UIImageにブレンドモードを指定して加工する方法

Objective-Cで UIImageにブレンドモードを指定し表示するサンプルを以下に作成しました。

カメラアプリの実験用に Photoshopのように画像を重ねてブレンド表示する方法を色々試しましたので、以下に詳細を記載します。

サンプルダウンロード

https://github.com/masakihirokawa/objc-ui-image-blend-mode

使用する画像

元画像

重ねて表示する画像

結果画像（ブレンドモード: スクリーン）

ブレンドモードの種類

CGBlendMode	説明
kCGBlendModeMultiply	乗算
kCGBlendModeScreen	スクリーン
kCGBlendModeOverlay	オーバーレイ
kCGBlendModeDarken	比較（暗）
kCGBlendModeLighten	比較（明）
kCGBlendModeColorDodge	覆い焼きカラー
kCGBlendModeColorBurn	焼きこみカラー
kCGBlendModeSoftLight	ソフトライト
kCGBlendModeHardLight	ハードライト
kCGBlendModeDifference	差の絶対値
kCGBlendModeExclusion	除外
kCGBlendModeHue	色相
kCGBlendModeSaturation	彩度
kCGBlendModeColor	カラー
kCGBlendModeLuminosity	輝度
kCGBlendModeClear	透明色で描画

ソースコード

ViewController.h

#import <UIKit/UIKit.h>

#define BACK_IMAGE              @"blend_image.png"
#define BACK_IMAGE_WIDTH        640
#define BACK_IMAGE_HEIGHT       1136
#define FRONT_IMAGE             @"Asymmetry_640_1136.jpg"
#define FRONT_IMAGE_WIDTH       640
#define FRONT_IMAGE_HEIGHT      1136
#define FRONT_IMAGE_ALPHA       1.0f
#define PREVIEW_IMAGE_WIDTH     80
#define PREVIEW_IMAGE_HEIGHT    142
#define BLEND_MODE_LABEL_HEIGHT 20

@interface BlendMode : UIView {
@private
    UIImage     *frontImage_;
    UIImage     *backImage_;
    CGBlendMode blendMode_;
}

@property (nonatomic, assign) CGBlendMode blendMode;

- (void)changeMode;

@end

@interface ViewController : UIViewController {
@private
    BlendMode *blendMode_;
    UILabel   *blendModeLabel_;
}

@end

ViewController.m

#import "ViewController.h"

@implementation BlendMode

@synthesize blendMode = blendMode_;

- (id)init
{
    if (self = [super init]) {
        backImage_ = [UIImage imageNamed:BACK_IMAGE];
        frontImage_ = [UIImage imageNamed:FRONT_IMAGE];
        CGRect newFrame = self.frame;
        newFrame.size = frontImage_.size;
        self.frame = newFrame;
    }
    return self;
}

- (void)drawRect:(CGRect)rect
{
    [backImage_ drawInRect:rect];
    [frontImage_ drawInRect:rect blendMode:blendMode_ alpha:FRONT_IMAGE_ALPHA];
}

- (void)changeMode
{
    if (kCGBlendModeLuminosity < ++blendMode_) {
        blendMode_ = kCGBlendModeNormal;
    }
}

@end

#pragma mark private methods definition

@interface ViewController ()

- (void)changeLabel;

@end

#pragma mark start implementation for methods

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    //初期化
    blendMode_ = [[BlendMode alloc] init];
    blendMode_.center = self.view.center;
    blendMode_.autoresizingMask =
        UIViewAutoresizingFlexibleTopMargin |
        UIViewAutoresizingFlexibleBottomMargin;
    [self.view addSubview:blendMode_];

    //重ねて表示するイメージ表示
    UIImage *imageBack = [UIImage imageNamed:BACK_IMAGE];
    UIImageView *imageViewBack = [[UIImageView alloc] initWithImage:imageBack];
    imageViewBack.frame = CGRectMake(0, 0, BACK_IMAGE_WIDTH, BACK_IMAGE_HEIGHT);
    imageViewBack.autoresizingMask =
        UIViewAutoresizingFlexibleLeftMargin |
        UIViewAutoresizingFlexibleRightMargin |
        UIViewAutoresizingFlexibleTopMargin |
        UIViewAutoresizingFlexibleBottomMargin;
    [self.view addSubview:imageViewBack];

    //プレビューイメージ表示
    UIImage *imageFront = [UIImage imageNamed:FRONT_IMAGE];
    UIImageView *imageViewFront = [[UIImageView alloc] initWithImage:imageFront];
    imageViewFront.frame = CGRectMake(320 - PREVIEW_IMAGE_WIDTH,
                                      0,
                                      PREVIEW_IMAGE_WIDTH,
                                      PREVIEW_IMAGE_HEIGHT);
    imageViewFront.autoresizingMask = imageViewFront.autoresizingMask;
    [self.view addSubview:imageViewFront];

    //ブレンドモードを変更するラベル表示
    blendModeLabel_ = [[UILabel alloc] init];
    blendModeLabel_.frame = CGRectMake(0,
                                       self.view.bounds.size.height - BLEND_MODE_LABEL_HEIGHT,
                                       self.view.bounds.size.width,
                                       BLEND_MODE_LABEL_HEIGHT);
    blendModeLabel_.autoresizingMask =
        UIViewAutoresizingFlexibleTopMargin |
        UIViewAutoresizingFlexibleBottomMargin;
    blendModeLabel_.textAlignment = NSTextAlignmentCenter;
    [self.view addSubview:blendModeLabel_];

    //ラベル変更
    [self changeLabel];
}

#pragma mark private methods

- (void)changeLabel {
    switch (blendMode_.blendMode) {
        case kCGBlendModeMultiply:        blendModeLabel_.text = @"kCGBlendModeMultiply"; break;        /* 乗算 */
        case kCGBlendModeScreen:          blendModeLabel_.text = @"kCGBlendModeScreen"; break;          /* スクリーン */
        case kCGBlendModeOverlay:         blendModeLabel_.text = @"kCGBlendModeOverlay"; break;         /* オーバーレイ */
        case kCGBlendModeDarken:          blendModeLabel_.text = @"kCGBlendModeDarken"; break;          /* 比較（暗） */
        case kCGBlendModeLighten:         blendModeLabel_.text = @"kCGBlendModeLighten"; break;         /* 比較（明） */
        case kCGBlendModeColorDodge:      blendModeLabel_.text = @"kCGBlendModeColorDodge"; break;      /* 覆い焼きカラー */
        case kCGBlendModeColorBurn:       blendModeLabel_.text = @"kCGBlendModeColorBurn"; break;       /* 焼きこみカラー */
        case kCGBlendModeSoftLight:       blendModeLabel_.text = @"kCGBlendModeSoftLight"; break;       /* ソフトライト */
        case kCGBlendModeHardLight:       blendModeLabel_.text = @"kCGBlendModeHardLight"; break;       /* ハードライト */
        case kCGBlendModeDifference:      blendModeLabel_.text = @"kCGBlendModeDifference"; break;      /* 差の絶対値 */
        case kCGBlendModeExclusion:       blendModeLabel_.text = @"kCGBlendModeExclusion"; break;       /* 除外 */
        case kCGBlendModeHue:             blendModeLabel_.text = @"kCGBlendModeHue"; break;             /* 色相 */
        case kCGBlendModeSaturation:      blendModeLabel_.text = @"kCGBlendModeSaturation"; break;      /* 彩度 */
        case kCGBlendModeColor:           blendModeLabel_.text = @"kCGBlendModeColor"; break;           /* カラー */
        case kCGBlendModeLuminosity:      blendModeLabel_.text = @"kCGBlendModeLuminosity"; break;      /* 輝度 */
        case kCGBlendModeClear:           blendModeLabel_.text = @"kCGBlendModeClear"; break;           /* 透明色で描画 */
        case kCGBlendModeCopy:            blendModeLabel_.text = @"kCGBlendModeCopy"; break;            /* コピー */
        case kCGBlendModeSourceIn:        blendModeLabel_.text = @"kCGBlendModeSourceIn"; break;
        case kCGBlendModeSourceOut:       blendModeLabel_.text = @"kCGBlendModeSourceOut"; break;
        case kCGBlendModeSourceAtop:      blendModeLabel_.text = @"kCGBlendModeSourceAtop"; break;
        case kCGBlendModeDestinationOver: blendModeLabel_.text = @"kCGBlendModeDestinationOver"; break;
        case kCGBlendModeDestinationIn:   blendModeLabel_.text = @"kCGBlendModeDestinationIn"; break;
        case kCGBlendModeDestinationOut:  blendModeLabel_.text = @"kCGBlendModeDestinationOut"; break;
        case kCGBlendModeDestinationAtop: blendModeLabel_.text = @"kCGBlendModeDestinationAtop"; break;
        case kCGBlendModeXOR:             blendModeLabel_.text = @"kCGBlendModeXOR"; break;
        case kCGBlendModePlusDarker:      blendModeLabel_.text = @"kCGBlendModePlusDarker"; break;
        case kCGBlendModePlusLighter:     blendModeLabel_.text = @"kCGBlendModePlusLighter"; break;
        default:                          blendModeLabel_.text = @"kCGBlendModeNormal"; break;
    }
}

#pragma mark responder

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    //ブレンドモード変更
    [blendMode_ changeMode];

    //ラベルの変更
    [self changeLabel];

    //ブレンド実行
    [blendMode_ setNeedsDisplay];
}

@end