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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 "third_party/skia/include/core/SkColorPriv.h"
#include "third_party/skia/include/effects/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;
}
SkColor HSLToSkColor(U8CPU alpha, HSL hsl) {
double hue = hsl.h;
double saturation = hsl.s;
double lightness = hsl.l;
// If there's no color, we don't care about hue and can do everything based
// on brightness.
if (!saturation) {
U8CPU light;
if (lightness < 0)
light = 0;
else if (lightness >= SK_Scalar1)
light = 255;
else
light = SkDoubleToFixed(lightness) >> 8;
return SkColorSetARGB(alpha, light, light, light);
}
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,
static_cast<int>(rh * 255),
static_cast<int>(gh * 255),
static_cast<int>(bh * 255));
}
void SkColorToHSL(SkColor c, HSL& hsl) {
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.h = h;
hsl.s = s;
hsl.l = l;
}
SkColor HSLShift(SkColor color, HSL shift) {
HSL hsl;
int alpha = SkColorGetA(color);
SkColorToHSL(color, hsl);
// Replace the hue with the tint's hue.
if (shift.h >= 0)
hsl.h = shift.h;
// Change the saturation.
if (shift.s >= 0) {
if (shift.s <= 0.5) {
hsl.s *= shift.s * 2.0;
} else {
hsl.s = hsl.s + (1.0 - hsl.s) *
((shift.s - 0.5) * 2.0);
}
}
SkColor result = HSLToSkColor(alpha, hsl);
// Lightness shifts in the style of popular image editors aren't
// actually represented in HSL - the L value does have some effect
// on saturation.
if (shift.l >= 0) {
double r = static_cast<double>SkColorGetR(result);
double g = static_cast<double>SkColorGetG(result);
double b = static_cast<double>SkColorGetB(result);
if (shift.l <= 0.5) {
r *= (shift.l * 2.0);
g *= (shift.l * 2.0);
b *= (shift.l * 2.0);
} else {
r = (r + (255.0 - r) * ((shift.l - 0.5) * 2.0));
g = (g + (255.0 - g) * ((shift.l - 0.5) * 2.0));
b = (b + (255.0 - b) * ((shift.l - 0.5) * 2.0));
}
return SkColorSetARGB(alpha,
static_cast<int>(r),
static_cast<int>(g),
static_cast<int>(b));
} else {
return result;
}
}
} // namespace skia
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