动态将彩色图片动画过渡到黑白图片的BlackAndWhiteView

动态将彩色图片动画过渡到黑白图片的BlackAndWhiteView

效果如下：

BlackAndWhiteView.h 与 BlackAndWhiteView.m

//

//  BlackAndWhiteView.h

//  BlackAndWhiteView

//

//  Created by YouXianMing on 14-10-4.

//  Copyright (c) 2014年 YouXianMing. All rights reserved.

//

#import <UIKit/UIKit.h>

@interface BlackAndWhiteView : UIView

@property (nonatomic)         float    blackAlpha;

@property (nonatomic, strong) UIImage *image;

- (void)startImageProcessing;

@end

//

//  BlackAndWhiteView.m

//  BlackAndWhiteView

//

//  Created by YouXianMing on 14-10-4.

//  Copyright (c) 2014年 YouXianMing. All rights reserved.

//

#import "BlackAndWhiteView.h"

@interface BlackAndWhiteView ()

@property (nonatomic, strong) UIImageView *normalView;

@property (nonatomic, strong) UIImageView *blackView;

@property (nonatomic, strong) UIImage     *blackImage;

@end

@implementation BlackAndWhiteView

- (instancetype)initWithFrame:(CGRect)frame

{

    self = [super initWithFrame:frame];

    if (self) {

        _normalView = [[UIImageView alloc] initWithFrame:self.bounds];

        _blackView  = [[UIImageView alloc] initWithFrame:self.bounds];

        _blackView.alpha = .f;

        [self addSubview:_normalView];

        [self addSubview:_blackView];

    }

    return self;

}

- (void)startImageProcessing

{

    if (_image) {

        _normalView.image = _image;

        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, ), ^{

            if (_blackImage == nil) {

                _blackImage = [self grayScale:_image];

            }

            dispatch_async(dispatch_get_main_queue(), ^{

                _blackView.image = _blackImage;

            });

        });

    }

}

#pragma mark - 私有方法

- (UIImage *)grayScale:(UIImage *)inputImage

{

    int width = inputImage.size.width;

    int height = inputImage.size.height;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();

    CGContextRef context = CGBitmapContextCreate(nil,

                                                 width,

                                                 height,

                                                 , // bits per component

                                                 ,

                                                 colorSpace,

                                                 kCGBitmapByteOrderDefault);

    CGColorSpaceRelease(colorSpace);

    if (context == NULL) {

        return nil;

    }

    CGContextDrawImage(context,

                       CGRectMake(, , width, height), inputImage.CGImage);

    CGImageRef image = CGBitmapContextCreateImage(context);

    UIImage *grayImage = [UIImage imageWithCGImage:image];

    CFRelease(image);

    CGContextRelease(context);

    return grayImage;

}

#pragma mark - 重写setter方法

@synthesize blackAlpha = _blackAlpha;

- (void)setBlackAlpha:(float)blackAlpha

{

    _blackAlpha      = blackAlpha;

    _blackView.alpha = blackAlpha;

}

- (float)blackAlpha

{

    return _blackAlpha;

}

@end

使用的源码：

//

//  ViewController.m

//  BlackAndWhiteView

//

//  Created by YouXianMing on 14-10-4.

//  Copyright (c) 2014年 YouXianMing. All rights reserved.

//

#import "ViewController.h"

#import "BlackAndWhiteView.h"

@interface ViewController ()

@property (nonatomic, strong) BlackAndWhiteView *blackView;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    UIImage *image   = [UIImage imageNamed:@"red.jpg"];

    _blackView = [[BlackAndWhiteView alloc] initWithFrame:CGRectMake(, ,

                                                                     image.size.width,

                                                                     image.size.height)];

    _blackView.image  = image;

    _blackView.center = self.view.center;

    [_blackView startImageProcessing];

    [self.view addSubview:_blackView];

    [self performSelector:@selector(run) withObject:nil afterDelay:];

}

- (void)run

{

    [UIView animateWithDuration: animations:^{

        _blackView.blackAlpha = .f;

    }];

}

@end