Deep Dive into the PostScript Language
So, you want to dive deep into PostScript, huh? Well, buckle up, because we’re about to take a trip down memory lane—back to the days when Steve Jobs was young, Xerox ruled the tech world, and printers needed a PhD to print a simple document.
A Brief History of PostScript
PostScript is the reason why your printer doesn’t just spit out garbled nonsense when you send it a PDF. It was created in the early 1980s by Adobe Systems, founded by former Xerox employees John Warnock and Charles Geschke.
Here’s how it all connects:
- Xerox PARC developed much of the technology that led to PostScript, but they famously fumbled the ball (again) and let Adobe run with it.
- Apple and Steve Jobs saw the potential, licensing PostScript for the LaserWriter in 1985—this was the first laser printer to include PostScript.
- Adobe made bank, and PostScript became the industry standard for printing and desktop publishing.
- PDF (Portable Document Format) is basically a direct descendant of PostScript, designed for documents that need to be displayed consistently across devices.
If you want to geek out more, check out:
How PostScript Works
PostScript is a Turing-complete programming language. That’s right! Your printer is basically a tiny computer running a programming language.
It’s a stack-based language, similar to Forth or RPN (Reverse Polish Notation) calculators. Commands (called “operators”) manipulate a stack, meaning order matters.
Example 1: Basic Stack Manipulation
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10and20are pushed onto the stack.addpops them off, adds them, and pushes the result (30) back onto the stack.
Debugging PostScript
PostScript is not the friendliest language to debug, but here’s how you can do it without wasting paper:
1. Use Ghostscript
Ghostscript is your best friend for running and debugging PostScript files on your computer.
Run a PostScript file with:
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2. Debugging with == and print
- “==” prints the top of the stack.
- “print” prints a string.
Example:
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Testing PostScript Files Without Printing
If you don’t want to hear your printer scream in agony while testing, use:
- Ghostscript
- PostScript viewers like GSView or MuPDF
- Converting PostScript to PDF using:
1ps2pdf myfile.ps myfile.pdf
Essential PostScript Commands with Examples
| Command | Description | Example |
|---|---|---|
moveto | Moves the pen to a position | 100 100 moveto |
lineto | Draws a line from the current position | 200 200 lineto |
stroke | Renders the drawn path | stroke |
fill | Fills a shape | fill |
show | Prints text | (Hello!) show |
setlinewidth | Sets line thickness | 5 setlinewidth |
setrgbcolor | Sets color (RGB) | 1 0 0 setrgbcolor (red) |
Example: Drawing a Red Line
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Example: Drawing a Rectangle
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1. Drawing a Circle
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This draws a circle with a radius of 50 centered at (200, 200).
2. Drawing a Triangle
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Simple triangle with three points connected.
3. Rotating an Object
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This rotates a line by 45 degrees.
4. Scaling an Object
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Doubles the size of a line.
5. Setting a Custom Font and Printing Text
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Uses Times-Roman font at 24pt size.
6. Drawing a Star
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Five lines creating a simple star.
7. Creating a Gradient Effect
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Fills a square with a red color.
8. Making a Dashed Line
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Creates a dashed line with a repeating pattern of 4 pixels on, 2 pixels off.
9. Clipping an Area
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Restricts drawing to a clipped square area.
10. Using Loops to Draw Multiple Lines
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Draws five squares in a row using a loop.
Reference Table: PostScript Commands
Here’s a handy cheat sheet:
| Command | Function |
|---|---|
newpath | Starts a new drawing path |
moveto x y | Moves to (x, y) without drawing |
lineto x y | Draws a line to (x, y) |
curveto x1 y1 x2 y2 x3 y3 | Draws a Bézier curve |
closepath | Closes the path (connects back to start) |
stroke | Renders the path as an outline |
fill | Fills the shape |
showpage | Ends the page and prints it |
setrgbcolor r g b | Sets the color |
setlinewidth n | Sets line thickness |
gsave / grestore | Saves/restores graphic state |
For a complete reference: Adobe PostScript Reference
Key Takeaways
- PostScript is a programming language used for printing.
- It’s stack-based, meaning operations work in a last-in, first-out manner.
- It’s the ancestor of PDF, still used in professional printing.
- You can test PostScript without a printer using Ghostscript and viewers.
- It has a ton of commands, but at its core, it’s all about moving pens and drawing shapes.
PostScript vs. HP’s PCL: The Printer Wars
If you’ve ever dealt with printers, you might have heard about PCL (Printer Command Language), which is HP’s answer to PostScript. These two have been battling it out in the printing world for decades.
A Brief History of Postscript vs PCL
- PostScript (Adobe) was introduced in the 1980s and became the standard for high-end professional printing.
- PCL (HP) was developed by Hewlett-Packard in 1984 as a simpler, more efficient alternative to PostScript for personal and office printers.
- The difference? PostScript is device-independent, meaning it produces the same output no matter the printer, while PCL is faster but more hardware-dependent.
Key Differences Between PostScript and PCL
| Feature | PostScript | PCL |
|---|---|---|
| Developer | Adobe | HP |
| Device Independence | Yes | No |
| Complexity | More complex | Simpler |
| Speed | Slower (interpreted language) | Faster (directly understood by printers) |
| Graphics Quality | High precision | Faster but less precise |
| Usage | High-end printing, publishing | General office printing |
Why PostScript Still Matters
Even though PCL is often used in office printers due to speed and simplicity, PostScript remains the king for graphic designers, publishers, and high-quality printing. If you’re printing a complex PDF or a detailed image, PostScript will ensure it looks the same on any printer.
Links
If you just need fast text printing, PCL is great. If you want perfect graphics and consistency, PostScript wins every time.