+ (void)imageToWebP:(UIImage *)image quality:(CGFloat)quality alpha:(CGFloat)alpha preset:(WebPPreset)preset
    completionBlock:(void (^)(NSData *result))completionBlock
       failureBlock:(void (^)(NSError *error))failureBlock;

+ (void)imageWithWebP:(NSString *)filePath
      completionBlock:(void (^)(UIImage *result))completionBlock
         failureBlock:(void (^)(NSError *error))failureBlock;

- (UIImage *)imageByApplyingAlpha:(CGFloat)alpha;

// quality value is [0, 100]
// alpha value is [0, 1]
[UIImage imageToWebP:[UIImage imageNamed:@"demo.jpg"] quality:quality alpha:alpha preset:WEBP_PRESET_DEFAULT completionBlock:^(NSData *result) {
  NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString *webPPath = [paths[0] stringByAppendingPathComponent:@"image.webp"];
  if (![result writeToFile:webPPath atomically:YES]) {
    NSLog(@"Failed to save file");
  }
} failureBlock:^(NSError *error) {
  NSLog(@"%@", error.localizedDescription);
}];

// quality value is [0, 100]
// alpha value is [0, 1]
[UIImage imageToWebP:[UIImage imageNamed:@"demo.jpg"] quality:quality alpha:alpha
 preset:WEBP_PRESET_DEFAULT
 configBlock:^(WebPConfig *config) {
    config->sns_strength = 50.0f;
    config->filter_strength = 0.0f;
    config->method = 2;
    config->preprocessing = 0;
    config->filter_sharpness = 0;
    config->thread_level = 1;
 }
 completionBlock:^(NSData *result) {
  NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString *webPPath = [paths[0] stringByAppendingPathComponent:@"image.webp"];
  if (![result writeToFile:webPPath atomically:YES]) {
    NSLog(@"Failed to save file");
  }
} failureBlock:^(NSError *error) {
  NSLog(@"%@", error.localizedDescription);
}];

[UIImage imageWithWebP:@"/path/to/file" completionBlock:^(UIImage *result) {
  UIImageView *myImageView = [[UIImageView alloc] initWithImage:result];
}failureBlock:^(NSError *error) {
  NSLog(@"%@", error.localizedDescription);
}];

//alpha value is [0, 1]
UIImage *transparencyImage = [[UIImage imageNamed:image.jpg] imageByApplyingAlpha:0.5];