diff options
| -rw-r--r-- | misc.c | 83 |
1 files changed, 66 insertions, 17 deletions
@@ -3,6 +3,7 @@ */ #include <assert.h> +#include <math.h> #include <stdlib.h> #include <string.h> #include <stdio.h> @@ -197,30 +198,78 @@ char *fgetline(FILE *fp) return ret; } +/* Utility functions for colour manipulation. */ + +static float colour_distance(const float a[3], const float b[3]) +{ + return (float)sqrt((a[0]-b[0]) * (a[0]-b[0]) + + (a[1]-b[1]) * (a[1]-b[1]) + + (a[2]-b[2]) * (a[2]-b[2])); +} + +static void colour_mix(const float src1[3], const float src2[3], + float p, float dst[3]) +{ + int i; + for (i = 0; i < 3; i++) + dst[i] = src1[i] * (1.0F - p) + src2[i] * p; +} + void game_mkhighlight_specific(frontend *fe, float *ret, int background, int highlight, int lowlight) { - float max; + static const float black[3] = { 0.0F, 0.0F, 0.0F }; + static const float white[3] = { 1.0F, 1.0F, 1.0F }; + float db, dw; int i; - /* - * Drop the background colour so that the highlight is - * noticeably brighter than it while still being under 1. + * New geometric highlight-generation algorithm: Draw a line from + * the base colour to white. The point K distance along this line + * from the base colour is the highlight colour. Similarly, draw + * a line from the base colour to black. The point on this line + * at a distance K from the base colour is the shadow. If either + * of these colours is imaginary (for reasonable K at most one + * will be), _extrapolate_ the base colour along the same line + * until it's a distance K from white (or black) and start again + * with that as the base colour. + * + * This preserves the hue of the base colour, ensures that of the + * three the base colour is the most saturated, and only ever + * flattens the highlight and shadow to pure white or pure black. + * + * K must be at most sqrt(3)/2, or mid grey would be too close to + * both white and black. Here K is set to sqrt(3)/6 so that this + * code produces the same results as the former code in the common + * case where the background is grey and the highlight saturates + * to white. */ - max = ret[background*3]; - for (i = 1; i < 3; i++) - if (ret[background*3+i] > max) - max = ret[background*3+i]; - if (highlight >= 0 && max * 1.2F > 1.0F) { - for (i = 0; i < 3; i++) - ret[background*3+i] /= (max * 1.2F); + const float k = sqrt(3)/6.0F; + if (lowlight >= 0) { + db = colour_distance(&ret[background*3], black); + if (db < k) { + for (i = 0; i < 3; i++) ret[lowlight*3+i] = black[i]; + if (db == 0.0F) + colour_mix(black, white, k/sqrt(3), &ret[background*3]); + else + colour_mix(black, &ret[background*3], k/db, &ret[background*3]); + } else { + colour_mix(&ret[background*3], black, k/db, &ret[lowlight*3]); + } } - - for (i = 0; i < 3; i++) { - if (highlight >= 0) - ret[highlight * 3 + i] = ret[background * 3 + i] * 1.2F; - if (lowlight >= 0) - ret[lowlight * 3 + i] = ret[background * 3 + i] * 0.8F; + if (highlight >= 0) { + dw = colour_distance(&ret[background*3], white); + if (dw < k) { + for (i = 0; i < 3; i++) ret[highlight*3+i] = white[i]; + if (dw == 0.0F) + colour_mix(white, black, k/sqrt(3), &ret[background*3]); + else + colour_mix(white, &ret[background*3], k/dw, &ret[background*3]); + /* Background has changed; recalculate lowlight. */ + if (lowlight >= 0) + colour_mix(&ret[background*3], black, k/db, &ret[lowlight*3]); + } else { + colour_mix(&ret[background*3], white, k/dw, &ret[highlight*3]); + } } } |