iOS展示gif图

展示本地gif图片
SDWebImage比较占内存,FLAnimatedImage不怎么占用内存

1.使用SDWebImage

1. 导入头文件
   #import "UIImage+GIF.h"
2. 设置gif图
   self.imageView.image = [UIImage sd_animatedGIFNamed:@"test"];
   也可以通过NSData导入
   + (UIImage *)sd_animatedGIFWithData:(NSData *)data

2.使用FLAnimatedImage

1. 导入头文件
   #import "FLAnimatedImage.h"
2. 设置gif图
   NSString *path = [[NSBundle mainBundle] pathForResource:@"test" ofType:@"gif"];
   NSData *data = [NSData dataWithContentsOfFile:path];
   FLAnimatedImage *image = [FLAnimatedImage animatedImageWithGIFData:data];
   self.imageView.animatedImage = image;

3.SDWebImage实现原理

使用UIImage + GIF分类

1.将gif图的每一帧导出为一个UIImage,并且算出每一帧的播放时间,将导出的image放入images数组中
2.使用+ animatedImageWithImages: duration: 方法创建image,参数为第一步的images数组和播放总时长
3.设置UIImageView的image时用sd_animatedGIFNamed:方法即可展示gif

方法1: 通过NSData获取gif的UIImage

方法名:+ (UIImage )sd_animatedGIFWithData:(NSData *)data;

1. 获取gif数据,及其帧数
2. 获取每帧的像素位图,求出每帧的播放时间
3. 按照屏幕分辨率生成UIImage并放入数组
4. 通过+ animatedImageWithImages: duration:生成UIImage
   + (UIImage *)sd_animatedGIFWithData:(NSData *)data {
   if (!data) {
   return nil;
   }
   //通过CFData读取gif文件的数据
   CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
   //获取gif文件的帧数
   size_t count = CGImageSourceGetCount(source);
   UIImage *animatedImage;
   if (count <= 1) {
   animatedImage = [[UIImage alloc] initWithData:data];
   }
   else {//大于一张图片时
   NSMutableArray *images = [NSMutableArray array];
   //设置gif播放的时间
   NSTimeInterval duration = 0.0f;
   for (size_t i = 0; i < count; i++) {
   //获取gif指定帧的像素位图
   CGImageRef image = CGImageSourceCreateImageAtIndex(source, i, NULL);
   if (!image) {
   continue;
   }
   //获取每张图的播放时间
   duration += [self sd_frameDurationAtIndex:i source:source];
   [images addObject:[UIImage imageWithCGImage:image scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp]];
   CGImageRelease(image);
   }
   if (!duration) {//如果播放时间为空
   duration = (1.0f / 10.0f) * count;
   }
   animatedImage = [UIImage animatedImageWithImages:images duration:duration];
   }
   CFRelease(source);
   return animatedImage;
   }

方法2:获取指定帧的image的播放时间

方法名:+ (float)sd_frameDurationAtIndex:(NSUInteger)index source:(CGImageSourceRef)source

1. 获取指定帧图片的属性字典
2. 获取图片的gif属性字典
3. 获取每一帧的播放时间(如果小于0.1,设置为0.1)
   + (float)sd_frameDurationAtIndex:(NSUInteger)index source:(CGImageSourceRef)source {
   float frameDuration = 0.1f;
   //获取这一帧图片的属性字典
   CFDictionaryRef cfFrameProperties = CGImageSourceCopyPropertiesAtIndex(source, index, nil);
   NSDictionary *frameProperties = (__bridge NSDictionary *)cfFrameProperties;
   //获取gif属性字典
   NSDictionary *gifProperties = frameProperties[(NSString *)kCGImagePropertyGIFDictionary];
   //获取这一帧持续的时间
   NSNumber *delayTimeUnclampedProp = gifProperties[(NSString *)kCGImagePropertyGIFUnclampedDelayTime];
   if (delayTimeUnclampedProp) {
   frameDuration = [delayTimeUnclampedProp floatValue];
   }
   else {
   NSNumber *delayTimeProp = gifProperties[(NSString *)kCGImagePropertyGIFDelayTime];
   if (delayTimeProp) {
   frameDuration = [delayTimeProp floatValue];
   }
   }
   //如果帧数小于0.1,则指定为0.1
   if (frameDuration < 0.011f) {
   frameDuration = 0.100f;
   }
   CFRelease(cfFrameProperties);
   return frameDuration;
   }

方法3:通过图片的Name获取UIImage

方法名:+ (UIImage *)sd_animatedGIFNamed:(NSString *)name;

1. 根据屏幕分辨率给图片自动加后缀(@2x)
2. 从mainBundle中获取Data数据
3. 调用方法 + sd_animatedGIFWithData:
   + (UIImage *)sd_animatedGIFNamed:(NSString *)name {
   //判断屏幕分辨率
   CGFloat scale = [UIScreen mainScreen].scale;
   if (scale > 1.0f) {
   NSString *retinaPath = [[NSBundle mainBundle] pathForResource:[name stringByAppendingString:@"@2x"] ofType:@"gif"];
   NSData *data = [NSData dataWithContentsOfFile:retinaPath];
   if (data) {
   return [UIImage sd_animatedGIFWithData:data];
   }
   NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:@"gif"];
   data = [NSData dataWithContentsOfFile:path];
   if (data) {
   return [UIImage sd_animatedGIFWithData:data];
   }
   return [UIImage imageNamed:name];
   }
   else {
   NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:@"gif"];
   NSData *data = [NSData dataWithContentsOfFile:path];
   if (data) {
   return [UIImage sd_animatedGIFWithData:data];
   }
   return [UIImage imageNamed:name];
   }
   }

方法4:对gif按比例进行缩放

方法名:- (UIImage *)sd_animatedImageByScalingAndCroppingToSize:(CGSize)size;

1. 获取较大的缩放比例值,宽高等比缩放
2. 调整位置,使缩放后的图居中
3. 遍历self.images, 将图片缩放后导出放入数组
4. 通过animatedImageWithImages:duration:返回image
   - (UIImage *)sd_animatedImageByScalingAndCroppingToSize:(CGSize)size {
   if (CGSizeEqualToSize(self.size, size) || CGSizeEqualToSize(size, CGSizeZero)) {
   return self;
   }
   CGSize scaledSize = size;
   CGPoint thumbnailPoint = CGPointZero;
   //获取较大的缩放比例值,宽高等比缩放
   CGFloat widthFactor = size.width / self.size.width;
   CGFloat heightFactor = size.height / self.size.height;
   CGFloat scaleFactor = (widthFactor > heightFactor) ? widthFactor : heightFactor;
   scaledSize.width = self.size.width * scaleFactor;
   scaledSize.height = self.size.height * scaleFactor;
   //调整位置,使缩放后的图居中
   if (widthFactor > heightFactor) {
   thumbnailPoint.y = (size.height - scaledSize.height) * 0.5;
   }
   else if (widthFactor < heightFactor) {
   thumbnailPoint.x = (size.width - scaledSize.width) * 0.5;
   }
   //遍历self.images, 将图片缩放后导出放入数组
   NSMutableArray *scaledImages = [NSMutableArray array];
   for (UIImage *image in self.images) {
   UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
   [image drawInRect:CGRectMake(thumbnailPoint.x, thumbnailPoint.y, scaledSize.width, scaledSize.height)];
   UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
   [scaledImages addObject:newImage];
   UIGraphicsEndImageContext();
   }
   return [UIImage animatedImageWithImages:scaledImages duration:self.duration];
   }