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:[NSURL

class]]){

        URL
= imageURL;

    }

    if([imageURL
isKindOfClass:[NSString

class]]){

        URL
= [NSURL

URLWithString:imageURL];

    }

    if(URL
== nil)

        return

CGSizeZero;                  //
url不正确返回CGSizeZero

     

    NSMutableURLRequest

*request = [[NSMutableURLRequest

alloc] initWithURL:URL];

    NSString*
pathExtendsion = [URL.pathExtension lowercaseString];

     

    CGSize
size = CGSizeZero;

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

        size
=  [self

getPNGImageSizeWithRequest:request];

    }

    else

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

    {

        size
=  [self

getGIFImageSizeWithRequest:request];

    }

    else{

        size
= [self

getJPGImageSizeWithRequest: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 = [NSURLConnection

sendSynchronousRequest:[NSURLRequest

requestWithURL:URL] returningResponse:nil

error:nil];

        UIImage*
image = [UIImage

imageWithData:data];

        if(image)

        {

            size
= image.size;

        }

    }

    return

size;

}

// 
获取PNG图片的大小

+(CGSize)getPNGImageSizeWithRequest:(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;

}

// 
获取gif图片的大小

+(CGSize)getGIFImageSizeWithRequest:(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;

}

// 
获取jpg图片的大小

+(CGSize)getJPGImageSizeWithRequest:(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;

        }

    }

}