PostScript Level 3

1. PostScript Level 3

Advanced features and optimizations released in 1997, adding better color management, improved imaging, and enhanced performance.

2. Overview

PostScript Level 3 builds on Level 2 with enhanced color management, smoother shading, improved font handling, and better performance. It maintains full backward compatibility with Levels 1 and 2.

3. Key Enhancements

3.1. Color Management

ICC-Based Color: Industry-standard color profiles
Device-Independent Color: Accurate color across devices
CIE-Based Color Spaces: Lab, XYZ color specifications
Rendering Intents: Perceptual, colorimetric, saturation
Color Conversion: Automatic color space conversion

3.2. Advanced Graphics

Smooth Shading: Gradient fills with smooth transitions
Shading Patterns: Type 2 and Type 3 patterns
Improved Transparency: Better blending modes
Anti-aliasing: Smoother rendering of shapes and text
Clipping: Enhanced clipping operations

3.3. Font Improvements

CID-Keyed Fonts: Better Asian language support
Font Subsetting: Embed only used characters
Font Downloading: Improved incremental downloading
OpenType Support: Enhanced font format compatibility

3.4. Performance Enhancements

In-RIP Separations: Device-side color separation
Page Independence: Parallel page processing
Improved Caching: Better resource utilization
Binary Object Sequences: Faster data transmission
Optimized Operators: Performance-tuned operations

3.5. New Features

Masked Images: Alpha channel support
Image Interpolation: Smoother image scaling
In-line Images: Embedded image data
DeviceN Color: Multi-channel spot colors
Trapping: Automatic color trapping

4. New Operators

Level 3 added numerous operators, including:

shfill - Smooth shading fills
setsmoothness - Control rendering quality
setblackgeneration, setundercolorremoval - Color control
sethalftone improvements - Better screening
Image masking operators
DeviceN color operators
Trapping operators
And many more…

5. Device Features

5.1. Page Device Enhancements

Duplex Printing: Two-sided output control
Collation: Automatic page ordering
Media Selection: Paper size and type
Output Management: Advanced job control
Device-Specific Features: Manufacturer extensions

5.2. Imaging Features

Resolution Independence: Scale without quality loss
Spot Color Support: Multiple ink channels
Overprint Control: Precise ink layering
Halftone Screens: Improved screening algorithms

6. Backward Compatibility

Level 3 maintains complete compatibility:

All Level 1 and 2 operators work unchanged
Existing programs run without modification
New features gracefully degrade on older interpreters
Optional feature detection available

7. Common Use Cases

7.1. High-Quality Color Printing

% ICC-based color workflow
[/ICCBased currentdict /IccProfile get] setcolorspace
0.5 0.3 0.8 setcolor

7.2. Smooth Gradients

% Smooth shading from blue to red
<< /ShadingType 2
   /ColorSpace /DeviceRGB
   /Coords [0 0 100 0]
   /Function << /FunctionType 2
                /Domain [0 1]
                /C0 [0 0 1]  % Blue
                /C1 [1 0 0]  % Red
                /N 1 >>
>> shfill

7.3. Image Masking

% Use one image to mask another
/MaskedImage <<
  /ImageType 3
  /InterLeave 1
  /DataSource imagedata
  /MaskDict maskdict
>> def

8. Performance Tips

Use Smooth Shading - Replace gradient fills with shfill for better performance and quality.

Enable In-RIP Separations - Let the RIP handle color separation for faster processing.

Use Binary Encoding - Binary object sequences are faster than ASCII.

9. Best Practices

Use ICC color profiles for consistent color output
Leverage smooth shading for gradients
Take advantage of font subsetting for smaller files
Use image interpolation for better scaling quality
Enable anti-aliasing for professional output

10. See Also

PostScript Level 1 - Original specification
PostScript Level 2 - Color and composite fonts
Version Comparison - Detailed feature comparison
PostScript Levels Overview
Command Reference