Image MIME Reference
ICO
Windows Icon (Legacy MIME)
image/x-icon
VS
Sony SR2 Raw Image
image/x-sony-sr2
Sony-SR2
A complete technical comparison of Windows Icon (Legacy MIME) and Sony SR2 Raw Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
ICO wins on browser support
Feature Support
| Feature | ICO | Sony-SR2 |
|---|---|---|
| Transparency (Alpha) | Yes | ✕ No |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | ✕ No | Yes |
| EXIF Metadata | ✕ No | Yes |
| ICC Color Profile | ✕ No | Yes |
Windows Icon (Legacy MIME)
image/x-icon
Extension
.ico
Container
ICO Directory Structure
Compression
Uncompressed (DIB/BMP) / Deflate (Embedded PNG)
Algorithm
NoneDeflate (via PNG)
Color Depth
1-bit, 4-bit, 8-bit, 24-bit (True Color), 32-bit (RGBA)
Developed by
Microsoft Corporation
Released
1985
Magic Bytes
00 00 01 00
Sony SR2 Raw Image
image/x-sony-sr2
Extension
.sr2
Container
TIFF-based (Proprietary)
Compression
Uncompressed / Sony Proprietary Lossless
Algorithm
NoneSony Proprietary Lossless
Color Depth
12-bit (Per Channel)
Developed by
Sony Corporation
Released
2005
Magic Bytes
49 49 2A 00
Browser Support Comparison
| Browser | ICO | Sony-SR2 |
|---|---|---|
Chrome
|
✓ 1
|
✕ |
Firefox
|
✓ 1
|
✕ |
Safari
|
✓ 1
|
✕ |
Edge
|
✓ 12
|
✕ |
IE (Legacy)
|
✓
|
✕ |
ICO
ICO Strengths
- Universally supported by every web browser in existence for website favicons
- Packs multiple resolutions into a single file, eliminating the need to serve different files for the taskbar vs. the desktop
- Modern support for embedded PNGs (since Windows Vista) allows for excellent 32-bit transparency (alpha channels) and drastically reduced file sizes
Limitations
- Internal file structure is convoluted due to decades of legacy cruft, such as the requirement for BMP data to lack a standard file header but double the height property for an archaic XOR/AND mask
- Larger file size compared to a single optimized PNG or SVG, as it literally stores the same image multiple times at different scales
- The MIME type landscape is highly fragmented (x-icon vs. vnd.microsoft.icon), causing occasional caching or strict-MIME validation errors on restrictive servers
Sony-SR2
Sony-SR2 Strengths
- Retains raw, unprocessed sensor data from legacy cameras, allowing modern raw processors to extract vastly superior image quality than what was possible in 2005
- Utilizes a standard TIFF container structure, ensuring that community-maintained open-source decoding libraries (like LibRaw) can easily parse and maintain support for it indefinitely
Limitations
- Completely obsolete format that has not been utilized in a new camera release in over a decade
- MIME detection via magic bytes is unreliable due to TIFF header spoofing, requiring deeper EXIF inspection
- Cannot be natively viewed in web browsers or standard operating system image viewers without specialized decoders
When to choose which format
ICO
Use ICO when…
- Website Favicons (favicon.ico)
- Windows Application Executable Icons (.exe)
- Desktop Shortcut Icons
Sony-SR2
Use Sony-SR2 when…
- Legacy Sony Cyber-shot/Alpha Photography
- Non-destructive Image Post-Processing
- Raw Imaging Archival