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// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "skia/ext/skia_utils.h"
#include "skia/include/SkColorPriv.h"
#include "SkGradientShader.h"
namespace skia {
SkShader* CreateGradientShader(int start_point,
int end_point,
SkColor start_color,
SkColor end_color) {
SkColor grad_colors[2] = { start_color, end_color};
SkPoint grad_points[2];
grad_points[0].set(SkIntToScalar(0), SkIntToScalar(start_point));
grad_points[1].set(SkIntToScalar(0), SkIntToScalar(end_point));
return SkGradientShader::CreateLinear(
grad_points, grad_colors, NULL, 2, SkShader::kRepeat_TileMode);
}
// Helper function for HSLToSKColor.
static inline double calcHue(double temp1, double temp2, double hueVal) {
if (hueVal < 0.0)
hueVal++;
else if (hueVal > 1.0)
hueVal--;
if (hueVal * 6.0 < 1.0)
return temp1 + (temp2 - temp1) * hueVal * 6.0;
if (hueVal * 2.0 < 1.0)
return temp2;
if (hueVal * 3.0 < 2.0)
return temp1 + (temp2 - temp1) * (2.0 / 3.0 - hueVal) * 6.0;
return temp1;
}
SkPMColor HSLToSKColor(U8CPU alpha, float hsl[3]) {
double hue = SkScalarToDouble(hsl[0]);
double saturation = SkScalarToDouble(hsl[1]);
double lightness = SkScalarToDouble(hsl[2]);
double scaleFactor = 256.0;
// If there's no color, we don't care about hue and can do everything based
// on brightness.
if (!saturation) {
U8CPU lightness;
if (hsl[2] < 0)
lightness = 0;
else if (hsl[2] >= SK_Scalar1)
lightness = 255;
else
lightness = SkScalarToFixed(hsl[2]) >> 8;
unsigned greyValue = SkAlphaMul(lightness, alpha);
return SkColorSetARGB(alpha, greyValue, greyValue, greyValue);
}
double temp2 = (lightness < 0.5) ?
lightness * (1.0 + saturation) :
lightness + saturation - (lightness * saturation);
double temp1 = 2.0 * lightness - temp2;
double rh = calcHue(temp1, temp2, hue + 1.0 / 3.0);
double gh = calcHue(temp1, temp2, hue);
double bh = calcHue(temp1, temp2, hue - 1.0 / 3.0);
return SkColorSetARGB(alpha,
SkAlphaMul(static_cast<int>(rh * scaleFactor), alpha),
SkAlphaMul(static_cast<int>(gh * scaleFactor), alpha),
SkAlphaMul(static_cast<int>(bh * scaleFactor), alpha));
}
void SkColorToHSL(SkPMColor c, float hsl[3]) {
double r = SkColorGetR(c) / 255.0;
double g = SkColorGetG(c) / 255.0;
double b = SkColorGetB(c) / 255.0;
double h, s, l;
double vmax = r > g ? r : g;
vmax = vmax > b ? vmax : b;
double vmin = r < g ? r : g;
vmin = vmin < b ? vmin : b;
double delta = vmax - vmin;
l = (vmax + vmin) / 2;
if (delta == 0) {
h = 0;
s = 0;
} else {
if (l < 0.5)
s = delta / (vmax + vmin);
else
s = delta / (2 - vmax - vmin);
double dr = (((vmax - r) / 6.0) + (delta / 2.0)) / delta;
double dg = (((vmax - g) / 6.0) + (delta / 2.0)) / delta;
double db = (((vmax - b) / 6.0) + (delta / 2.0)) / delta;
if (r == vmax)
h = db - dg;
else if (g == vmax)
h = (1.0 / 3.0) + dr - db;
else if (b == vmax)
h = (2.0 / 3.0) + dg - dr;
if (h < 0) h += 1;
if (h > 1) h -= 1;
}
hsl[0] = h;
hsl[1] = s;
hsl[2] = l;
}
} // namespace skia
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