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use hsv for saturation adjustment
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@brendan-duncan
brendan-duncan committed Jan 8, 2025
1 parent 4507990 commit a4124d3
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Showing 2 changed files with 91 additions and 60 deletions.
19 changes: 9 additions & 10 deletions lib/src/filter/adjust_color.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ import 'dart:math';
import '../color/channel.dart';
import '../color/color.dart';
import '../image/image.dart';
import '../util/color_util.dart';
import '../util/math_util.dart';

/// Adjust the color of the [src] image using various color transformations.
Expand Down Expand Up @@ -62,7 +63,6 @@ Image adjustColor(Image src,
}

contrast = contrast?.clamp(0, 2);
saturation = saturation?.clamp(0, 2);
gamma = gamma?.clamp(0, 1000);
exposure = exposure?.clamp(0, 1000);
amount = amount.clamp(0, 1000);
Expand All @@ -71,9 +71,6 @@ Image adjustColor(Image src,
const avgLumR = 0.5;
const avgLumG = 0.5;
const avgLumB = 0.5;
const lumCoeffR = 0.2125;
const lumCoeffG = 0.7154;
const lumCoeffB = 0.0721;

final useBlacksWhitesMids = blacks != null || whites != null || mids != null;
late num br, bg, bb;
Expand All @@ -97,8 +94,6 @@ Image adjustColor(Image src,
mb = 1.0 / (1.0 + 2.0 * (mb - 0.5));
}

final num invSaturation =
saturation != null ? 1.0 - saturation : 0.0;
final num invContrast = contrast != null ? 1.0 - contrast : 0.0;

if (exposure != null) {
Expand All @@ -118,6 +113,8 @@ Image adjustColor(Image src,
hueB = ((sqrt(3.0) * s - c) + 1.0) / 3.0;
}

final hsv = <num>[0.0, 0.0, 0.0];

for (final frame in src.frames) {
for (final p in frame) {
final or = p.rNormalized;
Expand All @@ -142,10 +139,12 @@ Image adjustColor(Image src,
}

if (saturation != null) {
final num lum = r * lumCoeffR + g * lumCoeffG + b * lumCoeffB;
r = lum * invSaturation + r * saturation;
g = lum * invSaturation + g * saturation;
b = lum * invSaturation + b * saturation;
rgbToHsv(r, g, b, hsv);
hsv[1] *= saturation;
hsvToRgb(hsv[0], hsv[1], hsv[2], hsv);
r = hsv[0];
g = hsv[1];
b = hsv[2];
}

if (contrast != null) {
Expand Down
132 changes: 82 additions & 50 deletions lib/src/util/color_util.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,6 @@ import '../color/color_uint32.dart';
import '../color/color_uint4.dart';
import '../color/color_uint8.dart';
import '../color/format.dart';
import 'image_exception.dart';

int uint32ToRed(int c) => c & 0xff;

Expand Down Expand Up @@ -138,10 +137,13 @@ num getLuminanceRgb(num r, num g, num b) => 0.299 * r + 0.587 * g + 0.114 * b;
/// Convert an HSL color to RGB, where h is specified in normalized degrees
/// \[0, 1\] (where 1 is 360-degrees); s and l are in the range \[0, 1\].
/// Returns a list \[r, g, b\] with values in the range \[0, 255\].
List<int> hslToRgb(num hue, num saturation, num lightness) {
void hslToRgb(num hue, num saturation, num lightness, List<int> rgb) {
if (saturation == 0) {
final gray = (lightness * 255.0).toInt();
return [gray, gray, gray];
rgb[0] = gray;
rgb[1] = gray;
rgb[2] = gray;
return;
}

num hue2rgb(num p, num q, num t) {
Expand Down Expand Up @@ -172,63 +174,93 @@ List<int> hslToRgb(num hue, num saturation, num lightness) {
final g = hue2rgb(p, q, hue);
final b = hue2rgb(p, q, hue - 1.0 / 3.0);

return [(r * 255.0).round(), (g * 255.0).round(), (b * 255.0).round()];
rgb[0] = (r * 255.0).round();
rgb[1] = (g * 255.0).round();
rgb[2] = (b * 255.0).round();
}

/// Convert an HSV color to RGB, where h is specified in normalized degrees
/// \[0, 1\] (where 1 is 360-degrees); s and l are in the range \[0, 1\].
/// Returns a list \[r, g, b\] with values in the range \[0, 255\].
List<int> hsvToRgb(num hue, num saturation, num brightness) {
if (saturation == 0) {
final gray = (brightness * 255.0).round();
return [gray, gray, gray];
/// Convert an RGB color to HSV.
void rgbToHsv(num r, num g, num b, List<num> hsv) {
final minCh = min(r, min(g, b));
final maxCh = max(r, max(g, b));
final delta = maxCh - minCh;

if (maxCh == 0 || delta == 0) {
hsv[0] = 0;
hsv[1] = 0;
hsv[2] = 0;
return;
}

final num h = (hue - hue.floor()) * 6.0;
final f = h - h.floor();
final num p = brightness * (1.0 - saturation);
final num q = brightness * (1.0 - saturation * f);
final num t = brightness * (1.0 - (saturation * (1.0 - f)));
num h, s, v;
v = maxCh;
s = delta / maxCh; // s

switch (h.toInt()) {
if (r == maxCh) {
h = (g - b) / delta; // between yellow & magenta
} else if (g == maxCh) {
h = 2 + (b - r) / delta; // between cyan & yellow
} else {
h = 4 + (r - g) / delta; // between magenta & cyan
}
h *= 60; // degrees
if (h < 0) {
h += 360;
}
hsv[0] = h;
hsv[1] = s;
hsv[2] = v;
}

/// Convert an HSV color to RGB, where h is specified in normalized degrees
/// \[0, 1\] (where 1 is 360-degrees); s and l are in the range \[0, 1\].
/// Returns a list \[r, g, b\] with values in the range \[0, 255\].
void hsvToRgb(num h, num s, num v, List<num> rgb) {
if (s == 0) {
rgb[0] = v.clamp(0, 1);
rgb[1] = v.clamp(0, 1);
rgb[2] = v.clamp(0, 1);
return;
}

h /= 60.0;
final i = h.floor();
final f = h - i;
final p = (v * (1 - s)).clamp(0, 1);
final q = (v * (1 - s * f)).clamp(0, 1);
final t = (v * (1 - s * (1 - f))).clamp(0, 1);

switch (i) {
case 0:
return [
(brightness * 255.0).round(),
(t * 255.0).round(),
(p * 255.0).round()
];
rgb[0] = v;
rgb[1] = t;
rgb[2] = p;
return;
case 1:
return [
(q * 255.0).round(),
(brightness * 255.0).round(),
(p * 255.0).round()
];
rgb[0] = q;
rgb[1] = v;
rgb[2] = p;
return;
case 2:
return [
(p * 255.0).round(),
(brightness * 255.0).round(),
(t * 255.0).round()
];
rgb[0] = p;
rgb[1] = v;
rgb[2] = t;
return;
case 3:
return [
(p * 255.0).round(),
(q * 255.0).round(),
(brightness * 255.0).round()
];
rgb[0] = p;
rgb[1] = q;
rgb[2] = v;
return;
case 4:
return [
(t * 255.0).round(),
(p * 255.0).round(),
(brightness * 255.0).round()
];
case 5:
return [
(brightness * 255.0).round(),
(p * 255.0).round(),
(q * 255.0).round()
];
default:
throw ImageException('invalid hue');
rgb[0] = t;
rgb[1] = p;
rgb[2] = v;
return;
default: // case 5
rgb[0] = v;
rgb[1] = p;
rgb[2] = q;
return;
}
}

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