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quadblitter: trilerp on induction #667

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nick black 2020-06-03 17:35:33 -04:00
parent a8beaf8e56
commit 0b06fa5cd4
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GPG Key ID: 5F43400C21CBFACC
1 changed files with 17 additions and 2 deletions
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19
src/lib/blit.c
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@ -13,6 +13,20 @@ lerp(uint32_t c0, uint32_t c1){
return ret;
}
// linearly interpolate a 24-bit RGB value along each 8-bit channel
static inline uint32_t
trilerp(uint32_t c0, uint32_t c1, uint32_t c2){
uint32_t ret = 0;
unsigned r0, g0, b0, r1, g1, b1, r2, g2, b2;
channel_rgb(c0, &r0, &g0, &b0);
channel_rgb(c1, &r1, &g1, &b1);
channel_rgb(c2, &r2, &g2, &b2);
channel_set_rgb(&ret, (r0 + r1 + r2 + 2) / 3,
(g0 + g1 + g2 + 2) / 3,
(b0 + b1 + b2 + 2) / 3);
return ret;
}
// alpha comes to us 0--255, but we have only 3 alpha values to map them to.
// settled on experimentally.
static inline bool
@ -234,14 +248,15 @@ quadrant_solver(uint32_t tl, uint32_t tr, uint32_t bl, uint32_t br,
diffs[1] = rgb_diff(r0, g0, b0, roth, goth, both);
diffs[2] = rgb_diff(r1, g1, b1, rlerp, glerp, blerp);
diffs[3] = rgb_diff(r1, g1, b1, roth, goth, both);
// FIXME pick closer, not first one we find
if(diffs[0] < diffs[1]){
egc = qd->oth0egc;
*back = colors[qd->others[1]];
// FIXME relerp *fore?
*fore = trilerp(colors[qd->pair[0]], colors[qd->pair[1]], colors[qd->others[0]]);
}else if(diffs[2] < diffs[3]){
egc = qd->oth1egc;
*back = colors[qd->others[0]];
// FIXME relerp *fore?
*fore = trilerp(colors[qd->pair[0]], colors[qd->pair[1]], colors[qd->others[1]]);
}
return egc;
}