Bitmap resources (PBI)

PBI is the raw bitmap format used for image resources and GBitmap data. The authoritative description is the Doxygen block in fw/applib/graphics/gbitmap_pbi.h; files are produced by tools/bitmapgen.py (shipped in the app SDK) and loaded by gbitmap_init_with_data() in fw/applib/graphics/gbitmap.c. The info_flags bit layout is BitmapInfo in fw/applib/graphics/gtypes.h.

A PBI file is a 12-byte header, then pixel data, then (for palettized formats) the palette. All multi-byte fields are little-endian:

Offset	Field	Type	Notes
0	`row_size_bytes`	`uint16_t`	row stride
2	`info_flags`	`uint16_t`	see below
4	origin	4 bytes	legacy; ignored by the firmware
8	`width`	`uint16_t`
10	`height`	`uint16_t`
12	pixel data		`row_size_bytes × height` bytes
…	palette		ARGB8 entries; palettized formats only

info_flags:

bit 0: heap-allocated flag; always 0 in files
bits 1–3: pixel format (below)
bit 4: palette-heap-allocated flag; always 0 in files
bits 5–11: reserved
bits 12–15: file version, currently 1 (version 0 files are 2.x-era 1-bit bitmaps without a format field)

Pixel formats

Value	Format	Bits/pixel	Row stride
0	`GBitmapFormat1Bit`	1	word-aligned: `((width + 31) / 32) × 4`
1	`GBitmapFormat8Bit`	8	`width`
2	`GBitmapFormat1BitPalette`	1	byte-aligned: `ceil(width / 8)`
3	`GBitmapFormat2BitPalette`	2	byte-aligned: `ceil(width / 4)`
4	`GBitmapFormat4BitPalette`	4	byte-aligned: `ceil(width / 2)`

(GBitmapFormat8BitCircular exists in the firmware for the round framebuffer but never appears in PBI files.)

1Bit: 1 = white, 0 = black; pixels packed LSB-first within each 32-bit word; padding bits are ignored.
8Bit: one GColor8 (ARGB8, 2 bits per channel) byte per pixel.
Palettized: pixels are palette indices, packed MSB-first within each byte. The palette follows the pixel data and holds exactly 2^bpp ARGB8 entries (2, 4 or 16); the SDK tooling reduces images to the smallest bit depth that covers the colors used.

PebbleOS

Bitmap resources (PBI)

Pixel formats