Ios 远程图像大小，无需下载

使用Obj-c/Cocoa-touch，我试图获得图像列表的图像大小，但我不想下载它们。 有什么简单的方法吗？我在其他语言中找到了一些解决方案，如，但我正在寻找一种更简单的方法

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谢谢

如果您只想获取图像文件的大小，您可以使用NSUrlConnection从HTTP服务器请求标题（无需下载图像文件），然后从标题中提取内容长度：以获取文件大小。在类中使用expectedContentLength方法，有关详细信息，请参阅。这仍然不容易。

这里是我用于此的UIImage类别。它是基于。一个主要警告是NSURLConnectionLegate被设置为NSURL本身，这在某些情况下可能会导致冲突。这还未完成（例如忽略文件URL…），但您可以看到它的发展方向

标题：

#import <UIKit/UIKit.h>

typedef void (^UIImageSizeRequestCompleted) (NSURL* imgURL, CGSize size);

@interface UIImage (RemoteSize)

+ (void) requestSizeFor: (NSURL*) imgURL completion: (UIImageSizeRequestCompleted) completion;

@end

#导入
typedef void（^UIImageSizeRequestCompleted）（NSURL*imgURL，CGSize）；
@接口UIImage（RemoteSize）
+（无效）请求大小用于：（NSURL*）完成图：（UIImageSizeRequestCompleted）完成图；
@结束

资料来源：

#import "UIImage+RemoteSize.h"

#import <objc/runtime.h>

static char *kSizeRequestDataKey = "NSURL.sizeRequestData";
static char *kSizeRequestTypeKey = "NSURL.sizeRequestType";
static char *kSizeRequestCompletionKey = "NSURL.sizeRequestCompletion";

typedef uint32_t dword;

@interface NSURL (RemoteSize)
@property (nonatomic, strong) NSMutableData* sizeRequestData;
@property (nonatomic, strong) NSString* sizeRequestType;
@property (nonatomic, copy) UIImageSizeRequestCompleted sizeRequestCompletion;
@end

@implementation NSURL (RemoteSize)

- (void) setSizeRequestCompletion: (UIImageSizeRequestCompleted) block {
    objc_setAssociatedObject(self, &kSizeRequestCompletionKey, block, OBJC_ASSOCIATION_COPY);
}

- (UIImageSizeRequestCompleted) sizeRequestCompletion {
    return objc_getAssociatedObject(self, &kSizeRequestCompletionKey);
}

- (void) setSizeRequestData:(NSMutableData *)sizeRequestData {
    objc_setAssociatedObject(self, &kSizeRequestDataKey, sizeRequestData, OBJC_ASSOCIATION_RETAIN);
}

- (NSMutableData*) sizeRequestData {
    return objc_getAssociatedObject(self, &kSizeRequestDataKey);
}

- (void) setSizeRequestType:(NSString *)sizeRequestType {
    objc_setAssociatedObject(self, &kSizeRequestTypeKey, sizeRequestType, OBJC_ASSOCIATION_RETAIN);
}

- (NSString*) sizeRequestType {
    return objc_getAssociatedObject(self, &kSizeRequestTypeKey);
}

#pragma mark - NSURLConnectionDelegate
- (void) connection: (NSURLConnection*) connection didReceiveResponse:(NSURLResponse *)response {
    [self.sizeRequestData setLength: 0];    //Redirected => reset data
}

- (void) connection: (NSURLConnection*) connection didReceiveData:(NSData *)data {
    NSMutableData* receivedData = self.sizeRequestData;

    if( !receivedData ) {
        receivedData = [NSMutableData data];
        self.sizeRequestData = receivedData;
    }

    [receivedData appendData: data];

    //Parse metadata
    const unsigned char* cString = [receivedData bytes];
    const NSInteger length = [receivedData length];

    const char pngSignature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
    const char bmpSignature[2] = {66, 77};
    const char gifSignature[2] = {71, 73}; 
    const char jpgSignature[2] = {255, 216};

    if(!self.sizeRequestType ) {
        if( memcmp(pngSignature, cString, 8) == 0 ) {
            self.sizeRequestType = @"PNG";
        }
        else if( memcmp(bmpSignature, cString, 2) == 0 ) {
            self.sizeRequestType = @"BMP";
        }
        else if( memcmp(jpgSignature, cString, 2) == 0 ) {
            self.sizeRequestType = @"JPG";
        }
        else if( memcmp(gifSignature, cString, 2) == 0 ) {
            self.sizeRequestType = @"GIF";
        }
    }

    if( [self.sizeRequestType isEqualToString: @"PNG"] ) {
        char type[5];
        int offset = 8;

        dword chunkSize = 0;
        int chunkSizeSize = sizeof(chunkSize);

        if( offset+chunkSizeSize > length ) 
            return;

        memcpy(&chunkSize, cString+offset, chunkSizeSize);
        chunkSize = OSSwapInt32(chunkSize);
        offset += chunkSizeSize;

        if( offset + chunkSize > length ) 
            return;

        memcpy(&type, cString+offset, 4); type[4]='\0';
        offset += 4;

        if( strcmp(type, "IHDR") == 0 ) {   //Should always be first
            dword width = 0, height = 0;
            memcpy(&width, cString+offset, 4);
            offset += 4;
            width = OSSwapInt32(width);

            memcpy(&height, cString+offset, 4);
            offset += 4;
            height = OSSwapInt32(height);

            if( self.sizeRequestCompletion ) {
                self.sizeRequestCompletion(self, CGSizeMake(width, height));
            }

            self.sizeRequestCompletion = nil;

            [connection cancel];
        }
    }
    else if( [self.sizeRequestType isEqualToString: @"BMP"] ) {
        int offset = 18;
        dword width = 0, height = 0;
        memcpy(&width, cString+offset, 4);
        offset += 4;

        memcpy(&height, cString+offset, 4);
        offset += 4;

        if( self.sizeRequestCompletion ) {
            self.sizeRequestCompletion(self, CGSizeMake(width, height));
        }

        self.sizeRequestCompletion = nil;

        [connection cancel];
    }
    else if( [self.sizeRequestType isEqualToString: @"JPG"] ) {
        int offset = 4;
        dword block_length = cString[offset]*256 + cString[offset+1];

        while (offset<length) {
            offset += block_length;

            if( offset >= length )
                break;
            if( cString[offset] != 0xFF )
                break;
            if( cString[offset+1] == 0xC0 ||
                cString[offset+1] == 0xC1 ||
                cString[offset+1] == 0xC2 ||
                cString[offset+1] == 0xC3 ||
                cString[offset+1] == 0xC5 ||
                cString[offset+1] == 0xC6 ||
                cString[offset+1] == 0xC7 ||
                cString[offset+1] == 0xC9 ||
                cString[offset+1] == 0xCA ||
                cString[offset+1] == 0xCB ||
                cString[offset+1] == 0xCD ||
                cString[offset+1] == 0xCE ||
                cString[offset+1] == 0xCF ) {

                dword width = 0, height = 0;

                height = cString[offset+5]*256 + cString[offset+6];
                width = cString[offset+7]*256 + cString[offset+8];

                if( self.sizeRequestCompletion ) {
                    self.sizeRequestCompletion(self, CGSizeMake(width, height));
                }

                self.sizeRequestCompletion = nil;

                [connection cancel];

            }
            else {
                offset += 2;
                block_length = cString[offset]*256 + cString[offset+1];
            }

        }
    }
    else if( [self.sizeRequestType isEqualToString: @"GIF"] ) {
        int offset = 6;
        dword width = 0, height = 0;
        memcpy(&width, cString+offset, 2);
        offset += 2;

        memcpy(&height, cString+offset, 2);
        offset += 2;

        if( self.sizeRequestCompletion ) {
            self.sizeRequestCompletion(self, CGSizeMake(width, height));
        }

        self.sizeRequestCompletion = nil;

        [connection cancel];
    }
}

- (void) connection: (NSURLConnection*) connection didFailWithError:(NSError *)error {
    if( self.sizeRequestCompletion ) 
        self.sizeRequestCompletion(self, CGSizeZero);
}

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse {
    return cachedResponse;
}

- (void) connectionDidFinishLoading: (NSURLConnection *)connection {
    // Basically, we failed to obtain the image size using metadata and the
    // entire image was downloaded...

    if(!self.sizeRequestData.length) {
        self.sizeRequestData = nil;
    }
    else {
        //Try parse to UIImage
        UIImage* image = [UIImage imageWithData: self.sizeRequestData];

        if( self.sizeRequestCompletion && image) {
            self.sizeRequestCompletion(self, [image size]);
            return;
        }
    }

    self.sizeRequestCompletion(self, CGSizeZero);
}

@end

@implementation UIImage (RemoteSize)

+ (void) requestSizeFor: (NSURL*) imgURL completion: (UIImageSizeRequestCompleted) completion {

    if( [imgURL isFileURL] ) {
        //Load from file stream
    }
    else {
        imgURL.sizeRequestCompletion = completion;

        NSURLRequest* request = [NSURLRequest requestWithURL: imgURL];
        NSURLConnection* conn = [NSURLConnection connectionWithRequest: request delegate: imgURL];
        [conn scheduleInRunLoop: [NSRunLoop mainRunLoop] forMode: NSDefaultRunLoopMode];
        [conn start];
    }
}

@end

#导入“UIImage+RemoteSize.h”
#进口
静态字符*kSizeRequestDataKey=“NSURL.sizeRequestData”；
静态字符*kSizeRequestTypeKey=“NSURL.sizeRequestType”；
静态字符*kSizeRequestCompletionKey=“NSURL.sizeRequestCompletion”；
类型定义uint32_t dword；
@接口NSURL（RemoteSize）
@属性（非原子，强）NSMutableData*sizeRequestData；
@属性（非原子，强）NSString*sizeRequestType；
@属性（非原子，副本）UIImageSizeRequestCompleted SizeRequestCompleted；
@结束
@实现NSURL（RemoteSize）
-（void）setSizeRequestCompletion:（UIImageSizeRequestCompleted）块{
objc_setAssociatedObject（self，&ksizereRequestCompletionKey，block，objc_ASSOCIATION_COPY）；
}
-（UIImageSizeRequestCompleted）sizeRequestCompletion{
返回objc_getAssociatedObject（self和ksizereRequestCompletionKey）；
}
-（void）setSizeRequestData:（NSMutableData*）sizeRequestData{
objc_setAssociatedObject（self和kSizeRequestDataKey、sizeRequestData、objc_ASSOCIATION_RETAIN）；
}
-（NSMutableData*）大小请求数据{
返回objc_getAssociatedObject（self和ksizereRequestDataKey）；
}
-（void）setSizeRequestType:（NSString*）sizeRequestType{
objc_setAssociatedObject（self和kSizeRequestTypeKey、sizeRequestType、objc_ASSOCIATION_RETAIN）；
}
-（NSString*）sizeRequestType{
返回objc_getAssociatedObject（self和ksizereRequestTypeKey）；
}
#pragma标记-NSURLConnectionLegate
-（void）连接：（NSURLConnection*）连接DidReceiverResponse：（NSURResponse*）响应{
[self.sizeRequestData setLength:0]；//重定向=>重置数据
}
-（void）连接：（NSURLConnection*）连接didReceiveData:（NSData*）数据{
NSMutableData*receivedData=self.sizeRequestData；
如果（！receivedData）{
接收数据=[NSMutableData]；
self.sizeRequestData=receivedData；
}
[接收数据附录数据：数据]；
//分析元数据
const unsigned char*cString=[receivedData bytes]；
const NSInteger length=[receivedData length]；
const char pngSignature[8]={137,80,78,71,13,10,26,10}；
常量字符bmpSignature[2]={66,77}；
常量字符签名[2]={71,73}；
const char jpgSignature[2]={255，216}；
如果（！self.sizeRequestType）{
if（memcmp（pngSignature，cString，8）=0）{
self.sizeRequestType=@“PNG”；
}
else if（memcmp（bmpSignature，cString，2）=0）{
self.sizeRequestType=@“BMP”；
}
else if（memcmp（jpgSignature，cString，2）=0）{
self.sizeRequestType=@“JPG”；
}
else if（memcmp（gifSignature，cString，2）=0）{
self.sizeRequestType=@“GIF”；
}
}
if（[self.sizeRequestType IsequalString:@“PNG”]）{
字符类型[5]；
整数偏移=8；
dword chunkSize=0；
int chunkSizeSize=sizeof（chunkSize）；
如果（偏移量+块大小大小>长度）
返回；
memcpy（&chunkSize，cString+offset，chunkSizeSize）；
chunkSize=OSSwapInt32（chunkSize）；
偏移量+=chunkSizeSize；
如果（偏移量+块大小>长度）
返回；
memcpy（&type，cString+offset，4）；type[4]='\0'；
偏移量+=4；
if（strcmp（type，“IHDR”）==0）{//应始终位于第一位
dword宽度=0，高度=0；
memcpy（&width，cString+offset，4）；
偏移量+=4；
宽度=OSSwapInt32（宽度）；
memcpy（&height，cString+offset，4）；
偏移量+=4；
高度=OSSwapInt32（高度）；
if（self.sizeRequestCompletion）{
self.sizeRequestCompletion（self，CGSizeMake（宽度、高度））；
}
self.sizeRequestCompletion=nil；
[连接取消]；
}
}
else if（[self.sizeRequestType IsequalString:@“BMP”]）{
整数偏移=18；
dword宽度=0，高度=0；
memcpy（&width，cString+offset，4）；
偏移量+=4；
memcpy（&height，cString+offset，4）；
偏移量+=4；
if（self.sizeRequestCompletion）{
self.sizeRequestCompletion（self，CGSizeMake（宽度、高度））；
}
self.sizeRequestCompletion=nil；
[连接取消]；
}
else if（[self.sizeRequestType IsequalString:@“JPG”]）{
整数偏移=4；
dword块_长度=cString[offset]*256+cString[offset+1]；
while（偏移量=长度）
打破
如果（cString[偏移量]！=0xFF）
打破
如果（cString[偏移量+1]==0xC0||
cString[偏移量+1]==0xC1||
cString[偏移量+1]==0xC2||
cString[偏移量+1]==0xC3||
cString[偏移量+1]==0xC5||
cString[偏移量+1]==0xC6||
cString[offset+1]==0x