| // Copyright (c) 2012 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 "ui/gfx/color_utils.h" |
| |
| #include <math.h> |
| #if defined(OS_WIN) |
| #include <windows.h> |
| #endif |
| |
| #include <algorithm> |
| |
| #include "base/basictypes.h" |
| #include "base/logging.h" |
| #include "base/numerics/safe_conversions.h" |
| #include "build/build_config.h" |
| #if defined(OS_WIN) |
| #include "skia/ext/skia_utils_win.h" |
| #endif |
| #include "third_party/skia/include/core/SkBitmap.h" |
| |
| namespace color_utils { |
| |
| |
| // Helper functions ----------------------------------------------------------- |
| |
| namespace { |
| |
| int calcHue(double temp1, double temp2, double hue) { |
| if (hue < 0.0) |
| ++hue; |
| else if (hue > 1.0) |
| --hue; |
| |
| double result = temp1; |
| if (hue * 6.0 < 1.0) |
| result = temp1 + (temp2 - temp1) * hue * 6.0; |
| else if (hue * 2.0 < 1.0) |
| result = temp2; |
| else if (hue * 3.0 < 2.0) |
| result = temp1 + (temp2 - temp1) * (2.0 / 3.0 - hue) * 6.0; |
| |
| // Scale the result from 0 - 255 and round off the value. |
| return static_cast<int>(result * 255 + .5); |
| } |
| |
| // Next two functions' formulas from: |
| // http://www.w3.org/TR/WCAG20/#relativeluminancedef |
| // http://www.w3.org/TR/WCAG20/#contrast-ratiodef |
| |
| double ConvertSRGB(double eight_bit_component) { |
| const double component = eight_bit_component / 255.0; |
| return (component <= 0.03928) ? |
| (component / 12.92) : pow((component + 0.055) / 1.055, 2.4); |
| } |
| |
| SkColor LumaInvertColor(SkColor color) { |
| HSL hsl; |
| SkColorToHSL(color, &hsl); |
| hsl.l = 1.0 - hsl.l; |
| return HSLToSkColor(hsl, 255); |
| } |
| |
| double ContrastRatio(double foreground_luminance, double background_luminance) { |
| DCHECK_GE(foreground_luminance, 0.0); |
| DCHECK_GE(background_luminance, 0.0); |
| foreground_luminance += 0.05; |
| background_luminance += 0.05; |
| return (foreground_luminance > background_luminance) ? |
| (foreground_luminance / background_luminance) : |
| (background_luminance / foreground_luminance); |
| } |
| |
| } // namespace |
| |
| |
| // ---------------------------------------------------------------------------- |
| |
| unsigned char GetLuminanceForColor(SkColor color) { |
| return base::saturated_cast<unsigned char>( |
| (0.3 * SkColorGetR(color)) + |
| (0.59 * SkColorGetG(color)) + |
| (0.11 * SkColorGetB(color))); |
| } |
| |
| double RelativeLuminance(SkColor color) { |
| return (0.2126 * ConvertSRGB(SkColorGetR(color))) + |
| (0.7152 * ConvertSRGB(SkColorGetG(color))) + |
| (0.0722 * ConvertSRGB(SkColorGetB(color))); |
| } |
| |
| void SkColorToHSL(SkColor c, HSL* hsl) { |
| double r = static_cast<double>(SkColorGetR(c)) / 255.0; |
| double g = static_cast<double>(SkColorGetG(c)) / 255.0; |
| double b = static_cast<double>(SkColorGetB(c)) / 255.0; |
| double vmax = std::max(std::max(r, g), b); |
| double vmin = std::min(std::min(r, g), b); |
| double delta = vmax - vmin; |
| hsl->l = (vmax + vmin) / 2; |
| if (SkColorGetR(c) == SkColorGetG(c) && SkColorGetR(c) == SkColorGetB(c)) { |
| hsl->h = hsl->s = 0; |
| } else { |
| 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; |
| // We need to compare for the max value because comparing vmax to r, g, or b |
| // can sometimes result in values overflowing registers. |
| if (r >= g && r >= b) |
| hsl->h = db - dg; |
| else if (g >= r && g >= b) |
| hsl->h = (1.0 / 3.0) + dr - db; |
| else // (b >= r && b >= g) |
| hsl->h = (2.0 / 3.0) + dg - dr; |
| |
| if (hsl->h < 0.0) |
| ++hsl->h; |
| else if (hsl->h > 1.0) |
| --hsl->h; |
| |
| hsl->s = delta / ((hsl->l < 0.5) ? (vmax + vmin) : (2 - vmax - vmin)); |
| } |
| } |
| |
| SkColor HSLToSkColor(const HSL& hsl, SkAlpha alpha) { |
| 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) { |
| uint8 light; |
| |
| if (lightness < 0) |
| light = 0; |
| else if (lightness >= 1.0) |
| light = 255; |
| else |
| light = static_cast<uint8>(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; |
| return SkColorSetARGB(alpha, |
| calcHue(temp1, temp2, hue + 1.0 / 3.0), |
| calcHue(temp1, temp2, hue), |
| calcHue(temp1, temp2, hue - 1.0 / 3.0)); |
| } |
| |
| bool IsWithinHSLRange(const HSL& hsl, |
| const HSL& lower_bound, |
| const HSL& upper_bound) { |
| DCHECK(hsl.h >= 0 && hsl.h <= 1) << hsl.h; |
| DCHECK(hsl.s >= 0 && hsl.s <= 1) << hsl.s; |
| DCHECK(hsl.l >= 0 && hsl.l <= 1) << hsl.l; |
| DCHECK(lower_bound.h < 0 || upper_bound.h < 0 || |
| (lower_bound.h <= 1 && upper_bound.h <= lower_bound.h + 1)) |
| << "lower_bound.h: " << lower_bound.h |
| << ", upper_bound.h: " << upper_bound.h; |
| DCHECK(lower_bound.s < 0 || upper_bound.s < 0 || |
| (lower_bound.s <= upper_bound.s && upper_bound.s <= 1)) |
| << "lower_bound.s: " << lower_bound.s |
| << ", upper_bound.s: " << upper_bound.s; |
| DCHECK(lower_bound.l < 0 || upper_bound.l < 0 || |
| (lower_bound.l <= upper_bound.l && upper_bound.l <= 1)) |
| << "lower_bound.l: " << lower_bound.l |
| << ", upper_bound.l: " << upper_bound.l; |
| |
| // If the upper hue is >1, the given hue bounds wrap around at 1. |
| bool matches_hue = upper_bound.h > 1 |
| ? hsl.h >= lower_bound.h || hsl.h <= upper_bound.h - 1 |
| : hsl.h >= lower_bound.h && hsl.h <= upper_bound.h; |
| return (upper_bound.h < 0 || lower_bound.h < 0 || matches_hue) && |
| (upper_bound.s < 0 || lower_bound.s < 0 || |
| (hsl.s >= lower_bound.s && hsl.s <= upper_bound.s)) && |
| (upper_bound.l < 0 || lower_bound.l < 0 || |
| (hsl.l >= lower_bound.l && hsl.l <= upper_bound.l)); |
| } |
| |
| void MakeHSLShiftValid(HSL* hsl) { |
| if (hsl->h < 0 || hsl->h > 1) |
| hsl->h = -1; |
| if (hsl->s < 0 || hsl->s > 1) |
| hsl->s = -1; |
| if (hsl->l < 0 || hsl->l > 1) |
| hsl->l = -1; |
| } |
| |
| SkColor HSLShift(SkColor color, const HSL& shift) { |
| HSL hsl; |
| SkAlpha 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 += (1.0 - hsl.s) * ((shift.s - 0.5) * 2.0); |
| } |
| |
| SkColor result = HSLToSkColor(hsl, alpha); |
| |
| if (shift.l < 0) |
| return result; |
| |
| // Lightness shifts in the style of popular image editors aren't actually |
| // represented in HSL - the L value does have some effect on saturation. |
| 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 += (255.0 - r) * ((shift.l - 0.5) * 2.0); |
| g += (255.0 - g) * ((shift.l - 0.5) * 2.0); |
| 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)); |
| } |
| |
| void BuildLumaHistogram(const SkBitmap& bitmap, int histogram[256]) { |
| DCHECK_EQ(kN32_SkColorType, bitmap.colorType()); |
| |
| SkAutoLockPixels bitmap_lock(bitmap); |
| |
| int pixel_width = bitmap.width(); |
| int pixel_height = bitmap.height(); |
| for (int y = 0; y < pixel_height; ++y) { |
| for (int x = 0; x < pixel_width; ++x) |
| ++histogram[GetLuminanceForColor(bitmap.getColor(x, y))]; |
| } |
| } |
| |
| double CalculateBoringScore(const SkBitmap& bitmap) { |
| if (bitmap.isNull() || bitmap.empty()) |
| return 1.0; |
| int histogram[256] = {0}; |
| BuildLumaHistogram(bitmap, histogram); |
| |
| int color_count = *std::max_element(histogram, histogram + 256); |
| int pixel_count = bitmap.width() * bitmap.height(); |
| return static_cast<double>(color_count) / pixel_count; |
| } |
| |
| SkColor AlphaBlend(SkColor foreground, SkColor background, SkAlpha alpha) { |
| if (alpha == 0) |
| return background; |
| if (alpha == 255) |
| return foreground; |
| |
| int f_alpha = SkColorGetA(foreground); |
| int b_alpha = SkColorGetA(background); |
| |
| double normalizer = (f_alpha * alpha + b_alpha * (255 - alpha)) / 255.0; |
| if (normalizer == 0.0) |
| return SK_ColorTRANSPARENT; |
| |
| double f_weight = f_alpha * alpha / normalizer; |
| double b_weight = b_alpha * (255 - alpha) / normalizer; |
| |
| double r = (SkColorGetR(foreground) * f_weight + |
| SkColorGetR(background) * b_weight) / 255.0; |
| double g = (SkColorGetG(foreground) * f_weight + |
| SkColorGetG(background) * b_weight) / 255.0; |
| double b = (SkColorGetB(foreground) * f_weight + |
| SkColorGetB(background) * b_weight) / 255.0; |
| |
| return SkColorSetARGB(static_cast<int>(normalizer), |
| static_cast<int>(r), |
| static_cast<int>(g), |
| static_cast<int>(b)); |
| } |
| |
| SkColor BlendTowardOppositeLuminance(SkColor color, SkAlpha alpha) { |
| unsigned char background_luminance = |
| color_utils::GetLuminanceForColor(color); |
| const SkColor blend_color = |
| (background_luminance < 128) ? SK_ColorWHITE : SK_ColorBLACK; |
| return color_utils::AlphaBlend(blend_color, color, alpha); |
| } |
| |
| SkColor GetReadableColor(SkColor foreground, SkColor background) { |
| const SkColor foreground2 = LumaInvertColor(foreground); |
| const double background_luminance = RelativeLuminance(background); |
| return (ContrastRatio(RelativeLuminance(foreground), background_luminance) >= |
| ContrastRatio(RelativeLuminance(foreground2), background_luminance)) ? |
| foreground : foreground2; |
| } |
| |
| SkColor InvertColor(SkColor color) { |
| return SkColorSetARGB( |
| SkColorGetA(color), |
| 255 - SkColorGetR(color), |
| 255 - SkColorGetG(color), |
| 255 - SkColorGetB(color)); |
| } |
| |
| SkColor GetSysSkColor(int which) { |
| #if defined(OS_WIN) |
| return skia::COLORREFToSkColor(GetSysColor(which)); |
| #else |
| NOTIMPLEMENTED(); |
| return SK_ColorLTGRAY; |
| #endif |
| } |
| |
| } // namespace color_utils |