Free webp to jpg
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Image MIME Reference
Sealed-PNG

SealedMedia Portable Network Graphics

image/vnd.sealed.png
VS

AutoCAD Slide

image/vnd.sld
SLD

A complete technical comparison of SealedMedia Portable Network Graphics and AutoCAD Slide — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature Sealed-PNG SLD
Transparency (Alpha) ✕ No ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support ✕ No ✕ No
EXIF Metadata ✕ No ✕ No
ICC Color Profile ✕ No ✕ No
SealedMedia Portable Network Graphics
image/vnd.sealed.png
Extension
.spng.sealed-png
Container SealedMedia / Oracle IRM Wrapper
Compression Encrypted Payload (Deflate)
Algorithm
AES EncryptionDeflate (Internal PNG payload)
Color Depth Encrypted Payload
Developed by SealedMedia (Acquired by Oracle Corporation)
Released Late 1990s / Early 2000s
Magic Bytes
Unknown (Proprietary SealedMedia Container)
Full Sealed-PNG reference →
AutoCAD Slide
image/vnd.sld
Extension
.sld
Container AutoCAD Slide Container
Compression Uncompressed (Vector Instructions)
Algorithm
None
Color Depth 8-bit (AutoCAD Indexed Color)
Developed by Autodesk, Inc.
Released 1980s
Magic Bytes
41 75 74 6F 43 41 44 20 53 6C 69 64 65 0D 0A 1A 00
Full SLD reference →

Browser Support Comparison

Browser Sealed-PNG SLD
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
Sealed-PNG

Sealed-PNG Strengths

  • Provided absolute control over intellectual property, allowing enterprise administrators to instantly revoke viewing rights of a local file globally
  • Detailed audit trails tracked exactly who opened the image, when, and from what IP address
Limitations
  • Completely proprietary and relies on a central authentication server; if the server goes offline, the image is permanently inaccessible
  • No support in modern operating systems, web browsers, or standard image editing software without installing heavy enterprise DRM clients
  • Oracle effectively deprecated the IRM product line, leaving legacy sealed documents difficult to recover
SLD

SLD Strengths

  • Allowed for instantaneous loading of highly complex architectural and engineering blueprints on low-memory MS-DOS systems
  • Easy-to-parse binary structure containing simple opcodes for drawing vectors and polygons
Limitations
  • Completely obsolete and heavily fragmented, largely replaced by PDF and lightweight web-based DXF viewers
  • Destructive 'snapshot' format irrevocably strips all useful, editable CAD geometry data from the original drawing
  • Zero support in web browsers or standard image processing libraries

When to choose which format

Sealed-PNG
Use Sealed-PNG when…
  • Enterprise Information Rights Management (IRM)
  • Secure Corporate Intellectual Property Distribution
  • Revocable Medical or Legal Imaging
SLD
Use SLD when…
  • Legacy AutoCAD Slideshows
  • AutoCAD Custom Icon Menus
  • Historical CAD Archival

More comparisons

Sealed-PNG vs ACES → SLD vs ACES → Sealed-PNG vs APNG → SLD vs APNG → Sealed-PNG vs AVCI → SLD vs AVCI → Sealed-PNG vs AVCS → SLD vs AVCS → Sealed-PNG vs AVIF → SLD vs AVIF → All comparisons →
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