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; }
}
}