Objective-CのUIColorの使い方15選！初心者がマスターするための完全ガイド

UIColor *redColor = [UIColor redColor];
UIColor *blueColor = [UIColor blueColor];
UIColor *greenColor = [UIColor greenColor];

#import <QuartzCore/QuartzCore.h>

// グラデーションの色を定義
UIColor *color1 = [UIColor redColor];
UIColor *color2 = [UIColor blueColor];
CAGradientLayer *gradientLayer = [CAGradientLayer layer];
gradientLayer.colors = @[(__bridge id)color1.CGColor, (__bridge id)color2.CGColor];
gradientLayer.locations = @[@0.0, @1.0];
gradientLayer.startPoint = CGPointMake(0.5, 0.0);
gradientLayer.endPoint = CGPointMake(0.5, 1.0);
gradientLayer.frame = view.bounds;
[view.layer addSublayer:gradientLayer];

UIColor *originalColor = [UIColor redColor];
CGFloat hue, saturation, brightness, alpha;
[originalColor getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha];

// 明度を50%に変更
UIColor *darkerColor = [UIColor colorWithHue:hue saturation:saturation brightness:brightness * 0.5 alpha:alpha];

// 赤色と青色のインスタンスを作成
UIColor *redColor = [UIColor redColor];
UIColor *blueColor = [UIColor blueColor];

// アルファ値を0.5として青色をブレンド
UIColor *blendedColor = [UIColor colorWithCGColor:CGColorCreateCopyWithAlpha(blueColor.CGColor, 0.5)];

// 結果の色をラベルの背景色としてセット
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
label.backgroundColor = blendedColor;
[self.view addSubview:label];

UIColor *color1 = [UIColor redColor];
UIColor *color2 = [UIColor blueColor];

if ([color1 isEqual:color2]) {
    NSLog(@"色は同じです");
} else {
    NSLog(@"色は異なります");
}

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // ランダムな色を生成するコード
    CGFloat red = arc4random_uniform(256) / 255.0;
    CGFloat green = arc4random_uniform(256) / 255.0;
    CGFloat blue = arc4random_uniform(256) / 255.0;
    UIColor *randomColor = [UIColor colorWithRed:red green:green blue:blue alpha:1.0];

    // ビューの背景色に設定する
    self.view.backgroundColor = randomColor;
}

@end

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    UIColor *baseColor = [UIColor blueColor];
    CGFloat hue, saturation, brightness, alpha;

    if ([baseColor getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha]) {
        brightness += 0.2;  // 明るくする
        if (brightness > 1.0) {
            brightness = 1.0;
        }
        UIColor *newColor = [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:alpha];
        self.view.backgroundColor = newColor;
    }
}

@end

#import <UIKit/UIKit.h>

@interface UIColor (Interpolation)
+ (UIColor *)interpolateFromColor:(UIColor *)fromColor toColor:(UIColor *)toColor withFraction:(float)fraction;
@end

@implementation UIColor (Interpolation)

+ (UIColor *)interpolateFromColor:(UIColor *)fromColor toColor:(UIColor *)toColor withFraction:(float)fraction {
    CGFloat fRed, fGreen, fBlue, fAlpha;
    CGFloat tRed, tGreen, tBlue, tAlpha;
    CGFloat red, green, blue, alpha;

    // 初期色のRGBとAlpha値を取得
    [fromColor getRed:&fRed green:&fGreen blue:&fBlue alpha:&fAlpha];
    // 目標色のRGBとAlpha値を取得
    [toColor getRed:&tRed green:&tGreen blue:&tBlue alpha:&tAlpha];

    // 補完
    red = fRed + fraction * (tRed - fRed);
    green = fGreen + fraction * (tGreen - fGreen);
    blue = fBlue + fraction * (tBlue - fBlue);
    alpha = fAlpha + fraction * (tAlpha - fAlpha);

    return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}

@end

#import <UIKit/UIKit.h>

@interface UIImage (AverageColor)
- (UIColor *)averageColor;
@end

@implementation UIImage (AverageColor)

- (UIColor *)averageColor {
    CGImageRef imageRef = [self CGImage];
    NSUInteger width = CGImageGetWidth(imageRef);
    NSUInteger height = CGImageGetHeight(imageRef);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char *rawData = (unsigned char *) calloc(height * width * 4, sizeof(unsigned char));
    NSUInteger bytesPerPixel = 4;
    NSUInteger bytesPerRow = bytesPerPixel * width;
    NSUInteger bitsPerComponent = 8;
    CGContextRef context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
    CGContextRelease(context);

    long totalRed = 0;
    long totalGreen = 0;
    long totalBlue = 0;

    for (int x = 0; x < width; x++) {
        for (int y = 0; y < height; y++) {
            NSUInteger byteIndex = (bytesPerRow * y) + x * bytesPerPixel;
            totalRed += rawData[byteIndex];
            totalGreen += rawData[byteIndex + 1];
            totalBlue += rawData[byteIndex + 2];
        }
    }

    free(rawData);

    CGFloat avgRed = totalRed / (width * height);
    CGFloat avgGreen = totalGreen / (width * height);
    CGFloat avgBlue = totalBlue / (width * height);

    return [UIColor colorWithRed:avgRed/255.0f green:avgGreen/255.0f blue:avgBlue/255.0f alpha:1];
}

@end

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
@property (weak, nonatomic) IBOutlet UILabel *label;
@property (weak, nonatomic) IBOutlet UISlider *slider;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.slider addTarget:self action:@selector(sliderValueChanged:) forControlEvents:UIControlEventValueChanged];
}

- (void)sliderValueChanged:(UISlider *)sender {
    self.label.backgroundColor = [UIColor colorWithRed:sender.value green:sender.value blue:sender.value alpha:1.0];
}
@end

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
@property (weak, nonatomic) IBOutlet UIImageView *imageView;
@end

@implementation ViewController

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    CGPoint location = [touch locationInView:self.imageView];

    UIColor *colorAtTouchPoint = [self colorAtPixel:location inImage:self.imageView.image];
    NSLog(@"Color at touch point: %@", colorAtTouchPoint);
}

- (UIColor *)colorAtPixel:(CGPoint)point inImage:(UIImage *)image {
    unsigned char pixel[4] = {0};
    CGContextRef context = CGBitmapContextCreate(pixel, 1, 1, 8, 4, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaPremultipliedLast);
    CGContextDrawImage(context, CGRectMake(-point.x, -point.y, image.size.width, image.size.height), image.CGImage);
    CGContextRelease(context);

    CGFloat red = pixel[0] / 255.0f;
    CGFloat green = pixel[1] / 255.0f;
    CGFloat blue = pixel[2] / 255.0f;
    CGFloat alpha = pixel[3] / 255.0f;

    return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}
@end

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController <UIPickerViewDelegate, UIPickerViewDataSource>
@property (nonatomic, strong) UIPickerView *colorPicker;
@property (nonatomic, strong) NSArray *colorsArray;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // 色の配列を作成
    self.colorsArray = @[@"赤", @"緑", @"青", @"黄", @"紫", @"オレンジ"];

    // UIPickerViewのインスタンス化と設定
    self.colorPicker = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 100, self.view.frame.size.width, 200)];
    self.colorPicker.delegate = self;
    self.colorPicker.dataSource = self;
    [self.view addSubview:self.colorPicker];
}

// UIPickerViewの列数を設定
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
    return 1;
}

// UIPickerViewの行数を設定
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    return self.colorsArray.count;
}

// UIPickerViewの各行のタイトルを設定
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    return self.colorsArray[row];
}

@end

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
@property (nonatomic, strong) UIView *colorView;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.colorView = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 200, 200)];
    self.colorView.backgroundColor = [UIColor colorWithDynamicProvider:^UIColor * _Nonnull(UITraitCollection * _Nonnull traitCollection) {
        if (traitCollection.userInterfaceStyle == UIUserInterfaceStyleDark) {
            // ダークモードのときの色
            return [UIColor whiteColor];
        } else {
            // ライトモードのときの色
            return [UIColor blackColor];
        }
    }];
    [self.view addSubview:self.colorView];
}
@end

UILabel *label = [[UILabel alloc] init];
label.backgroundColor = [UIColor lightGrayColor];
label.textColor = [UIColor grayColor];
label.text = @"テキストが読みづらい";

label.backgroundColor = [UIColor whiteColor];
label.textColor = [UIColor blackColor];

UIColor *dynamicBackgroundColor = [UIColor colorWithDynamicProvider:^UIColor *(UITraitCollection *traitCollection) {
    if (traitCollection.userInterfaceStyle == UIUserInterfaceStyleDark) {
        return [UIColor blackColor];
    } else {
        return [UIColor whiteColor];
    }
}];

// RGB値を使用してカスタム色を作成
UIColor *customColor = [UIColor colorWithRed:0.5 green:0.6 blue:0.7 alpha:1.0];

// 既存の色を取得
UIColor *originalColor = [UIColor blueColor];

// 色を20%暗くする
UIColor *darkerColor = [originalColor colorWithAlphaComponent:0.8];