生成的Gif太大了 - ObjectiveC

Question

我使用以下方法生成gif。

-(void)makeAnimatedGif:(NSArray *)imgArray {
    __block NSString *fileName = [NSString stringWithFormat:@"%ld",(long)[[NSDate date] timeIntervalSince1970]];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        //Do background work
        NSUInteger kFrameCount = imgArray.count;

        NSDictionary *fileProperties = @{
                                         (__bridge id)kCGImagePropertyGIFDictionary: @{
                                                 (__bridge id)kCGImagePropertyGIFLoopCount: @0, // 0 means loop forever
                                                 }
                                         };

        NSDictionary *frameProperties = @{
                                          (__bridge id)kCGImagePropertyGIFDictionary: @{
                                                  (__bridge id)kCGImagePropertyGIFDelayTime: @0.02f, // a float (not double!) in seconds, rounded to centiseconds in the GIF data
                                                  }
                                          };

        NSURL *documentsDirectoryURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:YES error:nil];

        NSURL *fileURL = [documentsDirectoryURL URLByAppendingPathComponent:fileName];

        CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)fileURL, kUTTypeGIF, kFrameCount, NULL);
        CGImageDestinationSetProperties(destination, (__bridge CFDictionaryRef)fileProperties);

        for (NSUInteger i = 0; i < kFrameCount; i++) {
            @autoreleasepool {
                UIImage *image =[imgArray objectAtIndex:i];  //Here is the change
                if (image.CGImage) {
                    CGImageDestinationAddImage(destination, image.CGImage, (__bridge CFDictionaryRef)frameProperties);
                }
            }
        }

        if (!CGImageDestinationFinalize(destination)) {
            NSLog(@"failed to finalize image destination");
        }

        dispatch_async(dispatch_get_main_queue(), ^{
            //Update UI
            CFRelease(destination);
            [self manageGifWithUrl:fileURL];
        });
    });

}

我的gif问题是尺寸非常大。生成的gif的大小范围从40MB到90MB。我无法找到任何解决方案。

我的imgArray包含180张图片。有没有解决这个问题？