diff options
Diffstat (limited to 'math.c')
| -rw-r--r-- | math.c | 83 |
1 files changed, 83 insertions, 0 deletions
@@ -639,6 +639,13 @@ static v4 rgba_u32_to_v4(u32 rgba) { return V4(c[0], c[1], c[2], c[3]); } +static u32 rgba_v4_to_u32(v4 color) { + return (u32)(color.x * 255) << 24 + | (u32)(color.y * 255) << 16 + | (u32)(color.z * 255) << 8 + | (u32)(color.w * 255); +} + // returns average of red green and blue components of color static float rgba_brightness(u32 color) { u8 r = (u8)(color >> 24), g = (u8)(color >> 16), b = (u8)(color >> 8); @@ -740,3 +747,79 @@ static Rect rect_shrink(Rect r, float amount) { r.size.y = maxf(r.size.y, 0); return r; } + +static v4 color_rgba_to_hsva(v4 rgba) { + float R = rgba.x, G = rgba.y, B = rgba.z, A = rgba.w; + float M = maxf(R, maxf(G, B)); + float m = minf(R, minf(G, B)); + float C = M - m; + float H = 0; + if (C == 0) + H = 0; + if (M == R) + H = fmodf((G - B) / C, 6); + else if (M == G) + H = (B - R) / C + 2; + else if (M == B) + H = (R - G) / C + 4; + H *= 60; + float V = M; + float S = V == 0 ? 0 : C / V; + return V4(H, S, V, A); +} + +static v4 color_hsva_to_rgba(v4 hsva) { + float H = hsva.x, S = hsva.y, V = hsva.z, A = hsva.w; + H /= 60; + float C = S * V; + float X = C * (1 - fabsf(fmodf(H, 2) - 1)); + float R, G, B; + if (H <= 1) + R=C, G=X, B=0; + else if (H <= 2) + R=X, G=C, B=0; + else if (H <= 3) + R=0, G=C, B=X; + else if (H <= 4) + R=0, G=X, B=C; + else if (H <= 5) + R=X, G=0, B=C; + else + R=C, G=0, B=X; + + float m = V-C; + R += m; + G += m; + B += m; + return V4(R, G, B, A); +} + +static u32 color_interpolate(float x, u32 color1, u32 color2) { + x = x * x * (3 - 2*x); // hermite interpolation + + v4 c1 = rgba_u32_to_v4(color1), c2 = rgba_u32_to_v4(color2); + // to make it interpolate more nicely, convert to hsv, interpolate in that space, then convert back + c1 = color_rgba_to_hsva(c1); + c2 = color_rgba_to_hsva(c2); + float h1 = c1.x, s1 = c1.y, v1 = c1.z, a1 = c1.w; + float h2 = c2.x, s2 = c2.y, v2 = c2.z, a2 = c2.w; + + float s_out = lerpf(x, s1, s2); + float v_out = lerpf(x, v1, v2); + float a_out = lerpf(x, a1, a2); + + float h_out; + // because hue is on a circle, we need to make sure we take the shorter route around the circle + if (fabsf(h1 - h2) < 180) { + h_out = lerpf(x, h1, h2); + } else if (h1 > h2) { + h_out = lerpf(x, h1, h2 + 360); + } else { + h_out = lerpf(x, h1 + 360, h2); + } + h_out = fmodf(h_out, 360); + + v4 c_out = V4(h_out, s_out, v_out, a_out); + c_out = color_hsva_to_rgba(c_out); + return rgba_v4_to_u32(c_out); +} |