Standard Icon Sizes
✓
16×16 pixels - Toolbar, Address bar, Favorites
✓
32×32 pixels - Shortcut icons, Desktop, Explorer
✓
48×48 pixels - Windows Explorer, Start Menu
✓
64×64 pixels - Windows Vista, 7, 8, 10
✓
128×128 pixels - High-resolution displays, macOS
✓
256×256 pixels - Windows 10, macOS, High-DPI displays
✓
512×512 pixels - Google Play Store, macOS apps, App Store, Windows 10/11, High-DPI displays
About Icon Files
ICO files are container files that can include multiple images at different sizes and color depths. A good ICO file should contain multiple sizes for optimal display across different platforms.
ICO File Structure
1
Header (6 bytes)
- First 2 bytes: Reserved (usually 0)
- Next 2 bytes: Type (1 for ICO, 2 for CUR)
- Next 2 bytes: Number of images in the file
2
Directory Entries (16 bytes each)
- Width (1 byte, 0 means 256)
- Height (1 byte, 0 means 256)
- Color count (1 byte, 0 means 256 or more)
- Reserved (1 byte, typically 0)
- Color planes (2 bytes, should be 0 or 1)
- Bits per pixel (2 bytes)
- Size of image data in bytes (4 bytes)
- Offset of image data from beginning of file (4 bytes)
3
Image Data
- BMP format: A standard Windows bitmap without the BMP file header
- PNG format: A complete PNG file with its header
Key Points About ICO Files
•
An ICO file can contain multiple images of different sizes (e.g., 16×16, 32×32, 48×48, etc.)
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Each image in the ICO can be either in BMP or PNG format
•
BMP format was the original format, but doesn't support alpha transparency well
•
PNG format was added later (in Windows Vista) and supports full alpha-channel transparency
•
Modern icons typically use PNG format internally for better transparency
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Each image in an ICO file can have different bit depths (1, 4, 8, 24, or 32 bits per pixel)
•
32-bit images have 24 bits for color and 8 bits for an alpha channel (transparency)
