555/565

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Summary

555 and 565 are used to describe different allocations of bits inside a 16-bit integer representing a pixel, as used in Creatures sprite files such as BLK and C16.

Technical Information

In 555 format, the bits are allocated as follows:

 0123 4567 0123 4567
 -rrr rr-- ---- ---- (bitmask: 0x7C00)
 ---- --gg ggg- ---- (bitmask: 0x3E0)
 ---- ---- ---b bbbb (bitmask: 0x1F)

In 565 format, the bits are allocated as follows:

 0123 4567 0123 4567
 rrrr r--- ---- ---- (bitmask: 0xF800)
 ---- -ggg ggg- ---- (bitmask: 0x7E0)
 ---- ---- ---b bbbb (bitmask: 0x1F)

The following macros can be used in C or C++ to decode these values to normal 24-bit format:


/* Decoding macros by bd_ aka bdonlan. I release these into the public domain. */

#define RGB(r, g, b) ((r) << 16 | (g) << 8 | (b))

#define DECODE_555(v)           \
	(RGB(                      \
		  ((uint32_t)(v) & 0x7c00) >> 7,  \
		  ((uint32_t)(v) & 0x03e0) >> 2,  \
		  ((uint32_t)(v) & 0x001f) << 3  \
		 ))

#define DECODE_565(v)           \
	(RGB(                      \
		  ((uint32_t)(v) & 0xf800) >> 8 , \
		  ((uint32_t)(v) & 0x07e0) >> 3 , \
		  ((uint32_t)(v) & 0x001f) << 3   \
		 ))

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