nscale8x3_video()

LIB8STATIC void nscale8x3_video	(	uint8_t &	r,
		uint8_t &	g,
		uint8_t &	b,
		fract8	scale )

Scale three one-byte values by a fourth one, which is treated as the numerator of a fraction whose demominator is 256.

In other words, it computes r,g,b * (scale / 256), ensuring that non-zero values passed in remain non-zero, no matter how low the scale argument.

Warning

This function always modifies its arguments in place!

Parameters

r	first value to scale
g	second value to scale
b	third value to scale
scale	scale factor, in n/256 units

Definition at line 401 of file scale8.h.

                                              {
#if SCALE8_C == 1
    uint8_t nonzeroscale = (scale != 0) ? 1 : 0;
    r = (r == 0) ? 0 : (((int)r * (int)(scale)) >> 8) + nonzeroscale;
    g = (g == 0) ? 0 : (((int)g * (int)(scale)) >> 8) + nonzeroscale;
    b = (b == 0) ? 0 : (((int)b * (int)(scale)) >> 8) + nonzeroscale;
#elif SCALE8_AVRASM == 1
    nscale8_video_LEAVING_R1_DIRTY(r, scale);
    nscale8_video_LEAVING_R1_DIRTY(g, scale);
    nscale8_video_LEAVING_R1_DIRTY(b, scale);
    cleanup_R1();
#else
#error "No implementation for nscale8x3 available."
#endif
}

References cleanup_R1(), LIB8STATIC, nscale8_video_LEAVING_R1_DIRTY(), and scale.

Referenced by fl::ColorFromPaletteExtended().

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