Palm bitmap
Palm bitmap, or Palm BitmapType (also called Palm Pilot Tbmp, Palm Pilot Bitmap, Palm pixmap, etc.), is a native bitmap format of Palm OS. It supports a variety of image types and compression schemes.
It can be found embedded in some Palm file formats, and apparently has also been used by itself as a file format. In a PRC file, resources named "Tbmp", "tAIB", and probably others, use this format.
Contents |
Format details
There can be multiple images in a file. Each image begins with a header. In some cases the header is followed by a color table, or a "DirectInfoType" structure. The pixel data follows.
There are about four different versions of the format. This table summarizes the information in the Palm OS Reference (see the Links section below), and uses some terms defined there. It does not include every detail. "Same" means the field is the same as in the previous version.
Multi-byte numeric fields are big-endian. There is possibly also a little-endian variant of BitmapTypeV3 (version=0x83?), which is not covered here.
Header
| Offs. | BitmapTypeV0 | BitmapTypeV1 | BitmapTypeV2 | BitmapTypeV3 |
|---|---|---|---|---|
| 0 | width<Int16> | same | same | same |
| 2 | height<Int16> | same | same | same |
| 4 | rowBytes<UInt16> | same | same | same |
| 6 | flags<BitmapFlagsType>: compressed [unset=uncompressed, set=ScanLine] | flags: compressed [unset=uncompressed, set=ScanLine], hasColorTable | flags: compressed [unset=uncompressed, set=use compressionType field], hasColorTable, hasTransparency, directColor | flags: compressed [unset=uncompressed, set=use compressionType field], hasColorTable, hasTransparency, directColor, noDither |
| 8 | reserved | pixelSize =1,2,4 |
pixelSize =1,2,4,8,16 |
pixelSize =1,2,4,8 |
| 9 | reserved =0 |
version =1 |
version =2 |
version =3 |
| 10 | reserved | nextDepthOffset<UInt16> in 4-byte units |
same | size (header size) |
| 11 | pixelFormat<PixelFormatType> 0=Indexed, 1=565, 2=565LE, 3=IndexedLE | |||
| 12 | reserved | reserved | transparentIndex | unused |
| 13 | compressionType<BitmapCompressionType> 0=ScanLine, 1=RLE, 2=PackBits, 255=None |
same | ||
| 14 | reserved | reserved | reserved | density<DensityType> 72=kDensityLow, 108=kDensityOneAndAHalf, ... |
| 16 | (end of header) | (end of header) | (end of header) | transparentValue<UInt32> |
| 20 | nextBitmapOffset<UInt32> in bytes | |||
| 24 | (additional fields could exist here) |
Specifications
- Palm OS Reference - See "BitmapType" and "BitmapTypeV..." sections starting on p. 518
- Palm Native Image Format
Software
- Netpbm: pnmtopalm, palmtopnm
- ImageMagick (format named "PALM")
