使用CoreImage教程

CoreImage包含有很多实用的滤镜,专业处理图片的库,为了能看到各种渲染效果,请使用如下图片素材.

现在可以开始教程了:

#define FIX_IMAGE(image)  fixImageWidth(image, 320.f)

// 固定图片的宽度

UIImage * fixImageWidth(UIImage *image, CGFloat width)

{

    float newHeight = image.size.height * (width / image.size.width);

    CGSize size = CGSizeMake(width, newHeight);

    UIGraphicsBeginImageContextWithOptions(size, NO, );

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextTranslateCTM(context, 0.0, size.height);

    CGContextScaleCTM(context, 1.0, -1.0);

    CGContextSetBlendMode(context, kCGBlendModeCopy);

    CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, size.width, size.height),

                       image.CGImage);

    UIImage *imageOut = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return imageOut;

}

代码片段

    // 将UIImage转换成CIImage

    CIImage *ciImage = [[CIImage alloc] initWithImage:[UIImage imageNamed:@"1.jpg"]];

    // 创建滤镜

    CIFilter *filter = [CIFilter filterWithName:@"CIPhotoEffectMono"

                                  keysAndValues:kCIInputImageKey, ciImage, nil];

    [filter setDefaults];

    // 获取绘制上下文

    CIContext *context = [CIContext contextWithOptions:nil];

    // 渲染并输出CIImage

    CIImage *outputImage = [filter outputImage];

    // 创建CGImage句柄

    CGImageRef cgImage = [context createCGImage:outputImage

                                       fromRect:[outputImage extent]];

    // 获取图片

    UIImage *showImage = [UIImage imageWithCGImage:cgImage];

    // 释放CGImage句柄

    CGImageRelease(cgImage);

    // 显示图片

    UIImageView *imageView = \

    [[UIImageView alloc] initWithImage:FIX_IMAGE(showImage)];

    [self.view addSubview:imageView];

代码片段

效果如下:

我们对操作进行简易的封装:

CIFilterEffect.h + CIFilterEffect.m

//

//  CIFilterEffect.h

//  CIFilter

//

//  Created by YouXianMing on 14-5-9.

//  Copyright (c) 2014年 Y.X. All rights reserved.

//

#import <Foundation/Foundation.h>

@interface CIFilterEffect : NSObject

@property (nonatomic, strong, readonly) UIImage *result;

- (instancetype)initWithImage:(UIImage *)image filterName:(NSString *)name;

@end

//

//  CIFilterEffect.m

//  CIFilter

//

//  Created by YouXianMing on 14-5-9.

//  Copyright (c) 2014年 Y.X. All rights reserved.

//

#import "CIFilterEffect.h"

@interface CIFilterEffect ()

@property (nonatomic, strong, readwrite) UIImage *result;

@end

@implementation CIFilterEffect

- (instancetype)initWithImage:(UIImage *)image filterName:(NSString *)name

{

    self = [super init];

    if (self)

    {

        // 将UIImage转换成CIImage

        CIImage *ciImage = [[CIImage alloc] initWithImage:image];

        // 创建滤镜

        CIFilter *filter = [CIFilter filterWithName:name

                                      keysAndValues:kCIInputImageKey, ciImage, nil];

        [filter setDefaults];

        // 获取绘制上下文

        CIContext *context = [CIContext contextWithOptions:nil];

        // 渲染并输出CIImage

        CIImage *outputImage = [filter outputImage];

        // 创建CGImage句柄

        CGImageRef cgImage = [context createCGImage:outputImage

                                           fromRect:[outputImage extent]];

        _result = [UIImage imageWithCGImage:cgImage];

        // 释放CGImage句柄

        CGImageRelease(cgImage);

    }

    return self;

}

@end

我们来开始尝试其他的滤镜效果,我们可以尝试的至少有这些:

@"CILinearToSRGBToneCurve",
@"CIPhotoEffectChrome",
@"CIPhotoEffectFade",
@"CIPhotoEffectInstant",
@"CIPhotoEffectMono",
@"CIPhotoEffectNoir",
@"CIPhotoEffectProcess",
@"CIPhotoEffectTonal",
@"CIPhotoEffectTransfer",
@"CISRGBToneCurveToLinear",
@"CIVignetteEffect",