iOS开发——根据Url 获取图片尺寸

转自：http://www.oschina.net/code/snippet_2248391_53038




// 根据图片url获取图片尺寸

+(CGSize)getImageSizeWithURL:(id)imageURL

{

    NSURL* URL = nil;

    if([imageURL isKindOfClass:[NSURLclass]]){

        URL = imageURL;

    }

    if([imageURL isKindOfClass:[NSStringclass]]){

        URL = [NSURLURLWithString:imageURL];

    }

    if(URL == nil)

        returnCGSizeZero;                  // url不正确返回CGSizeZero

     

    NSMutableURLRequest*request = [[NSMutableURLRequestalloc] initWithURL:URL];

    NSString* pathExtendsion = [URL.pathExtension lowercaseString];

     

    CGSize size = CGSizeZero;

    if([pathExtendsion isEqualToString:@"png"]){

        size =  [selfgetPNGImageSizeWithRequest:request];

    }

    elseif([pathExtendsion isEqual:@"gif"])

    {

        size =  [selfgetGIFImageSizeWithRequest:request];

    }

    else{

        size = [selfgetJPGImageSizeWithRequest:request];

    }

    if(CGSizeEqualToSize(CGSizeZero, size))                    // 如果获取文件头信息失败,发送异步请求请求原图

    {

        NSData* data = [NSURLConnectionsendSynchronousRequest:[NSURLRequestrequestWithURL:URL] returningResponse:nilerror:nil];

        UIImage* image = [UIImageimageWithData:data];

        if(image)

        {

            size = image.size;

        }

    }

    returnsize;

}

//  获取PNG图片的大小

+(CGSize)getPNGImageSizeWithRequest:(NSMutableURLRequest*)request

{

    [request setValue:@"bytes=16-23"forHTTPHeaderField:@"Range"];

    NSData* data = [NSURLConnectionsendSynchronousRequest:request returningResponse:nilerror:nil];

    if(data.length == 8)

    {

        intw1 = 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)];

        intw = (w1 << 24) + (w2 << 16) + (w3 << 8) + w4;

        inth1 = 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)];

        inth = (h1 << 24) + (h2 << 16) + (h3 << 8) + h4;

        returnCGSizeMake(w, h);

    }

    returnCGSizeZero;

}

//  获取gif图片的大小

+(CGSize)getGIFImageSizeWithRequest:(NSMutableURLRequest*)request

{

    [request setValue:@"bytes=6-9"forHTTPHeaderField:@"Range"];

    NSData* data = [NSURLConnectionsendSynchronousRequest:request returningResponse:nilerror:nil];

    if(data.length == 4)

    {

        shortw1 = 0, w2 = 0;

        [data getBytes:&w1 range:NSMakeRange(0, 1)];

        [data getBytes:&w2 range:NSMakeRange(1, 1)];

        shortw = w1 + (w2 << 8);

        shorth1 = 0, h2 = 0;

        [data getBytes:&h1 range:NSMakeRange(2, 1)];

        [data getBytes:&h2 range:NSMakeRange(3, 1)];

        shorth = h1 + (h2 << 8);

        returnCGSizeMake(w, h);

    }

    returnCGSizeZero;

}

//  获取jpg图片的大小

+(CGSize)getJPGImageSizeWithRequest:(NSMutableURLRequest*)request

{

    [request setValue:@"bytes=0-209"forHTTPHeaderField:@"Range"];

    NSData* data = [NSURLConnectionsendSynchronousRequest:request returningResponse:nilerror:nil];

     

    if([data length] <= 0x58) {

        returnCGSizeZero;

    }

     

    if([data length] < 210) {// 肯定只有一个DQT字段

        shortw1 = 0, w2 = 0;

        [data getBytes:&w1 range:NSMakeRange(0x60, 0x1)];

        [data getBytes:&w2 range:NSMakeRange(0x61, 0x1)];

        shortw = (w1 << 8) + w2;

        shorth1 = 0, h2 = 0;

        [data getBytes:&h1 range:NSMakeRange(0x5e, 0x1)];

        [data getBytes:&h2 range:NSMakeRange(0x5f, 0x1)];

        shorth = (h1 << 8) + h2;

        returnCGSizeMake(w, h);

    }else{

        shortword = 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

                shortw1 = 0, w2 = 0;

                [data getBytes:&w1 range:NSMakeRange(0xa5, 0x1)];

                [data getBytes:&w2 range:NSMakeRange(0xa6, 0x1)];

                shortw = (w1 << 8) + w2;

                shorth1 = 0, h2 = 0;

                [data getBytes:&h1 range:NSMakeRange(0xa3, 0x1)];

                [data getBytes:&h2 range:NSMakeRange(0xa4, 0x1)];

                shorth = (h1 << 8) + h2;

                returnCGSizeMake(w, h);

            }else{// 一个DQT字段

                shortw1 = 0, w2 = 0;

                [data getBytes:&w1 range:NSMakeRange(0x60, 0x1)];

                [data getBytes:&w2 range:NSMakeRange(0x61, 0x1)];

                shortw = (w1 << 8) + w2;

                shorth1 = 0, h2 = 0;

                [data getBytes:&h1 range:NSMakeRange(0x5e, 0x1)];

                [data getBytes:&h2 range:NSMakeRange(0x5f, 0x1)];

                shorth = (h1 << 8) + h2;

                returnCGSizeMake(w, h);

            }

        }else{

            returnCGSizeZero;

        }

    }

}