Free webp to jpg
EN
Image MIME Reference
Sealed-PNG

SealedMedia Portable Network Graphics

image/vnd.sealed.png
VS

Silicon Graphics Image

image/sgi
SGI

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

Equal browser support

Feature Support

Feature Sealed-PNG SGI
Transparency (Alpha) ✕ No Yes
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 →
Silicon Graphics Image
image/sgi
Extension
.sgi.rgb.rgba.bw.int.inta
Container SGI Image Format
Compression Uncompressed / Lossless (Run-Length Encoding)
Algorithm
RLENone
Color Depth 8-bit, 16-bit (Per Channel)
Developed by Paul Haeberli (Silicon Graphics)
Released 1990
Magic Bytes
01 DA
Full SGI reference →

Browser Support Comparison

Browser Sealed-PNG SGI
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
SGI

SGI Strengths

  • Pioneered multi-channel and 16-bit per channel imaging capabilities required for high-end 1990s visual effects
  • Extremely robust and simple header structure
  • Reliable Run-Length Encoding provided solid lossless compression for flat-shaded 3D renders
Limitations
  • Completely obsolete for modern web and application development
  • Zero native web browser compatibility
  • Largely replaced by TIFF and OpenEXR in modern professional VFX and 3D pipelines

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
SGI
Use SGI when…
  • Legacy 3D Animation & VFX
  • Silicon Graphics IRIX Workflows
  • Historical CGI Archiving

More comparisons

Sealed-PNG vs ACES → SGI vs ACES → Sealed-PNG vs APNG → SGI vs APNG → Sealed-PNG vs AVCI → SGI vs AVCI → Sealed-PNG vs AVCS → SGI vs AVCS → Sealed-PNG vs AVIF → SGI vs AVIF → All comparisons →
Share this comparison