最近開發一個app，需要大量用到這方面的知識，于是寫了這一個文檔，希望能幫上一些需要查閱的小伙伴，基本上都是代碼片段，沒有什么概念知識。

截取圖片的一部分

    -(UIImage *)getPartOfImage:(UIImage *)img rect:(CGRect)partRect  
    {  
    CGImageRef imageRef = img.CGImage;  
    CGImageRef imagePartRef = CGImageCreateWithImageInRect(imageRef, partRect);  
    UIImage *retImg = [UIImage imageWithCGImage:imagePartRef];  
    CGImageRelease(imagePartRef);  
    return retImg;  
    }  

ios屏幕截圖

普通截圖不能截取通過openGl渲染的視頻,所以截取視頻是不能使用下面的方法的，需要小伙伴自己去尋找其他openGL的截圖方法了

    UIGraphicsBeginImageContextWithOptions(_videoRect.size, YES, 0);     //設置截屏大小
    [[_moviePlayerController.view layer] renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    CGImageRef imageRef = viewImage.CGImage;
    //    CGRect rect = CGRectMake(166, 211, 426, 320);//這里可以設置想要截圖的區域
    CGRect rect = _videoRect;//這里可以設置想要截圖的區域
    CGImageRef imageRefRect =CGImageCreateWithImageInRect(imageRef, rect);
    UIImage *sendImage = [[UIImage alloc] initWithCGImage:imageRefRect];
    UIImageWriteToSavedPhotosAlbum(sendImage, nil, nil, nil);//保存圖片到照片庫
    NSData *imageViewData = UIImagePNGRepresentation(sendImage);
    
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *pictureName= [NSString stringWithFormat:@"screenShow_%d.png",2];
    NSString *savedImagePath = [documentsDirectory stringByAppendingPathComponent:pictureName];
    NSLog(@"截屏路徑打印: %@", savedImagePath);
    
    [imageViewData writeToFile:savedImagePath atomically:YES];//保存照片到沙盒目錄
    CGImageRelease(imageRefRect);

視頻截圖一

ASSet中有兩個方法可以截圖，下面的方法就是其中一個，相比于(視頻截圖二)那個方法,這一個要快得多
但是我不能把控他得很多細節，所以推薦使用(視頻截圖三)

    NSURL *url = [[NSURL alloc] initWithString:[NSString stringWithFormat:@"%@",urlstring]];//initFileURLWithPath:videoURL] autorelease];
    AVURLAsset *urlAsset = [AVURLAsset URLAssetWithURL:url options:nil];
    AVAssetImageGenerator *generator = [AVAssetImageGenerator assetImageGeneratorWithAsset:urlAsset];
    generator.appliesPreferredTrackTransform = NO;
    generator.maximumSize = _videoRect.size;
    NSError *error = nil;
    for (float i = 0; i < second ; i += 0.1) {
    //不會CMTime就去了解一下
    CGImageRef img = [generator copyCGImageAtTime:CMTimeMake(i, 10) actualTime:NULL error:&error];
    UIImage *image = [UIImage imageWithCGImage: img];
    [imageArray addObject:image];
    }

    NSLog(@"iamgeArray = %@",imageArray);
    return imageArray;

視頻截圖二

iOS 9.0之后就不使用下面的方法了，如果大量截圖的話建議不要使用這種方法，很慢，但是有點就是MPMovie中的時間就是我們平時的時間 1 秒對應視頻中得 第1秒、兩秒對應視頻中得第2秒 ...，而且幾句代碼就搞定了

NSMutableArray *imageArray = [NSMutableArray array];
MPMoviePlayerViewController * mpviemController =[[MPMoviePlayerViewController alloc] initWithContentURL:urlstring];
MPMoviePlayerController *mp=[mpviemController moviePlayer];
for (float i = 0; i < second; i += 0.1) {
    UIImage *thumbImage=[mp thumbnailImageAtTime:i timeOption:MPMovieTimeOptionExact];
    //MPMovieTimeOptionExact截取每一幀的圖片，MPMovieTimeOptionNearestKeyFrame關鍵幀
    NSData *imagedata =UIImagePNGRepresentation(thumbImage);
    UIImage *image = [UIImage imageWithData:imagedata];
    [imageArray addObject:image];
}
return imageArray;

視頻截圖三

這是最快捷視頻切圖片的方法，Asset中的最快的方法,使用塊來進行截圖，速度就比其他快上賊多

    //pragma mark    --- 視頻截取
    -(void)cutVideoGetImageArrayWithURl:(NSURL *)urlstring Second:(float)second{
    
    _imageArray = [NSMutableArray array];
    
    
    AVURLAsset *urlAsset = [AVURLAsset URLAssetWithURL:urlstring options:nil];//
    //獲取視頻時長，單位：秒
    AVAssetImageGenerator *generator = [AVAssetImageGenerator assetImageGeneratorWithAsset:urlAsset];
    generator.appliesPreferredTrackTransform = YES;
    generator.maximumSize = _videoRect.size;
    //下面兩句是截取每一幀的關鍵
    generator.requestedTimeToleranceBefore = kCMTimeZero;
    generator.requestedTimeToleranceAfter = kCMTimeZero;
    
    NSMutableArray *timeArray = [NSMutableArray array];
    
    for (int i = 1; i < second * 10 + 1 ; i++) {

    [timeArray addObject:[NSValue valueWithCMTime:CMTimeMake(i * 6, 60)]];
    }
    //開始截圖
    [generator generateCGImagesAsynchronouslyForTimes:timeArray completionHandler:^(CMTime requestedTime, CGImageRef  _Nullable image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError * _Nullable error) {
    UIImage *imageSen = [UIImage imageWithCGImage:image];
    [_imageArray addObject:imageSen];
    }];
    }

以上。