标签：
判断图片是否缓存
NSURL *url = [NSURL URLWithString:[model.content objectForKey:@"image"]]; //请求网络地址数据的同步方法 //因为这个方法在子线程(全局队列)中执行,所以不需要考虑死线程的问题 SDWebImageManager *manager = [SDWebImageManager sharedManager]; [manager diskImageExistsForURL:url]; if ([manager diskImageExistsForURL:url]) { LOG(@"11111") self.speakImage = [[manager imageCache] imageFromDiskCacheForKey:url.absoluteString]; }else{ LOG(@"3333333") NSData *data = [NSData dataWithContentsOfURL:url]; self.speakImage = [UIImage imageWithData:data]; }
/**
获取网络图片的Size, 先通过文件头来获取图片大小
如果失败 会下载完整的图片Data 来计算大小 所以最好别放在主线程
如果你有使用SDWebImage就会先看下 SDWebImage有缓存过改图片没有
支持文件头大小的格式 png、gif、jpg http://www.cocoachina.com/bbs/read.php?tid=165823
*/
+(CGSize)downloadImageSizeWithURL:(id)imageURL;
//讨厌警告
-(id)diskImageDataBySearchingAllPathsForKey:(id)key{return nil;}
+(CGSize)downloadImageSizeWithURL:(id)imageURL
{
NSURL* URL = nil;
if([imageURL isKindOfClass:[NSURL class]]){
URL = imageURL;
}
if([imageURL isKindOfClass:[NSString class]]){
URL = [NSURL URLWithString:imageURL];
}
if(URL == nil)
return CGSizeZero;
NSString* absoluteString = URL.absoluteString;
#ifdef dispatch_main_sync_safe
if([[SDImageCache sharedImageCache] diskImageExistsWithKey:absoluteString])
{
UIImage* image = [[SDImageCache sharedImageCache] imageFromMemoryCacheForKey:absoluteString];
if(!image)
{
NSData* data = [[SDImageCache sharedImageCache] performSelector:@selector(diskImageDataBySearchingAllPathsForKey:) withObject:URL.absoluteString];
image = [UIImage imageWithData:data];
}
if(!image)
{
return image.size;
}
}
#endif
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:URL];
NSString* pathExtendsion = [URL.pathExtension lowercaseString];
CGSize size = CGSizeZero;
if([pathExtendsion isEqualToString:@"png"]){
size = [self downloadPNGImageSizeWithRequest:request];
}
else if([pathExtendsion isEqual:@"gif"])
{
size = [self downloadGIFImageSizeWithRequest:request];
}
else{
size = [self downloadJPGImageSizeWithRequest:request];
}
if(CGSizeEqualToSize(CGSizeZero, size))
{
NSData* data = [NSURLConnection sendSynchronousRequest:[NSURLRequest requestWithURL:URL] returningResponse:nil error:nil];
UIImage* image = [UIImage imageWithData:data];
if(image)
{
#ifdef dispatch_main_sync_safe
[[SDImageCache sharedImageCache] storeImage:image recalculateFromImage:YES imageData:data forKey:URL.absoluteString toDisk:YES];
#endif
size = image.size;
}
}
return size;
}
+(CGSize)downloadPNGImageSizeWithRequest:(NSMutableURLRequest*)request
{
[request setValue:@"bytes=16-23" forHTTPHeaderField:@"Range"];
NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
if(data.length == 8)
{
int w1 = 0, w2 = 0, w3 = 0, w4 = 0;
[data getBytes:&w1; range:NSMakeRange(0, 1)];
[data getBytes:&w2; range:NSMakeRange(1, 1)];
[data getBytes:&w3; range:NSMakeRange(2, 1)];
[data getBytes:&w4; range:NSMakeRange(3, 1)];
int w = (w1 << 24) + (w2 << 16) + (w3 << 8) + w4;
int h1 = 0, h2 = 0, h3 = 0, h4 = 0;
[data getBytes:&h1; range:NSMakeRange(4, 1)];
[data getBytes:&h2; range:NSMakeRange(5, 1)];
[data getBytes:&h3; range:NSMakeRange(6, 1)];
[data getBytes:&h4; range:NSMakeRange(7, 1)];
int h = (h1 << 24) + (h2 << 16) + (h3 << 8) + h4;
return CGSizeMake(w, h);
}
return CGSizeZero;
}
+(CGSize)downloadGIFImageSizeWithRequest:(NSMutableURLRequest*)request
{
[request setValue:@"bytes=6-9" forHTTPHeaderField:@"Range"];
NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
if(data.length == 4)
{
short w1 = 0, w2 = 0;
[data getBytes:&w1; range:NSMakeRange(0, 1)];
[data getBytes:&w2; range:NSMakeRange(1, 1)];
short w = w1 + (w2 << 8);
short h1 = 0, h2 = 0;
[data getBytes:&h1; range:NSMakeRange(2, 1)];
[data getBytes:&h2; range:NSMakeRange(3, 1)];
short h = h1 + (h2 << 8);
return CGSizeMake(w, h);
}
return CGSizeZero;
}
+(CGSize)downloadJPGImageSizeWithRequest:(NSMutableURLRequest*)request
{
[request setValue:@"bytes=0-209" forHTTPHeaderField:@"Range"];
NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
if ([data length] <= 0x58) {
return CGSizeZero;
}
if ([data length] < 210) {// 肯定只有一个DQT字段
short w1 = 0, w2 = 0;
[data getBytes:&w1; range:NSMakeRange(0x60, 0x1)];
[data getBytes:&w2; range:NSMakeRange(0x61, 0x1)];
short w = (w1 << 8) + w2;
short h1 = 0, h2 = 0;
[data getBytes:&h1; range:NSMakeRange(0x5e, 0x1)];
[data getBytes:&h2; range:NSMakeRange(0x5f, 0x1)];
short h = (h1 << 8) + h2;
return CGSizeMake(w, h);
} else {
short word = 0x0;
[data getBytes:&word; range:NSMakeRange(0x15, 0x1)];
if (word == 0xdb) {
[data getBytes:&word; range:NSMakeRange(0x5a, 0x1)];
if (word == 0xdb) {// 两个DQT字段
short w1 = 0, w2 = 0;
[data getBytes:&w1; range:NSMakeRange(0xa5, 0x1)];
[data getBytes:&w2; range:NSMakeRange(0xa6, 0x1)];
short w = (w1 << 8) + w2;
short h1 = 0, h2 = 0;
[data getBytes:&h1; range:NSMakeRange(0xa3, 0x1)];
[data getBytes:&h2; range:NSMakeRange(0xa4, 0x1)];
short h = (h1 << 8) + h2;
return CGSizeMake(w, h);
} else {// 一个DQT字段
short w1 = 0, w2 = 0;
[data getBytes:&w1; range:NSMakeRange(0x60, 0x1)];
[data getBytes:&w2; range:NSMakeRange(0x61, 0x1)];
short w = (w1 << 8) + w2;
short h1 = 0, h2 = 0;
[data getBytes:&h1; range:NSMakeRange(0x5e, 0x1)];
[data getBytes:&h2; range:NSMakeRange(0x5f, 0x1)];
short h = (h1 << 8) + h2;
return CGSizeMake(w, h);
}
} else {
return CGSizeZero;
}
}
}
检测SDWebImage有没有缓存图片 IOS 获取网络图片大小
标签：
原文地址：http://www.cnblogs.com/Sucri/p/4718579.html
