UIImage一些扩展（获取视频第一帧、色值转图片、base64字符串转图片、加载gif图）

下面的都是类方法

pragma mark ---- 获取图片第一帧

• (UIImage*) JJthumbnailImageForVideo:(NSURL *)videoURL atTime:(NSTimeInterval)time {

  AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:videoURL options:nil];
  NSParameterAssert(asset);
  AVAssetImageGenerator *assetImageGenerator =[[AVAssetImageGenerator alloc] initWithAsset:asset];
  assetImageGenerator.appliesPreferredTrackTransform = YES;
  assetImageGenerator.apertureMode = AVAssetImageGeneratorApertureModeEncodedPixels;

  CGImageRef thumbnailImageRef = NULL;
  CFTimeInterval thumbnailImageTime = time;
  NSError thumbnailImageGenerationError = nil;
  thumbnailImageRef = [assetImageGenerator copyCGImageAtTime:CMTimeMake(thumbnailImageTime, 60)actualTime:NULL error:&thumbnailImageGenerationError];
  if(!thumbnailImageRef)
  NSLog(@"thumbnailImageGenerationError %@",thumbnailImageGenerationError);
  UIImagethumbnailImage = thumbnailImageRef ? [[UIImage alloc]initWithCGImage: thumbnailImageRef] : nil;
  return thumbnailImage;
  }

pragma mark ---- 色值转图片

• (UIImage *)imageWithColor:(UIColor *)color withCenter:(UIImage *)centerImage size:(CGSize)size
  {
  UIView *background = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, size.width, size.height)];
  [background setBackgroundColor:color];

  UIImageView *imageView = [[UIImageView alloc] initWithImage:centerImage];
  [background addSubview:imageView];
  imageView.center = background.center;

  // Render image
  UIGraphicsBeginImageContextWithOptions(background.bounds.size, background.opaque, 0.0);
  [background.layer renderInContext:UIGraphicsGetCurrentContext()];

  UIImage * img = UIGraphicsGetImageFromCurrentImageContext();

  UIGraphicsEndImageContext();

  return img;

}

pragma mark ---- base64字符串转图片

• (UIImage *)Base64StrToUIImage:(NSString *)encodedImageStr{
  if (encodedImageStr.length==0) {
  return nil;
  }
  NSData *decodedImageData = [[NSData alloc] initWithBase64EncodedString:encodedImageStr options:NSDataBase64DecodingIgnoreUnknownCharacters];
  UIImage *decodedImage = [UIImage imageWithData:decodedImageData];
  return decodedImage;
  }

pragma mark ---- 加载gif图

• (UIImage *)loadGif_animatedGIFWithData:(NSData *)data {
  if (!data) {
  return nil;
  }

  CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);

  size_t count = CGImageSourceGetCount(source);

  UIImage *animatedImage;

  if (count <= 1) {
  animatedImage = [[UIImage alloc] initWithData:data];
  }
  else {
  NSMutableArray *images = [NSMutableArray array];

    NSTimeInterval duration = 0.0f;
  
    for (size_t i = 0; i < count; i++) {
        CGImageRef image = CGImageSourceCreateImageAtIndex(source, i, NULL);
  
        duration += [self sd_frameDurationAtIndex:i source:source];
  
        [images addObject:[UIImage imageWithCGImage:image scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp]];
  
        CGImageRelease(image);
    }
  
    if (!duration) {
        duration = (1.0f / 10.0f) * count;
    }
  
    animatedImage = [UIImage animatedImageWithImages:images duration:duration];
  

  }

  CFRelease(source);

  return animatedImage;
  }