react-native/Libraries/Image/RCTGIFImageDecoder.m

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

#import "RCTGIFImageDecoder.h"

#import <ImageIO/ImageIO.h>
#import <MobileCoreServices/MobileCoreServices.h>
#import <QuartzCore/QuartzCore.h>

#import "RCTUtils.h"

@implementation RCTGIFImageDecoder

RCT_EXPORT_MODULE()

- (BOOL)canDecodeImageData:(NSData *)imageData
{
  char header[7] = {};
  [imageData getBytes:header length:6];

  return !strcmp(header, "GIF87a") || !strcmp(header, "GIF89a");
}

- (RCTImageLoaderCancellationBlock)decodeImageData:(NSData *)imageData size:(CGSize)size scale:(CGFloat)scale resizeMode:(UIViewContentMode)resizeMode completionHandler:(RCTImageLoaderCompletionBlock)completionHandler
{
  CGImageSourceRef imageSource = CGImageSourceCreateWithData((CFDataRef)imageData, NULL);
  NSDictionary *properties = (__bridge_transfer NSDictionary *)CGImageSourceCopyProperties(imageSource, NULL);
  NSUInteger loopCount = [properties[(id)kCGImagePropertyGIFDictionary][(id)kCGImagePropertyGIFLoopCount] unsignedIntegerValue];

  size_t imageCount = CGImageSourceGetCount(imageSource);
  NSTimeInterval duration = 0;
  NSMutableArray *delays = [NSMutableArray arrayWithCapacity:imageCount];
  NSMutableArray *images = [NSMutableArray arrayWithCapacity:imageCount];
  for (size_t i = 0; i < imageCount; i++) {
    CGImageRef image = CGImageSourceCreateImageAtIndex(imageSource, i, NULL);
    NSDictionary *frameProperties = (__bridge_transfer NSDictionary *)CGImageSourceCopyPropertiesAtIndex(imageSource, i, NULL);
    NSDictionary *frameGIFProperties = frameProperties[(id)kCGImagePropertyGIFDictionary];

    const NSTimeInterval kDelayTimeIntervalDefault = 0.1;
    NSNumber *delayTime = frameGIFProperties[(id)kCGImagePropertyGIFUnclampedDelayTime] ?: frameGIFProperties[(id)kCGImagePropertyGIFDelayTime];
    if (delayTime == nil) {
      if (i == 0) {
        delayTime = @(kDelayTimeIntervalDefault);
      } else {
        delayTime = delays[i - 1];
      }
    }

    const NSTimeInterval kDelayTimeIntervalMinimum = 0.02;
    if (delayTime.floatValue < (float)kDelayTimeIntervalMinimum - FLT_EPSILON) {
      delayTime = @(kDelayTimeIntervalDefault);
    }

    duration += delayTime.doubleValue;
    delays[i] = delayTime;
    images[i] = (__bridge_transfer id)image;
  }
  CFRelease(imageSource);

  NSMutableArray *keyTimes = [NSMutableArray arrayWithCapacity:delays.count];
  NSTimeInterval runningDuration = 0;
  for (NSNumber *delayNumber in delays) {
    [keyTimes addObject:@(runningDuration / duration)];
    runningDuration += delayNumber.doubleValue;
  }

  [keyTimes addObject:@1.0];

  CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"contents"];
  animation.calculationMode = kCAAnimationDiscrete;
  animation.repeatCount = loopCount == 0 ? HUGE_VALF : loopCount;
  animation.keyTimes = keyTimes;
  animation.values = images;
  animation.duration = duration;
  completionHandler(nil, animation);

  return nil;
}

@end