemented so that it should work smoothly in most cases, but you can't be sure. If it doesn't work, hit it a few more times.
Similarly, Quit is also something that a PostScript program can refuse to do! Sometimes, Ghostscript may not appear not to quit. Always give it a few seconds to try. If it just won't quit, the work around is to type: <option><command><escape> (all at once) to invoke the System 7 Forced Quit dialog.
Ghostscript interprets PostScript programs and renders the graphics that they output. The resulting output image is invariably device dependent. Indeed, the original PostScript file is the device independent form of the image.
Even though the images that Ghostscript renders can be saved in PICT files or on the clipboard in PICT format, these are still device dependent versions of the image: they will not scale well, nor will they display well with different numbers of available colors. These PICT images are simply pixel graphics, not object-oriented graphics. (If you examine these PICT files in a graphics program, you will notice that they are just a single large pixel map.)
The Macintosh device currently renders to any of the following characteristics (which you control in the Settings dialog): 72 dpi 1, 4, or 8 bits per pixel standard Macintosh palettes for 4-bit gray, or 8-bit color
These choices must be made at the time Ghostscript renders an image so that Ghostscript can do its best. For example, Ghostscript will use halftone screens to achieve colors not in the palette.
Though the scaling options may change the dpi from the point of view of the PostScript program, the resulting image on the screen (obviously, as we can't change your hardware on the fly!) and as saved in a PICT file, is 72dpi. For example: If you choose a scaling option of a "Third", the PostScript program appears to render on a 24dpi device, as 24 pixels make up an inch. On the screen, however, 24 pixels make up a third of an inch at 72dpi, thus achieving the 'Third' scaling factor.
The standard Macintosh 8-bit palette is a color cube of 6x6x6 values in RGB space. In addition, it adds evenly spaced ramps of 16 values each of red, green, blue, and gray. Using this palette allows Ghostscript to render with out having the change the palette of a normal 8-bit display system.
There are a number of application settings that can be set with "Preferences" dialog. Open this dialog by choosing "Preferences..." from the "File" menu. There are three major sections:
Command Line lets you choose what the command line is for starting Ghostscript. Generally leaving it empty is fine. You can also choose to have the program ask you each time the program starts.
Windows and Dialogs let you set which windows are shown at start up, and how to handle the Next Page condition. You can choose to have either a sound play or a small dialog appear, or both, when Ghostscript is waiting to display another page.
Remember lets you choose what information is remembered from one invocation of the application to the next.
By default, Ghostscript is started with a blank command line. This can be changed in two ways. First, you can set the command line in the preferences. Second, you can set the preferences to ask you each time the application starts. In this mode, when you start the program, you will see a prompt for command line options in the console window.
Almost everything that can be set on a command line can be set after Ghostscript is running either through the Settings dialog, or by typing into the console window. However, there are few command line options that can be useful:
Do not set either of the first two as part of a default command line in the Preferences dialog, or each time you start it, Mac GS will display the information and quit.
If you want to build the release (so you can configure Ghostscript to your liking), you will need the current Ghostscript release and the macintosh specific files.
From the standard Ghostscript ftp site, obtain the following files:
In the standard method of building Ghostscript, all of these files (except the jpeg) get unpacked into one big directory. The jpeg stuff gets unpacked into a directory called jpeg-6a in the main directory. The macintosh stuff also gets unpacked into its own directory, called 'Mac Specific'. However, if you like (and I do) you can divide up all these files into the following hierarchy:
Once you get everything laid out, take a look at the file Worksheet in the mac specific folder for steps to build the system.
NOTE: There are several serious (and so far unresolved) bugs in this release of MacGS.:
Solution: Never move the console window; or permanently hide the console using the MacGS preferences/settings dialog.
These bugs will be resolved prior to the next release!
Features for future releases that I'm considering (these are in no particular order):
MacGS-550 is written by Jeff Schindall and is based on previous work written by Mark Lentczner of Glyphic Technology. While it is a substantially a new port of Ghostscript to the Macintosh, the previous port by Martin Fong served as inspiration and a starting point.
Ghostscript was created by L. Peter Deutsch of Aladdin Enterprises. Please see the document README in the files directory of the release for more information.
MacGS-550 could not have happend without the faithful help of over fifty beta testers. A tip'o'the mouse to them :)
MacGS-550 is distributed under the Aladdin Ghostscript Free Public License. See the file PUBLIC in the files directory of the relase for the full text. As a piece of free software, neither Aladdin Enterprises nor Glyphic Technology can offer any direct support for it. If you have questions please try the news group comp.lang.postscript, where Ghostscript is discussed.
If you are interested in licensing all or any part of the Ghostscript system, including MacGS-550, please the information in the file README in the files directory of the release.
NOTE: There are several serious (and so far unresolved) bugs in this release of MacGS.:
Solution: Never move the console window; or permanently hide the console using the MacGS preferences/settings dialog.
These bugs will be resolved prior to the next release!