顯示gif圖通常使用的方式如下：
1.使用UIImageView;
2,使用sdwebImage；
3,使用YYImage;
4,使用webview；
但是顯示方式無非兩種：
1：先一次性把gif圖解析成多個圖片，然后輪流播放這些圖片,比如使用UIImageView和sdwebImage；這種方式因為要保存解析后的圖片，所以占用內(nèi)存比較高；
2，播放到哪一張圖片時，去gif圖中解析對應(yīng)的這張照片，用完就釋放，不占用內(nèi)存，比如YYImage和webview，但是因為要頻繁地解析圖片，當照片分辨率很高時，會造成cpu占用率高，導致手機發(fā)熱；
如果使用的gif圖分辨率較低，影響還不是很大，個人測試當使用的gif圖分辨率為1280*720，gif圖大于8M，數(shù)量超過6個時，使用sdwebImage會由于內(nèi)存暴漲導致崩潰；而使用YYImage雖然不會導致內(nèi)存暴漲，但是cpu占用率過高導致手機溫度上升；
綜合考慮：不能使用內(nèi)存暴增導致程序崩潰的方式，只能使用YYImage或者webview去顯示；既然是因為圖片分辨率高導致手機溫度升高，如果把圖片分辨率降低，就可以解決問題了。具體操作如下：
1，從相冊選擇圖片后，使用ALAssetsLibrary取到圖片的原始數(shù)據(jù)：
//獲取選擇的圖片
-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info {
[picker dismissViewControllerAnimated:YES completion:nil];
[MeetHUD showLoadingTo:self.view animated:YES];
__weak typeof(self)weakSelf = self;
dispatch_async(dispatch_get_global_queue(0, 0), ^{
NSURL *imageURL = [info valueForKey:UIImagePickerControllerReferenceURL];
NSString *assetString = [imageURL absoluteString];
__strong typeof(weakSelf)strongSelf = weakSelf;
ALAssetsLibrary *assetLibrary = [[ALAssetsLibrary alloc]init];
[assetLibrary assetForURL:imageURL resultBlock:^(ALAsset *asset) {
ALAssetRepresentation *re = nil;
if([assetString hasSuffix:@"GIF"] || [assetString hasSuffix:@"gif"]){
re = [asset representationForUTI:(__bridge NSString *)kUTTypeGIF];
} else {
re = [asset defaultRepresentation];
}
NSUInteger size = [re size];
uint8_t *buffer = malloc(size);
NSError *error;
NSUInteger bytes = [re getBytes:buffer fromOffset:0 length:size error:&error];
NSData *data = [NSData dataWithBytes:buffer length:bytes];//這個就是選取的圖片的原二進制數(shù)據(jù)
free(buffer);
NSData*scaleData = [self DataToScaleGifData: data];
} failureBlock:^(NSError *error) {
}];
});
}
2，解析出gif圖中的每張圖片；
-(NSData*)DataToScaleGifData:(NSData*)data{
CGImageSourceRef gifSource = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
size_t gifCount = CGImageSourceGetCount(gifSource);
NSMutableArray *scaleImgArray = [NSMutableArray array];
NSTimeInterval totalDuration = 0;//播放的總時長
float scale = 1;
float imgSize = data.length/1024/1024;
//小于2M不進行縮放，2M帶4M縮放60%，4M到8M縮放40%，超過8M縮放20%
if(imgSize <= 2){
scale = 1;
} else if (imgSize > 2 && imgSize < 4){
scale = 0.6;
} else if(imgSize >= 4 && imgSize < 8){
scale = 0.4;
} else {
scale = 0.2;
}
float imgWidth = 0;
float imgHeight = 0;
for (size_t i = 0; i< gifCount; i++) {
CGImageRef imageRef = CGImageSourceCreateImageAtIndex(gifSource, i, NULL);
imgWidth = CGImageGetWidth(imageRef);
imgHeight = CGImageGetHeight(imageRef);
UIImage *uiImage = [UIImage imageWithCGImage:imageRef];
if(scale == 1){
[scaleImgArray addObject:uiImage];
} else {
UIImage *scaleImg = [[self class] imageCompresswithsimple:uiImage scaledtosize:CGSizeMake(imgWidth*scale, imgHeight*scale)];
[scaleImgArray addObject:scaleImg];
}
NSTimeInterval duration = [MeetVirtualHeaderTool gifImageDeleyTime:gifSource index:i];
totalDuration += duration;
CGImageRelease(imageRef);
}
CFRelease(gifSource);
//重新生成一個縮放后的gif圖data
NSData *resultData = [[self class] creategifWithImgArray:scaleImgArray duration:totalDuration];
return resultData;
}
圖片縮放方法如下：
+ (UIImage*)imageCompresswithsimple:(UIImage*)image scaledtosize:(CGSize)size{
UIGraphicsBeginImageContext(size);
[image drawInRect:CGRectMake(0,0,size.width,size.height)];
UIImage* newimage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newimage;
}
重新生成縮放后的gif圖data方法：
+ (NSData *)creategifWithImgArray:(NSArray *)imgArray duration:(float)duration{
// 1.獲取圖片數(shù)據(jù)
NSMutableArray *imageArray = [NSMutableArray arrayWithArray:imgArray];
//每幀時長
float perDuration = duration*1.0/imgArray.count;
// 2.創(chuàng)建gif文件
NSArray *document = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docString = [document objectAtIndex:0];
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *pathString = [docString stringByAppendingString:@"/gif"];
[fileManager createDirectoryAtPath:pathString withIntermediateDirectories:YES attributes:nil error:nil];
NSString *path = [pathString stringByAppendingString:@"test1.gif"];
// 3.配置gif屬性
CGImageDestinationRef destion;
// 將 path 映射成 CFURLRef 的路徑
CFURLRef url = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)path, kCFURLPOSIXPathStyle, false);
destion = CGImageDestinationCreateWithURL(url, kUTTypeGIF, imageArray.count, NULL);
// [mutDict setObject:[NSNumber numberWithFloat:perDuration] forKey:kCGImagePropertyGIFUnclampedDelayTime];
NSDictionary *dict = [NSDictionary dictionaryWithObject:[NSMutableDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithFloat:perDuration],(NSString *)kCGImagePropertyGIFDelayTime, nil] forKey:(NSString *)kCGImagePropertyGIFDelayTime];
NSMutableDictionary *mutDict = [NSMutableDictionary dictionaryWithCapacity:2];
[mutDict setObject:[NSNumber numberWithBool:YES] forKey:(NSString *)kCGImagePropertyGIFHasGlobalColorMap];
[mutDict setObject:(NSString *)kCGImagePropertyColorModelRGB forKey:(NSString *)kCGImagePropertyColorModel];
[mutDict setObject:[NSNumber numberWithInt:8] forKey:(NSString *)kCGImagePropertyDepth];
[mutDict setObject:[NSNumber numberWithInt:0] forKey:(NSString *)kCGImagePropertyGIFLoopCount];
NSDictionary *gifPropertyDict = [NSDictionary dictionaryWithObject:mutDict forKey:(NSString *)kCGImagePropertyGIFDictionary];
CGImageDestinationSetProperties(destion, (__bridge CFDictionaryRef)gifPropertyDict);
// 單幀添加到gif
for (UIImage *image in imageArray) {
CGImageDestinationAddImage(destion, image.CGImage, (__bridge CFDictionaryRef)dict);
}
CGImageDestinationFinalize(destion);
CFRelease(destion);
NSData *gifData = [NSData dataWithContentsOfFile:path];
NSError *err;
[fileManager removeItemAtPath:path error:&err];
if(err == nil){
}
return gifData;
}
3,使用縮放后的data，不管是使用yyImage還是webView，cpu的使用率都降低了，手機也不再發(fā)熱了，能夠解決問題。
4，如果需要把原始數(shù)據(jù)傳給服務(wù)器，可以再發(fā)送數(shù)據(jù)時，對縮小后的data進行放大處理，然后再發(fā)送給服務(wù)器，但是這種方式會造成gif圖顯示模糊，可以保留原始數(shù)據(jù)進行發(fā)送，也可以發(fā)送壓縮后的數(shù)據(jù)。
