A file with the .pdi extension represents a 1-bit bitmap image that has been compiled by pdc. This format uses little endian byte order.
| Offset | Type | Detail |
|---|---|---|
0 |
char[12] |
Ident Playdate IMG |
12 |
uint32 |
Flags |
| Bitmask | Detail |
|---|---|
flags & 0x80000000 |
If > 0, the data in this file is compressed |
If the compression flag is set, there's an extra image header after the file header. Everything after this is zlib-compressed.
| Offset | Type | Detail |
|---|---|---|
0 |
uint32 |
Size of image data section when decompressed |
4 |
uint32 |
Image width (in pixels) |
8 |
uint32 |
Image height (in pixels) |
12 |
uint32 |
Unknown/reserved? Seen as 0 |
.pdi image data comprises of a single Image Cell.
The pdi, .pdt and .pft formats store pixels as "cells", where transparent edges are cropped out to save on space.
| Offset | Type | Detail |
|---|---|---|
0 |
uint16 |
Cell clip width (in pixels) |
2 |
uint16 |
Cell clip height (in pixels) |
4 |
uint16 |
Cell stride (bytes per image row) |
6 |
uint16 |
Cell clip left (in pixels) |
8 |
uint16 |
Cell clip right (in pixels) |
10 |
uint16 |
Cell clip top (in pixels) |
12 |
uint16 |
Cell clip bottom (in pixels) |
14 |
uint16 |
Cell bitflags |
| Bitmask | Detail |
|---|---|
flags & 0x3 |
If > 0, cell uses transparency |
Cells contain at least one 1-bit bitmap for black/white color (0 for black and 1 for white). If the transparency flag is set, this will be followed by an additional 1-bit bitmap for the image alpha (0 for transparent and 1 for opaque).
The number of bytes used by a cell bitmap will be equal to stride * clip height. The number of pixels in each row of the cell bitmap will be equal to clip width. Transparent edges are not stored, and must be added back to the cell based on the values given in the cell header.
The final image width will equal clip left + clip width + clip right, likewise the height will equal clip top + clip height + clip bottom,