一 .计算NSData
[[NSData alloc] initWithContentsOfURL:<#(nonnull NSURL *)#>]
转化为图片,然后进行宽高计算.
二.SD下载计算
sd_setImageWithURL:[NSURL URLWithString:url] completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
计算十张图片耗时:
123.252071 ms
三.取图片URL的字节值
image.png
CF_INLINE uint16_t FNKSwapWebIntToInt16(uint16_t arg) {
return CFSwapInt16BigToHost(arg);
}
CF_INLINE uint16_t FNKSwapWebIntToInt32(uint32_t arg) {
return CFSwapInt32BigToHost(arg);
}
typedef enum : NSUInteger {
FNKImagePrefetcherImageType_PNG,
FNKImagePrefetcherImageType_GIF,
FNKImagePrefetcherImageType_JPG,
FNKImagePrefetcherImageType_BMP,
FNKImagePrefetcherImageType_UNKOWN
} FNKImagePrefetcherImageType;
#define UN_FETCHED_IMAGE_SIZE CGSizeMake(CGFLOAT_MIN, CGFLOAT_MIN)
@interface FNKImagePrefetcher ()<NSURLSessionDataDelegate>
@property (nonatomic, strong) NSURLSession *session;
@property (nonatomic, strong) NSOperationQueue *queue;
@property (nonatomic, strong) NSMutableData *downloadData;
@property (nonatomic, assign) FNKImagePrefetcherImageType imageType;
@property (nonatomic, assign) CGSize imageSize;
@property (nonatomic, assign) NSInteger maxTimerinterval;
@end
@implementation FNKImagePrefetcher {
dispatch_semaphore_t _lock;
}
- (instancetype)initWithUrl:(NSURL *)url {
return [self initWithUrl:url timeInterval:1.5];
}
- (instancetype)initWithUrl:(NSURL *)url timeInterval:(NSInteger) timeInterval {
if (!url) return nil;
self = [super init];
if (self) {
_maxTimerinterval = timeInterval;
_imageUrl = url;
_imageSize = UN_FETCHED_IMAGE_SIZE;
_imageType = FNKImagePrefetcherImageType_UNKOWN;
}
return self;
}
- (NSOperationQueue *)queue {
if (!_queue) {
_queue = [[NSOperationQueue alloc] init];
_queue.name = @"com.FNK.image.prefetcher.queue";
}
return _queue;
}
- (CGSize)fetchImageSize {
return [self downloadDataWithUrl:_imageUrl];
}
- (CGSize )downloadDataWithUrl:(NSURL *)url {
if (!_session) {
NSURLSessionConfiguration *config = NSURLSessionConfiguration.defaultSessionConfiguration;
config.requestCachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
_session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:self.queue];
}
NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:3];
NSURLSessionDataTask *task = [_session dataTaskWithRequest:request];
_lock = dispatch_semaphore_create(0);
[task resume];
dispatch_time_t waitTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(_maxTimerinterval * NSEC_PER_SEC));
dispatch_semaphore_wait(_lock, waitTime);
return _imageSize;
}
#pragma -mark NSURLSessionDataDelegate
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask
didReceiveData:(NSData *)data {
if (!data) return;
if (!_downloadData) {
_downloadData = [[NSMutableData alloc] init];
}
[_downloadData appendData:data];
if (_downloadData.length < 2) return;
if (_imageType == FNKImagePrefetcherImageType_UNKOWN) {
self.imageType = [self fetchImageTtypeFormData:_downloadData];
}
// 解析数据
switch (_imageType) {
case FNKImagePrefetcherImageType_JPG:
{
_imageSize = [self fetchHWFromJPGData:_downloadData];
}
break;
case FNKImagePrefetcherImageType_PNG:
{
_imageSize = [self fetchHWFromPNGData:_downloadData];
}
break;
case FNKImagePrefetcherImageType_BMP:
{
_imageSize = [self fetchHWFromGIFData:_downloadData];
}
break;
case FNKImagePrefetcherImageType_GIF:
{
_imageSize = [self fetchHWFromGIFData:_downloadData];
}
break;
default:
break;
}
// 获取到提前数据结束
if (!CGSizeEqualToSize(self.imageSize, UN_FETCHED_IMAGE_SIZE)) {
[dataTask cancel];
dispatch_semaphore_signal(_lock);
}
}
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
didCompleteWithError:(nullable NSError *)error {
if (CGSizeEqualToSize(self.imageSize, UN_FETCHED_IMAGE_SIZE)) {
if (_downloadData) {
UIImage *image = [UIImage imageWithData:_downloadData];
if (image) _imageSize = image.size;
}
}
dispatch_semaphore_signal(_lock);
}
- (FNKImagePrefetcherImageType)fetchImageTtypeFormData:(NSData *)data {
if(data.length < 2) return FNKImagePrefetcherImageType_UNKOWN;
UInt8 word0 = 0x0, word1 = 0x0;
[data getBytes:&word0 range:NSMakeRange(0, 1)];
[data getBytes:&word1 range:NSMakeRange(1, 1)];
if (word0 == 0xFF && word1 == 0xD8) {
return FNKImagePrefetcherImageType_JPG;
}else if (word0 == 0x89 && word1 == 0x50) {
return FNKImagePrefetcherImageType_PNG;
}else if (word0 == 0x47 && word1 == 0x49) {
return FNKImagePrefetcherImageType_GIF;
}else if (word0 == 0x42 && word1 == 0x4D) {
return FNKImagePrefetcherImageType_BMP;
}
return FNKImagePrefetcherImageType_UNKOWN;
}
- (CGSize)fetchHWFromJPGData:(NSData *)data {
CGSize size = CGSizeZero;
// jpeg 文件格式头中有JFTF也有EXIF，EXIF相对复杂，具体头部结构可以见https://blog.csdn.net/ryfdizuo/article/details/41250775
// FF D8 FF E0 (XX XX 这两字节为长度) ('JF' 'TF' 转为ascll码值)
UInt8 word0 = 0x0, word1 = 0x0, word2 = 0x0, word3 = 0x0;
[data getBytes:&word0 range:NSMakeRange(0, 1)];
[data getBytes:&word1 range:NSMakeRange(1, 1)];
[data getBytes:&word2 range:NSMakeRange(2, 1)];
[data getBytes:&word3 range:NSMakeRange(3, 1)];
if (word0 == 0xFF && word1 == 0xD8 && word2 == 0xFF && word3 == 0xE0) {
UInt8 c0 = 0, c1 = 0, c2 = 0, c3 = 0;
[data getBytes:&c0 range:NSMakeRange(6, 1)];
[data getBytes:&c1 range:NSMakeRange(7, 1)];
[data getBytes:&c2 range:NSMakeRange(8, 1)];
[data getBytes:&c3 range:NSMakeRange(9, 1)];
if (c0 == 'J' && c1 == 'F' && c2 == 'I' && c3 == 'F') {
UInt16 block_length = 0;
[data getBytes:&block_length range:NSMakeRange(4, 2)];
block_length = FNKSwapWebIntToInt16(block_length);
int i = 4;
do {
i += block_length;
if (i > data.length) {
break;
}
UInt8 aW = 0x0;
[data getBytes:&aW range:NSMakeRange(i, 1)];
if (aW != 0xFF) {
break;
}
UInt8 ca = 0x0;
[data getBytes:&ca range:NSMakeRange(i+1, 1)];
if (ca >= 0xC0 && ca<= 0xC3) {
/**
图片信息段 FF CO (xx xx 该段长度) XX(抛弃字节，不用) (HH HH 高度) (WW WW 宽度) ...后面是其他信息。
这里宽高段和 png gif 等都不一样，jpg 是高在前
*/
UInt16 w = 0, h = 0;
[data getBytes:&h range:NSMakeRange(i + 5, 2)];
[data getBytes:&w range:NSMakeRange(i + 7, 2)];
w = FNKSwapWebIntToInt16(w);
h = FNKSwapWebIntToInt16(h);
size = CGSizeMake(w, h);
break;
}else {
i += 2;
[data getBytes:&block_length range:NSMakeRange(i, 2)];
block_length = FNKSwapWebIntToInt16(block_length);
}
} while (i < data.length);
}
}
return size;
}
- (CGSize)fetchHWFromPNGData:(NSData *)data {
/**
png 头格式
89 50 4E 47 0D 0A 1A 0A (4byte IDHR) (4Byte CHUNKTYPE) (4Byte WIDTH) (4Byte HEIGHT) ....
至少需要24bytes
*/
if (data.length < 24) return CGSizeZero;
UInt32 w = 0, h = 0;
[data getBytes:&w range:NSMakeRange(16, 4)];
[data getBytes:&h range:NSMakeRange(20, 4)];
w = FNKSwapWebIntToInt32(w);
h = FNKSwapWebIntToInt32(h);
return CGSizeMake(w, h);
}
- (CGSize)fetchHWFromGIFData:(NSData *)data {
/**
GIF 头格式
47 49 46 38 39 61 (2Byte WIDTH) (2Byte HEIGHT) ....
至少需要10bytes
*/
if (data.length < 10) return CGSizeZero;
UInt16 w = 0, h = 0;
[data getBytes:&w range:NSMakeRange(6, 2)];
[data getBytes:&h range:NSMakeRange(8, 2)];
return CGSizeMake(w, h);
}
- (CGSize)fetchHWFromBMPData:(NSData *)data {
/**
BMP 头格式可见http://www.fastgraph.com/help/bmp_os2_header_format.html
*/
if (data.length < 29) return CGSizeZero;
UInt32 length = 0;
[data getBytes:&length range:NSMakeRange(14, 4)];
length = FNKSwapWebIntToInt32(length);
if (length == 12) {
UInt16 w = 0, h = 0;
[data getBytes:&w range:NSMakeRange(18, 2)];
[data getBytes:&h range:NSMakeRange(820, 2)];
w = FNKSwapWebIntToInt16(w);
h = FNKSwapWebIntToInt16(h);
return CGSizeMake(w, h);
}else {
UInt32 w = 0, h = 0;
[data getBytes:&w range:NSMakeRange(18, 4)];
[data getBytes:&h range:NSMakeRange(22, 4)];
w = FNKSwapWebIntToInt32(w);
h = FNKSwapWebIntToInt32(h);
return CGSizeMake(w, h);
}
return CGSizeZero;
}
@end
取十张图片计算耗时有点大.
1483.412027 ms~4000ms
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