44504920 00000004 00F0  012C
DPI      taille   dpi_x dpi_y

/* The chunk identifier DPPV */
#define ID_DPPV    MakeID('D','P','P','V')

typedef LONG LongFrac;
typedef struct ( LongFrac x,y,z; )  LFPoint;
typedef LongFrac  APoint[3];

typedef union {
   LFPoint l;
   APoint  a;
   } UPoint;

/* values taken by variable rotType */
#define ROT_EULER  0
#define ROT_INCR   1

/* Disk record describing Perspective state */

typedef struct {
   WORD     rotType;           /* rotation type */
   WORD     iA, iB, iC;        /* rotation angles (in degrees) */
   LongFrac Depth;             /* perspective depth */
   WORD     uCenter, vCenter;  /* coords of center perspective,
                                * relative to backing bitmap,
                                * in Virtual coords
                                */
   WORD     fixCoord;          /* which coordinate is fixed */
   WORD     angleStep;         /* large angle stepping amount */
   UPoint   grid;              /* gridding spacing in X,Y,Z */
   UPoint   gridReset;         /* where the grid goes on Reset */
   UPoint   gridBrCenter;      /* Brush center when grid was last on,
                                * as reference point
                                */
   UPoint   permBrCenter;      /* Brush center the last time the mouse
                                * button was clicked, a rotation performed,
                                * or motion along "fixed" axis
                                */
   LongFrac rot[3][3];         /* rotation matrix */
   } PerspState;

struct PCHGHeader {
   UWORD Compression;
   UWORD Flags;
   WORD  StartLine;
   UWORD LineCount;
   UWORD MinReg;
   UWORD MaxReg;
   UWORD TreeSize;
   UWORD Reserved;
   ULONG OriginalSize;
};

struct SmallLineChanges {
   UBYTE ChangeCount16;
   UBYTE ChangeCount32;
   UWORD PaletteChange[];
};

struct BigLineChanges {
   UWORD ChangeCount;
   struct BigPaletteChange PaletteChange[];
};

struct BigPaletteChange {
   UWORD Register;
   UBYTE Alpha, Red, Blue, Green;
};

PCHG ::= "PCHG" #{ (struct PCHGHeader) (LINEDATA | COMPLINEDATA) }

COMPLINEDATA ::= { TREE COMPDATA }
TREE ::= { UWORD* }
COMPDATA ::= { ULONG* }

COMPDATA, when unpacked, gives a LINEDATA.

LINEDATA ::= { LINEMASK ((struct SmallLineChanges)* | (struct BigLineChanges)*) }
LINEMASK ::= { ULONG* }

R0 R1 R2 R3 R4 R5 R6 R7 G0 G1 G2 G3 G4 G5 G6 G7 B0 B1 B2 B3 B4 B5 B6 B7

R0 R1 ... R7 G0 ... G7 B0 ... B6 B7 A0 A1 A2 A3 A4 A5 A6 A7

Je0 Je1 Je2 Je3 Je4 Je5 Je6 Je7