1
2/*
3 * Copyright 2006 The Android Open Source Project
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#include "SkColor.h"
11#include "SkColorPriv.h"
12
13SkPMColor SkPreMultiplyARGB(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
14    return SkPremultiplyARGBInline(a, r, g, b);
15}
16
17SkPMColor SkPreMultiplyColor(SkColor c) {
18    return SkPremultiplyARGBInline(SkColorGetA(c), SkColorGetR(c),
19                                   SkColorGetG(c), SkColorGetB(c));
20}
21
22///////////////////////////////////////////////////////////////////////////////
23
24static inline SkScalar ByteToScalar(U8CPU x) {
25    SkASSERT(x <= 255);
26    return SkIntToScalar(x) / 255;
27}
28
29static inline SkScalar ByteDivToScalar(int numer, U8CPU denom) {
30    // cast to keep the answer signed
31    return SkIntToScalar(numer) / (int)denom;
32}
33
34void SkRGBToHSV(U8CPU r, U8CPU g, U8CPU b, SkScalar hsv[3]) {
35    SkASSERT(hsv);
36
37    unsigned min = SkMin32(r, SkMin32(g, b));
38    unsigned max = SkMax32(r, SkMax32(g, b));
39    unsigned delta = max - min;
40
41    SkScalar v = ByteToScalar(max);
42    SkASSERT(v >= 0 && v <= SK_Scalar1);
43
44    if (0 == delta) { // we're a shade of gray
45        hsv[0] = 0;
46        hsv[1] = 0;
47        hsv[2] = v;
48        return;
49    }
50
51    SkScalar s = ByteDivToScalar(delta, max);
52    SkASSERT(s >= 0 && s <= SK_Scalar1);
53
54    SkScalar h;
55    if (r == max) {
56        h = ByteDivToScalar(g - b, delta);
57    } else if (g == max) {
58        h = SkIntToScalar(2) + ByteDivToScalar(b - r, delta);
59    } else { // b == max
60        h = SkIntToScalar(4) + ByteDivToScalar(r - g, delta);
61    }
62
63    h *= 60;
64    if (h < 0) {
65        h += SkIntToScalar(360);
66    }
67    SkASSERT(h >= 0 && h < SkIntToScalar(360));
68
69    hsv[0] = h;
70    hsv[1] = s;
71    hsv[2] = v;
72}
73
74static inline U8CPU UnitScalarToByte(SkScalar x) {
75    if (x < 0) {
76        return 0;
77    }
78    if (x >= SK_Scalar1) {
79        return 255;
80    }
81    return SkScalarToFixed(x) >> 8;
82}
83
84SkColor SkHSVToColor(U8CPU a, const SkScalar hsv[3]) {
85    SkASSERT(hsv);
86
87    U8CPU s = UnitScalarToByte(hsv[1]);
88    U8CPU v = UnitScalarToByte(hsv[2]);
89
90    if (0 == s) { // shade of gray
91        return SkColorSetARGB(a, v, v, v);
92    }
93    SkFixed hx = (hsv[0] < 0 || hsv[0] >= SkIntToScalar(360)) ? 0 : SkScalarToFixed(hsv[0]/60);
94    SkFixed f = hx & 0xFFFF;
95
96    unsigned v_scale = SkAlpha255To256(v);
97    unsigned p = SkAlphaMul(255 - s, v_scale);
98    unsigned q = SkAlphaMul(255 - (s * f >> 16), v_scale);
99    unsigned t = SkAlphaMul(255 - (s * (SK_Fixed1 - f) >> 16), v_scale);
100
101    unsigned r, g, b;
102
103    SkASSERT((unsigned)(hx >> 16) < 6);
104    switch (hx >> 16) {
105        case 0: r = v; g = t; b = p; break;
106        case 1: r = q; g = v; b = p; break;
107        case 2: r = p; g = v; b = t; break;
108        case 3: r = p; g = q; b = v; break;
109        case 4: r = t;  g = p; b = v; break;
110        default: r = v; g = p; b = q; break;
111    }
112    return SkColorSetARGB(a, r, g, b);
113}
114