Wireless Application Protocol Bitmap Format

Wireless Bitmap

Filename extension	.wbmp
Internet media type	image/vnd.wap.wbmp
Developed by	WAP Forum
Type of format	Image file formats

Wireless Application Protocol Bitmap Format (shortened to Wireless Bitmap and with file extension .wbmp) is a monochrome graphics file format optimized for mobile computing devices.

WBMP images are monochrome (black & white) so that the image size is kept to a minimum. A black pixel is denoted by 0 and a white pixel is denoted by 1.

Format of Wireless Bitmap Files

Field name	Field type	Size (in bytes)	Purpose
Type	uintvar	variable	Type of the image, and is 0 for monochrome bitmaps.
Fixed header	byte	1	Reserved. Always 0.
Width	uintvar	variable	Width of the image in pixels.
Height	uintvar	variable	Height of the image in pixels.
Data	byte array	variable	Data bytes arranged in rows – one bit per pixel. A black pixel is denoted by 0 and a white pixel is denoted by 1. Where the row length is not divisible by 8, the row is 0-padded to the byte boundary.

Example of a Wireless bitmap

The 3x3 bitmap:

becomes

Octet 1: 00000000 (WBMP type)

Octet 2: 00000000 (Fixed header)

Octet 3: 00000011 (Width) = 3

Octet 4: 00000011 (Height) = 3

Octet 5-7: 3 bits for data then Padding (8-3=5)

Octet 5: 010 00000 (Row 1)

Octet 6: 101 00000 (Row 2)

Octet 7: 010 00000 (Row 3)

External links

• WAP WAE Specification
• Open Mobile Alliance