| 1 |
{ |
| 2 |
Calculation of 2d picture coordinates. |
| 3 |
Picture is projected onto xy plane with lower left corner at origin. |
| 4 |
|
| 5 |
A1 - Ratio of height to width for tiles. |
| 6 |
A2 - Average red value for fadered or grey for fadegrey |
| 7 |
A3 - Average green value for fadegreen |
| 8 |
A4 - Average blue value for fadeblue |
| 9 |
A2, A3, A4 - Chroma key color for mixpict |
| 10 |
} |
| 11 |
{ straight coordinates } |
| 12 |
pic_u = Px; |
| 13 |
pic_v = Py; |
| 14 |
{ picture aspect ratio } |
| 15 |
pic_aspect = if(arg(0)-.5, arg(1), 1); |
| 16 |
{ compute borders for mixture } |
| 17 |
inpic = if(and(pic_u, and(pic_v, |
| 18 |
if(pic_aspect-1, and(1-pic_u,pic_aspect-pic_v), |
| 19 |
and(1/pic_aspect-pic_u,1-pic_v) ) ) ), 1, 0); |
| 20 |
{ chroma-key mixing } |
| 21 |
chroma_sum`P = A2 + A3 + A4; |
| 22 |
chroma_tol`P = 0.02 * chroma_sum`P; |
| 23 |
intol`P(a,b) : and(a-b+chroma_tol`P, b-a+chroma_tol`P); |
| 24 |
ischroma`P(r,g,s) = if(FTINY-chroma_sum`P, .001-s, |
| 25 |
if(.001-s, -1, |
| 26 |
and(intol`P(r*chroma_sum`P,A2*s),intol`P(g*chroma_sum`P,A3*s)) |
| 27 |
) ); |
| 28 |
infore(r,g,b) = if(inpic-.5, if(ischroma`P(r,g,r+g+b), 0, 1), 0); |
| 29 |
{ standard tiling } |
| 30 |
tile_u = mod(pic_u,max(1,1/pic_aspect)); |
| 31 |
tile_v = mod(pic_v,max(1,pic_aspect)); |
| 32 |
{ tiling with inversion matching } |
| 33 |
match_u = tri(pic_u,max(1,1/pic_aspect)); |
| 34 |
match_v = tri(pic_v,max(1,pic_aspect)); |
| 35 |
{ brick-type staggering } |
| 36 |
stag_u = if(pic_aspect-1, |
| 37 |
frac(if(frac(pic_v/pic_aspect/2)-.5,pic_u,pic_u+.5)), |
| 38 |
mod(if(frac(pic_v/2)-.5,pic_u,pic_u+.5/pic_aspect), |
| 39 |
1/pic_aspect)); |
| 40 |
stag_v = tile_v; |
| 41 |
{ fade colors for distant viewing } |
| 42 |
fadered(r,g,b) = fade(r, A2, T*.1); |
| 43 |
fadegreen(r,g,b) = fade(g, A3, T*.1); |
| 44 |
fadeblue(r,g,b) = fade(b, A4, T*.1); |
| 45 |
fadegrey(r,g,b) = fade(grey(r,g,b), A2, T*.1); |
