typedef struct _TIFFImageIter TIFFImageIter;/* The callback function is called for each "block" of image pixel data after   it has been read from the file and decoded. This image pixel data is in the   buffer pp, and this data represents the image pixels from (x,y) to   (x+w,y+h). It is stored in pixel format, so each pixel contains   img->samplesperpixel consecutive samples each containing img->bitspersample   bits of data. The array pp is ordered in h consecutive rows of w+fromskew   pixels each. */typedef void (*ImageIterTileContigRoutine)    (TIFFImageIter*, void *, uint32, uint32, uint32, uint32, int32,	unsigned char*);#define	DECLAREContigCallbackFunc(name) \static void name(\    TIFFImageIter* img, \    void* user_data, \    uint32 x, uint32 y, \    uint32 w, uint32 h, \    int32 fromskew, \    u_char* pp \)typedef void (*ImageIterTileSeparateRoutine)    (TIFFImageIter*, void *, uint32, uint32, uint32, uint32, int32,	unsigned char*, unsigned char*, unsigned char*, unsigned char*);#define	DECLARESepCallbackFunc(name) \static void name(\    TIFFImageIter* img, \    void* user_data, \    uint32 x, uint32 y, \    uint32 w, uint32 h,\    int32 fromskew, \    u_char* r, u_char* g, u_char* b, u_char* a\)struct _TIFFImageIter {	TIFF*	tif;				/* image handle */	int	stoponerr;			/* stop on read error */	int	isContig;			/* data is packed/separate */	int	alpha;				/* type of alpha data present */	uint32	width;				/* image width */	uint32	height;				/* image height */	uint16	bitspersample;			/* image bits/sample */	uint16	samplesperpixel;		/* image samples/pixel */	uint16	orientation;			/* image orientation */	uint16	photometric;			/* image photometric interp */	uint16*	redcmap;			/* colormap pallete */	uint16*	greencmap;	uint16*	bluecmap;						/* get image data routine */	int	(*get)(TIFFImageIter*, void *udata, uint32, uint32);	union {	    void (*any)(TIFFImageIter*);	    ImageIterTileContigRoutine		contig;	    ImageIterTileSeparateRoutine	separate;	} callback;				/* fn to exec for each block */};