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      1 /* libs/graphics/sgl/SkColor.cpp
      2 **
      3 ** Copyright 2006, The Android Open Source Project
      4 **
      5 ** Licensed under the Apache License, Version 2.0 (the "License");
      6 ** you may not use this file except in compliance with the License.
      7 ** You may obtain a copy of the License at
      8 **
      9 **     http://www.apache.org/licenses/LICENSE-2.0
     10 **
     11 ** Unless required by applicable law or agreed to in writing, software
     12 ** distributed under the License is distributed on an "AS IS" BASIS,
     13 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14 ** See the License for the specific language governing permissions and
     15 ** limitations under the License.
     16 */
     17 
     18 #include "SkColor.h"
     19 #include "SkColorPriv.h"
     20 
     21 SkPMColor SkPreMultiplyARGB(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
     22     if (a != 255) {
     23 #if 0
     24         unsigned scale = SkAlpha255To256(a);
     25         r = SkAlphaMul(r, scale);
     26         g = SkAlphaMul(g, scale);
     27         b = SkAlphaMul(b, scale);
     28 #else
     29         r = SkMulDiv255Round(r, a);
     30         g = SkMulDiv255Round(g, a);
     31         b = SkMulDiv255Round(b, a);
     32 #endif
     33     }
     34     return SkPackARGB32(a, r, g, b);
     35 }
     36 
     37 SkPMColor SkPreMultiplyColor(SkColor c) {
     38     unsigned a = SkColorGetA(c);
     39     unsigned r = SkColorGetR(c);
     40     unsigned g = SkColorGetG(c);
     41     unsigned b = SkColorGetB(c);
     42 
     43     return SkPreMultiplyARGB(a, r, g, b);
     44 }
     45 
     46 //////////////////////////////////////////////////////////////////////////////////////////////
     47 
     48 static inline SkScalar ByteToScalar(U8CPU x) {
     49     SkASSERT(x <= 255);
     50     return SkIntToScalar(x) / 255;
     51 }
     52 
     53 static inline SkScalar ByteDivToScalar(int numer, U8CPU denom) {
     54     // cast to keep the answer signed
     55     return SkIntToScalar(numer) / (int)denom;
     56 }
     57 
     58 void SkRGBToHSV(U8CPU r, U8CPU g, U8CPU b, SkScalar hsv[3]) {
     59     SkASSERT(hsv);
     60 
     61     unsigned min = SkMin32(r, SkMin32(g, b));
     62     unsigned max = SkMax32(r, SkMax32(g, b));
     63     unsigned delta = max - min;
     64 
     65     SkScalar v = ByteToScalar(max);
     66     SkASSERT(v >= 0 && v <= SK_Scalar1);
     67 
     68     if (0 == delta) { // we're a shade of gray
     69         hsv[0] = 0;
     70         hsv[1] = 0;
     71         hsv[2] = v;
     72         return;
     73     }
     74 
     75     SkScalar s = ByteDivToScalar(delta, max);
     76     SkASSERT(s >= 0 && s <= SK_Scalar1);
     77 
     78     SkScalar h;
     79     if (r == max) {
     80         h = ByteDivToScalar(g - b, delta);
     81     } else if (g == max) {
     82         h = SkIntToScalar(2) + ByteDivToScalar(b - r, delta);
     83     } else { // b == max
     84         h = SkIntToScalar(4) + ByteDivToScalar(r - g, delta);
     85     }
     86 
     87     h *= 60;
     88     if (h < 0) {
     89         h += SkIntToScalar(360);
     90     }
     91     SkASSERT(h >= 0 && h < SkIntToScalar(360));
     92 
     93     hsv[0] = h;
     94     hsv[1] = s;
     95     hsv[2] = v;
     96 }
     97 
     98 static inline U8CPU UnitScalarToByte(SkScalar x) {
     99     if (x < 0) {
    100         return 0;
    101     }
    102     if (x >= SK_Scalar1) {
    103         return 255;
    104     }
    105     return SkScalarToFixed(x) >> 8;
    106 }
    107 
    108 SkColor SkHSVToColor(U8CPU a, const SkScalar hsv[3]) {
    109     SkASSERT(hsv);
    110 
    111     U8CPU s = UnitScalarToByte(hsv[1]);
    112     U8CPU v = UnitScalarToByte(hsv[2]);
    113 
    114     if (0 == s) { // shade of gray
    115         return SkColorSetARGB(a, v, v, v);
    116     }
    117     SkFixed hx = (hsv[0] < 0 || hsv[0] >= SkIntToScalar(360)) ? 0 : SkScalarToFixed(hsv[0]/60);
    118     SkFixed f = hx & 0xFFFF;
    119 
    120     unsigned v_scale = SkAlpha255To256(v);
    121     unsigned p = SkAlphaMul(255 - s, v_scale);
    122     unsigned q = SkAlphaMul(255 - (s * f >> 16), v_scale);
    123     unsigned t = SkAlphaMul(255 - (s * (SK_Fixed1 - f) >> 16), v_scale);
    124 
    125     unsigned r, g, b;
    126 
    127     SkASSERT((unsigned)(hx >> 16) < 6);
    128     switch (hx >> 16) {
    129         case 0: r = v; g = t; b = p; break;
    130         case 1: r = q; g = v; b = p; break;
    131         case 2: r = p; g = v; b = t; break;
    132         case 3: r = p; g = q; b = v; break;
    133         case 4: r = t;  g = p; b = v; break;
    134         default: r = v; g = p; b = q; break;
    135     }
    136     return SkColorSetARGB(a, r, g, b);
    137 }
    138 
    139