在Objective-C程序中修改UIImage

#import <UIKit/UIKit.h>

UIImage *image = [UIImage imageNamed:@"image_name"];

// 修改图片的尺寸
CGSize newSize = CGSizeMake(200, 200);
UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
[image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

// 应用滤镜效果
CIImage *ciImage = [[CIImage alloc] initWithImage:image];
CIFilter *filter = [CIFilter filterWithName:@"CISepiaTone"];
[filter setValue:ciImage forKey:kCIInputImageKey];
[filter setValue:@(0.8) forKey:kCIInputIntensityKey];
CIImage *outputImage = [filter outputImage];
CIContext *context = [CIContext contextWithOptions:nil];
CGImageRef cgImage = [context createCGImage:outputImage fromRect:[outputImage extent]];
UIImage *filteredImage = [UIImage imageWithCGImage:cgImage];
CGImageRelease(cgImage);

// 在UIImageView中显示修改后的图片
UIImageView *imageView = [[UIImageView alloc] initWithImage:newImage];
[self.view addSubview:imageView];

// 保存修改后的图片到相册
UIImageWriteToSavedPhotosAlbum(filteredImage, nil, nil, nil);